you could even take out the driveshaft completely and try again on the jack stands. that way you'll know for sure if the driveshaft or the adapter have something to do with it
Long confirmed that the vibration itself is coming from the driveshaft as shown in previous under-car footage. I'm not in question of where it's coming from, I'm in question of what's causing it. Also have already changed out the diff, diff bushings, axles, and wheel bearings.
You should analyze an audio recording of the vibration to get the exact frequency of it, then compare it to the RPM of various drive line elements and look for a match.
Damn you beat me to it. I had nasty noises when mine were loose, although no vibrations. The only thing is that that isnt his subframe, rather the brace. Can a piece if rattling metal really cause such harsh vibrations?
The BMW driveshafts has a support bearing near to the gearbox. Maybe the gearbox output bearing didn't designed to hokd the whole shaft weight and rotation inertia so the bearing in gearbox is starting to rattle. The idea of disconnecting dr8veshaft and repeat the jackstand test seems a good idea but maybe only the shaft with gearbox together causing this.
That's what I'm thinking. Long shafts can bend /vibrate at high speed. The bearing is there to reduce the sag /whipping of driveshaft. It's like a rope, you can't tighten it straight horizontally, they will always sag in the middle.
@@remytv and I saw that his shaft has the sleeve section almost in the middle so that definietly has to have a tiny play even if you can't feel with hand. It needs a support bearing in front of that.
Have you calculated the driveshaft critical speed? The ZF transmission is shorter than the Mazda 5/6 speed trans meaning a longer driveshaft. Longer driveshaft = lowered rpm critical speed= shaft will be looking to "whip" and create severe vibration; in fact BMW E36 and E46 use 2 separate driveshaft for this reason. Please share the following info: Mazda driveshaft length (yoke cross to yoke cross) and tube OD, ZF kit driveshaft length(yoke cross to yoke cross) and tube OD. Will be able to estimate with these numbers
CV joints are located at the end of each axle. There is both an outer and inner joint. When the inner CV joint is damaged or begins to fail, you will notice your car vibrating under hard acceleration. As it gets worse, the minor vibrations turn to violent shaking when under load.
TheCarPassionChannel sorry just now realized that after watching your other videos on this problem I’ve seen a lot in my time with cars. I have a question does the vibration stay at a certain speed or does it continue getting worse the faster you go. I hope you figure it out what ever the problem might be.
After seeing all the cameras you were going to set up, I thought for sure you were going to do closeups of each component of the drivetrain, in order to ascertain which might be the cause of the vibrations. This seems like it would possibly help isolate the problem, since the shotgun approach hasn't solved the problem, yet. I do appreciate this video and it's a good step in your puzzle. You've definitely ruled out a few things. Good luck, looking forward to the next one!
That's already been located - via under car footage posted in previous videos. The driveshaft is the source of the vibration, we just don't know what is causing it.
I'm pretty sure the forward section of the two-piece driveshafts that these transmissions are designed for, are not angled to the transmission in any way. In other words, the driveshaft is perfectly aligned with the transmission. The output flange bearings of the transmission may not be robust enough to handle any angle change. On a one-piece driveshaft, the angles of BOTH ends impart loads into the shaft that the transmission output flange bearing must deal with. A two-piece shaft, with a center hanger bearing, aligns the front shaft perfectly with the transmission and isolates the forces generated by the differential angle. I think a properly set up two-piece driveshaft may be your solution.
From watching your diagnosis vidoes and reading your comments, I believe there is combination of multiple "significant" issues all playing a part in this. Chassis and components stiffness/alignment all playing gremlins with each other, I think your process of elimination isn't over yet. Can't wait for when you resolve this Gregg 👌
I got to say your channel to me is the best. The fact that it's all about Miata makes it the best and your videos top the other Miata videos out there. I feel like there are some TH-camrs out there that kind of started with Miata and ended up focusing on other cars. like tomorrow if I clicked on a video of yours and you were working on a S2000 or something I would be disappointed. Also if you had an astronomical amount of money and you were just throwing all high-end Parts in your car that would be unobtainable for your viewers that would also make it a less desirable Channel. I love the fact that what you do to your Miata I can do to my Miata. Keep it up
My NB2 (Hard s) has a bracing vaguely where the getrag270 mounts to the chassis via the OEM BMW bushing. I remember once forgetting to fix one of the two bolts and the whole car was resonating like maniac at highway speed. To my understanding, the tunnel it's super sensitive to resonance, how about trying to take the support out (making the transmission rest on jack)? Saying this because the OEM E36 stock brace looks waaay beefier then the kmiata. It wouldn't solve the shaft vibrating on itself but at least it won't resonate the whole chassis like mad. Just my 0.02$
I had the same feeling about this being some sort of resonance problem and I know Miatas can be prone to that in general. It seems to be pretty smooth right up to a certain point when the two or more normal vibrations seem to resonate right at about 80MPH. I would try the jack and separately, attach a small weight on the driveshaft to purposely through it out of balance and see if that changes the resonate frequency.
Hello! Brilliant channel - I think the problem you are experiencing may be the result of resonance in the drivetrain i.e. the inherant resonance of a rotating length fixed at two points. In the MX5 design and development book the Mazda engineers noted a resonance referred to as nodal bending which occured at 43Hz, they overcame it by positioning the two end points (engine and diff mounts) at the null points of bending so limited vibration would be transfered to the chassis. By adding the gearbox support I think you might have introduced a coupling point to the chassis far from the nulls. I don't know how to solve it perfectly without having a PPF to support the gearbox but any balancing of the rotating assembly would make it less severe. Good luck and keep up the excellent work! Kind regards, Tom
I feel like your setup is not managing vibration properly that eventually builds up in the driveshaft. I really wonder what would happen if you try that same test, but secure the engine with an overhead mount. Some way to offload vibration from the engine. Then supply some extra dampening to the trans and the diff with a jack. If that removes it, that could be revealing.
GREG! Greetings from Scotland. I've had an idea. You've fitted the drivetrain upgrade kit which removes the PPF. With the Miata being a monocock, you have removed the member that links the front and rear rotating assemblies. Now the engine and gearbox and rear diff can send vibrations through the car individually where as with the PPF being fitted it absorbs that vibration and harmonises with the body. Could it be that the rear diffs harmonics are fighting the harmonics of the engine and gearbox causing the body to vibrate and by linking the two with a frame similar to the PPF will cure the problem?
The problem with this hypothesis is the loads of Miatas currently running no PPF, without issues. Not only with this kit, but with basically every other transmission and differential swap kit on the market.
@@TheCarPassionChannel I understand that, but it's likely that the body is vibrating and not the drive line. You've already proven that it's all balanced etcand done plenty testing to prove the drive line is in normal condition. All I am saying is that everyone's bodies are different, different seats, braces, roll bars etc, that could make the difference that allows the lack of PPF to cause the vibration or not. As a test, I would try adding a brace between the gearbox and the diff, or stiffen the car. Have you checked to see off the vibration changes with the roof off for example?
I mentioned this last video, I've had exactly the same vibration at motorway speeds with the PPF bolts essentially doing nothing (came loose) PPF is tight fit and wasn't a rattle, just vibration The transmission mounted to tunnel will always add NVH but there is a balance issue here, the vibrations between diff and engine are likely going through the chassis and not through what would be the ppf like you've said. Failing disconnecting the prop while it's up in air ( gearbox will leak ) you can't easily pin point it down, stiffened chassis will help ie frame rails but the cause is most likely the setup not using the PPF I'd be interested to know if the setups that are not having issues are using similar engine mounts, diff mounts and have any underside bracing, as rubber/poly engine mounts will have less NVH than fab 9 type, stock diff mounts and void fillers will have much less NVH than derlin or poly, especially ones that ditch the stop washers on the diff.
@@TheCarPassionChannel Have you thought about engine torque twisting the body at the transmission crossmember mount and causing the rear u-joint to be out of phase with the front driveshaft mount?
Hi Peter, Mechanical engineer here. I have both a Bmw and Miata of the same vintage, so I know them both well. I think it's a combination of several problems. High speed footage of trans/driveshaft would help. 1. why did you eliminate the rubber giubo at the output flange? You eliminated the torsional vibration damping. 2. Bmw has a center support bearing on the slip section of the shaft. 3. All that vibration from driveline getting transferred to the body as some have said. Hope this helps
Thanks for posting these Greg. I've been watching your videos for a couple years now and they've been really helpful. Your issue is really interesting, as are the methods you're using to diagnose it. So thanks, and I hope you get it fixed.
@thecarpassionchannel I’d pull the axels, repeat the test, pull the drive shaft, repeat the test, as it only gets worse with wheel speed it shouldn’t be super hard to pinpoint, but I know the frustration, with the driveshaft out, you’d be able to tell if it’s past the output, the driveshaft and diff would be the only remaining... could be the style yokes that cause the vibration..could be something in the diff. I’d just jiggle everything, put a jack under the diff and see if there is any play, could be the angles the driveshaft is in. I guess my only question is how many revolutions does the bmw shaft spin compared to a factory Miata trans and drive shaft? Would putting the same bmw diff in the car help? Does the bmw that the trans come out of ever have this problem? I’d get a piece of paper and start eliminating things/ while researching same swap setups, we have to get this figured out.
Greg. I just had a crazy thought. It could be a bent half shaft. Put the car back up on the stands, and disconnect the CV shafts, then run it up again. That will either prove or disprove a CV shaft problem. Of not, then disconnect the prop shaft and run it up again. That will isolate the problem a little further.
while driving down the road find the frequency of vibration. Might be able to narrow things down due to all the gear reductions. Since you already narrowed it down to post transmission, you might be able to tell if it is before or after the differential. -- just an idea
This is a similair problem which effected me and that is common within the S2000 community, that is related to aftermarket throwout and spigot bearings causing excess vibrations on the pressure plate and fly wheel which transfers down the driveline and is still present in neutral as it doesnot disengage the clutch fully . Even reputable brands such as Exedy have this issue. Went through a gearbox rebuild with brand new oem gearsets + another drive shaft only to find out the issue could of been resolved with OEM replacements of both the throwout and spigot bearings. (Extensive testing by the community points to the OEM parts being the only ones without the issue.) Not sure if this problem would effect the Getrags transmissions although might it be worth swapping them out as it looks like this isnt the last time your gonna have to drop that transmission :) Look up S2000 clutch buzz for more info, hope this helps, give us a shout out if it does lol
Same conclusion i came to aswell when trouble shooting my car which lead me to replace every other driveline compenent first. the issue turned out to be with the clutch fully despressed the throwout bearing did not not 100% disengage causing risidual friction on the disk damaging the fly wheel bearing which compounded the issue.
Also this issue is inherent from the throw out bearing being a "pull type" which will still cause vibration even when the engine seems to not be rotating as your transmission/drive shaft is still rotating and "rubbing" for lack of a better term via the pressureplate and clutch. Inmagine your transmission trying to spin freely but ever so slighty engages for split second causing resonant vibration which explains why it is still present when the engine is switched off. The reason why i mention the spigot bearing is that this is also the reason it happens in gear as well as out as a bad throw out bearing will also eventually damage it. Notice your rpms bouncing rather than going down smoothly when your switch off your engine
@@ThaiPham-pb2wv When the trans is in neutral, and the clutch is out, engine off, there is no spinning of any parts inside the bellhousing, everything is at a dead stop. If the engine is off, trans in gear, clutch in, then the input shaft and clutch disc are spinning which could create noise. This is also push type :)
@@TheCarPassionChannel Ah k cant speak for an push style throw out bearing here although it could still be a bad spigot bearing introducing reaonant vibrations as you put load into your gearbox/ drive shaft. Long shot but seeing as you've tried everything else its worth replacing next time your have the trans out, for a few dollars worth a shot if you have the opportunity
those driveshafts are supposed to have a center support normally although i know alot of people use 1 piece in e30s with getrags. could also be not having a rubber guibo on the output shaft mating to the driveshaft
2 piece driveshafts use a center support bearing, 1 piece systems do not. The Guibo is actually a possible solution to the problem, but may be difficult to pull off with a 1 piece shaft. That's something that's in the works.
TheCarPassionChannel Yeah that’s what I meant with the 2P system using the center support bearing I wonder how much vibration that takes out, assuming the vibration would be due to harmonic imbalance of rotation happening from the transmission through the driveshaft
I had a similar issue on a mustang one time and it ended up being both the rear rotors where warped. Also might want to get your rear axles checked. They could have got bent or slightly twisted causing them to be off balance.
My miata was making a noise that I could NOT find. Since I have an open diff I was able to get the rear wheels up to speed separately. It was really sketchy but I was able to pin point the noise to the driver side.
If you look at a cross section of the 260 gearbox you will see it has a different bearing setup on the output shaft compared to a gearbox with a slip yoke output shaft. The 260 was designed to use a center bearing on the tail shaft.
This is like a bass guitar that only buzzes on the 18th fret on the D string. Harmonics. Maybe. But I am hopeful this is a single component that is going to end up being located. Man you are a very methodical troubleshooter. This started after you put the bushings and the BMW transmission with the adapter kits if my memory is serving me.
I have the same vibration issue but on my s14 with a 1jz vvti and cd009 trans and z33 diff, I had my driveshaft rebalanced and it seemed to help a tiny bit but not really. The fastest I’ve gone in my car is 100 just because the vibrations feel so bad. I haven’t had time to try anything else. I do have solid bushings for the diff since it’s a conversion and my trans mount is polyurethane.
You're probably already looking into this, but I feel like a Guibo would solve this. Its meant to deal with driveline misalignment and vibrations in conjunction with the CSB.
That's a setup that KMiata and I are working on; the tricky part is figuring out a guibo setup using a 1 piece shaft since they have to have a zero degree operating angle. It's in the works though!
Thanks for the video. Maybe good to check if your subframe is not bent, check if the diff is in line with the driveshaft and if your axle shafts are straight and true. Also your front bolts of the subframe brace to the car are missing as others mention, but I would not expect them to be the source of the issue.
I have has similar issues with wheels out of balance, a bad wheel bearing, and a bad tire. Also, an old issue that goes back to the NA Miatas - they like lower tire pressure. Dropping to 26 lbs can eliminate some highway vibrations.
Greg, there's a tip I learnt in school that might help you, grab some hose clamps that will fit around your driveshaft and tighten them on, see if it changes the vibration, moving them up and down the driveshaft as well as twisting them. It could be possible that the driveshaft its self is balanced but possible slightly off centre when mounted?
If we wait patiently Greg will show us what the issue is. Greg I just did some searching. There are some DIY tricks for balancing your driveshaft. But also shops that do it. I am fairly certain you have explored these avenues but just in case. You are spinning stock shafts very fast. How fast do you have your tires spun when you get them balanced? Curious....
Have you been able to check the gearbox out put and diff input shafts are parallel? If they're not it will vibrate! I work with this stuff on industrial equipment
To be cheaper with it greg can go through with his knock sensor on megasquirt held at different positions along his driveline and view the direct sensor data to isolate the harmonic
Have you tried to put back the 6 speed and check driveshaft angles? Also might be that the Getrag is a little of center ti the diff. Its very strange, and I don't have any clue why the driveshaft have such severe vibration.
check geometry: gearbox output shaft must be parallel with diff input shaft, otherwise you can have variable angular speeds, The same applied to cv joints. This joints does not tolerate big angles
I thought you would shoot under the car, set cruise control at 80-100mph, and watch at various angles the drivetrain components and what could be harmonizing in such terrible fashion. Darn it Greg! Well, I can't wait to see what you've learned on the next one. Great videos buddy!
Here a thought.... now what if the transmission mount is vibrating the hole car from the rpm speed of the drive shaft of was there to holed the Tran and diff but also was to stiffen the chassis what if that could be the problem more power bigger transmission bigger components more vibration I know the trans has a damper and so dus the drive shaft but what if it just the trans mount
7:30 there is a bar that is not bolted down left of the exhaust hanger, is it rattling against the chassis maybe? Edit: just realized someone already pointed this out
dont have a clue here but from any car i ever worked on the drive shaft always had the slider part of the shaft mounted to the trans and the big part of the drive shaft mounted to the diff....which is not how its mounted here in this video
This might be ignorant of me but the bolts from the trans crossmember are laying directly on the trans with washers but wouldn't regardless metal doesn't isolatethe vibration. Wouldn't vibration move through the bolts into rest of the chassis?
I'm starting to suspect the transmission tunnel wasn't designed to dampen the high frequency vibrations of a high RPM driveline. Whatever the tiny BMW bushings don't absorb is possibly being transmitted through the body of the car. The PPF forced these vibrations to travel up and down the driveline all the way to the engine mounts and differential mounts. Now that vibration may be taking the path of least resistance straight into the center console? Perhaps some type of dampener or "weight" on the new transmission mount to absorb vibrations. I see these constantly on newer Chrysler built vehicles....on the body to frame bolts, on the exhaust, etc. Even seen them directly on the differential case.
at 7:00. Bolted mounts on the side to something?. Cross member with rubber isolators. Are those two mounts equally loaded? Or, in other words, is one carrying more weight than the other?
Is there any heat in the brakes after trying the tests? A while ago I had bad vibrations which were caused by contact between pad and disc. New disc pads and service on calipers fixed the problem.
May or may not be an issue, the diff looks like its mounted from the PPF to the chassis with no bushings, I know your setup has delrin diff bushings but if the diff is still mounted solidly to the chassis in other places, it may cause vibration?... it's weird because driveline vibes are usually at low speeds
Well I’m glad I changed from a 260 to a ZF 6-speed before this happened lol.. Good luck Greg, maybe the custom center support driveshaft can solve your issue.
@@bmxbarn15 maybe from a technical standpoint, but the mass majority of the community calls the shaft from the trans to the diff a drive shaft, and from the diff to the hubs axles or axle shafts... at least in the states.
That was an awesome analytical approach. Great job. Its gotta be a rotating mass thing...somewhere. It sounds/looks like you have eliminated tires/wheels, engine-related, and driveline. That leaves transmission, diff, axle shafts, and associated mounting stuff. What a bugger! Best wishes. If its not some weirdo "harmonics" thing where two different things are affecting each other at a certain speed, I'm sticking with transmission.....
It might be a diff issue. I just put in a torsen in mine with unknown mileage and I get pretty bad nvh noises around 75 80 mph. I'm thinking it might be a pinion to ring gear meshing issue but idk for sure. Granted it may be accentuated my using poly mount brushing but maybe try another diff? Maybe because the ppf isnt absorbing some of those vibrations anymore?
Have you tried the "stock BMW bushings" maybe that are too soft for a Miata application. Take a vid of the back of your transmission and the front of your differential and check for up and down, side to side movement.
I have same kind of issue.. It vibrates at 2700 rpm when you let the trottle of.. The driveshaft bearin has been replaced and the torsen diff has been shimmed.. Torsen cog wheel maby vibrates??
Try swapping those rubber transmission mount bushing for something hard, and see how that makes a difference. Like back on the jack stands and driving. The symptoms i would be predicting is slightly more vibration at low speed, and reduced vibration at high speed
Have you tried changing gearbox bushings/mounts for something with different stiffness? since vibrations are speed related, there should be something with that speed or frequency that causes it. And resonanting frequencies are determined by stiffness of elastic elements and damping. So I'd tried to replace all bushings with solid mounts at least temporary for testing. and if it will not help - have a look on structural rigidity of places where components are mounted. Maybe those are acting as springs in your case...
Could it have something to do with the fact that the transmission cross member is solidly mounted to the transmission tunnel? Thinking back to how Miata drive train components are mounted stock, no drive train component is that directly mounted to body work like that. Especially body work that is so non-structural (as I don't believe the transmission tunnel is). My theory is that vibration you are seeing in the drive line behind the output shaft are not being dampened enough by the transmission mounts and because the metal the transmission cross member is bolted into is rather thin, its causing the flimsier body to resonate at high speeds. Might be worth trying to switch to softer mounts or adding insulators between the transmission tunnel and the cross member.
This is similar what happened to my moms car about a year ago, the driveshaft was misaligned by about half a degree and that was enough to shake the hell out of the it at 60-65mph in 5th gear. The actual issue wasnt the actual driveshaft, but the driveshaft mounting point against the diff because at some point the car bottomed out and bent it. I'm not an engineer or a mechanic or anything but that was what I understood to be the issue and he showed me, replaced it, and it went away.
Pretty sure this is a resonant frequency issue with the drive shaft, by adding in the adaptor plate you will changing the vibration characteristics of the whole driveline. There's a lot of NVH engineering behind OE systems so there needs to be some further refinement. Consider changing the length of drive shaft as increasing the damping/bushing is only really covering up the issue. There must be some NVH specialists out there who can solve this with some modal analysis.
That’s what I thought too. Either design. Damper in the adaptor like the noze pulley or get the assembled driveline balanced and had a pin to make it is always assembled the same way
Another good one is you can fix your phone to different parts of your gearbox and diff and log the accelerometer data with any of the free apps. The vibration at the source should be thr strongest and you will have actual data to compare various systems.
Wheel bearing? Try the same test but only one axle at a time see if its only one side. you just have to isolate the vibration. the 96m i had done the same things at 55-60 and again around 90-100. it had a bent rims for a long time bore i had it.i replaced the axles and had the drive shaft balanced. sold the car never found the issue. think iv watched every video for the last 5 years. hope you figure it out.
Hi Greg. I haven't watched the whole video yet, but before i forget... My dad had a vibration issue on his car over 70 MPH and after much research and getting tyres re-balanced etc it turned out to be the Spigot Rings for his alloy wheels were something like 0.5mm too small overall. I didn't believe that this could cause such a big problem but it did! Might be worth looking into.
Not sure if you tried yet or talked about yet but what about disconnecting the drive shaft from the trans and run the test in 5th again? That may rule out the trans.
Hi Greg , I feel your pain. I think that the problem is related to where you put your supporting brackets for your gearbox. If it were me I would be mocking up the location of the geabox while supported on a jack with a lazer on a magnet or something at the back end. After 'clocking' the lazer for alignment - point the lazer at the centre of your diff and rotate the engine while adjusting the jack for good gearbox alignment. Thats the point at which to commit to putting holes in for your supporting brackets. I think your vibrations are related to an eccentic loading while your drive shaft is rotating. Theres no point in having a balanced drive shaft that isnt perfectly aligned. Happy to talk more about this... I'm used to be a cnc machinist and know the follies of having things that rotate fast that arent perfectly aligned and balanced
Couldn't you take the Axel's loose to check the diff? I have a 67 Chevy II. 350 350t trans and Ford 9 in rear end. It does the same thing vibrates at higher speeds. Almost positive it's somthing in the rear end. Haven't tore into it yet
This might be out of this world but if it’s possible I’d say try making an adapter for the driveshaft to the trans with bumpers inside to absorb vibrations. Something similar to what the bmw trans come with. Cause your drivetrain and engine are all stiff due to your bushings. Maybe if you have something in their to absorb more vibrations. Cause the CV joint probably only helps so much
Seems like you’ve tried quite a few s things with the driveshaft. I think the next step should be to experiment with different stiffness engine and transmission mounts. You should probably also try stiffer or softer diff mounts.
Hey Greg I don’t know if this could be it or not since you were saying there are others running this kit as well with no issue but when you look at how the trans bushings are setup technically since the bolt passing through is still sits both on the transmission and on the mount that is bolted to the body it still could be sending vibrations through it even with that bushing in the middle. Think about like the diff bushings and the motor mounts. The bushing completely isolates one part of the car where no metal is touching besides either the body or what is being mounted. Maybe try throwing some rubber on one side of those bolts to see if that might at least help a little bit
On the transmission bushings they are actually not through-bolts, it's a cylinder of rubber with a stud on each side, so they offer complete isolation :)
There are like two dozen comments saying its a wheel bearing or a cv axle, and *Greg literally says in this video* that they have been replaced. Good luck with your problem Greg. My money is on one of two issues: Two piece driveshaft, or trans internals. Dont forget the output shaft of the transmission is always spinning at driveshaft speed too, it could be trans internals (maybe some old bearings in the trans are allowing the output shaft to wobble in place?) either way, good luck with your gremlins dood
Can't win em all 😂 I've actually got a buddy with the same setup, and the same issue, he bought a built G260, all new bearings, and it didn't fix anything. So lucky for me, I didn't try a built box haha. Definitely heavily leaning towards driveshaft harmonics or something of the sort.
Did you test the connection of the trans to the car? The Bracket, the bushings, the chassis contact points? I mean the trans will vibrate and the miata structure is not engineered to take these loads at those (new) contact points. Great vids, keep em coming!
A tuned helmholtz resonator is used to eliminate a specific drone frequency. What is the equivalent for vibration frequency? Adding weight to a specific area? OEM's have NVH labs for this stuff and crazy smart people with PHD's in this. Not fair lolol. Goodluck man
Has the slip yoke engagement been investigated? To far pulled out would be bad at speed, just the tolerances within the slip splines could cause the shaft to come out of true.
In Sweden we have a saying "Trägen vinner".. which is from the north where people barely speaks (hence the shortness).. means "Stubborness wins".. just keep at it, it will show itself eventually!
You can always look into investing in some chassis ears they pick up sounds and vibrations and can be mounted anywhere by zip ties. Same stuff we us at my work to find noises or vibrations 👍
you could even take out the driveshaft completely and try again on the jack stands. that way you'll know for sure if the driveshaft or the adapter have something to do with it
Marco Franceschi that would also rule out anything to do with the rear end (diff) I would think
@@jarredcool4350 right!
Or without axles maybe? If that is possible🤷♂️
Long confirmed that the vibration itself is coming from the driveshaft as shown in previous under-car footage. I'm not in question of where it's coming from, I'm in question of what's causing it. Also have already changed out the diff, diff bushings, axles, and wheel bearings.
@@TheCarPassionChannel it was more of a: "while you're there" kind of test ;) Cheers Greg loving your work from Italy!
Car Passion Channel posts a video, everything stops for 10 minutes.
True that!
Everything stops but the vibrations in the Miata...
SUCH FACTS
drpiv Stopped studying for my exam tomorrow, here I am
@@Likethetacosauce sad but true
Turn on captions at 3:36😂
😂😂
nice
You wont regret it 😂
Hhahaahhaa
You should analyze an audio recording of the vibration to get the exact frequency of it, then compare it to the RPM of various drive line elements and look for a match.
7:28 put in your subframe brace bolts in
That could be a cause for the vibrations!
th-cam.com/video/dDshiu5um9g/w-d-xo.html this is what your brace is doing when its not bolted down
4:42 look at the brace solved you your problem
Deividas Juozaitis I don’t see anything at 4:42.
Damn you beat me to it. I had nasty noises when mine were loose, although no vibrations. The only thing is that that isnt his subframe, rather the brace. Can a piece if rattling metal really cause such harsh vibrations?
Been in the dumps last few weeks and I can't explain how much happy I was when I got the notification. Thanks Greg, thanks a lot
It's ya boi, Craig Yeeters
The BMW driveshafts has a support bearing near to the gearbox. Maybe the gearbox output bearing didn't designed to hokd the whole shaft weight and rotation inertia so the bearing in gearbox is starting to rattle. The idea of disconnecting dr8veshaft and repeat the jackstand test seems a good idea but maybe only the shaft with gearbox together causing this.
That's what I'm thinking. Long shafts can bend /vibrate at high speed. The bearing is there to reduce the sag /whipping of driveshaft. It's like a rope, you can't tighten it straight horizontally, they will always sag in the middle.
@@remytv and I saw that his shaft has the sleeve section almost in the middle so that definietly has to have a tiny play even if you can't feel with hand. It needs a support bearing in front of that.
The tupperware of water is obviously for detecting the distance of nearby dynosaurs.
Have you calculated the driveshaft critical speed? The ZF transmission is shorter than the Mazda 5/6 speed trans meaning a longer driveshaft. Longer driveshaft = lowered rpm critical speed= shaft will be looking to "whip" and create severe vibration; in fact BMW E36 and E46 use 2 separate driveshaft for this reason. Please share the following info: Mazda driveshaft length (yoke cross to yoke cross) and tube OD, ZF kit driveshaft length(yoke cross to yoke cross) and tube OD. Will be able to estimate with these numbers
CV joints are located at the end of each axle. There is both an outer and inner joint. When the inner CV joint is damaged or begins to fail, you will notice your car vibrating under hard acceleration. As it gets worse, the minor vibrations turn to violent shaking when under load.
I wish it was that simple but the car has new axles!
TheCarPassionChannel sorry just now realized that after watching your other videos on this problem I’ve seen a lot in my time with cars. I have a question does the vibration stay at a certain speed or does it continue getting worse the faster you go. I hope you figure it out what ever the problem might be.
Fun video idea: i kinda want a tour of your garage/tool layout and organization. Always like getting ideas for new things to try
After seeing all the cameras you were going to set up, I thought for sure you were going to do closeups of each component of the drivetrain, in order to ascertain which might be the cause of the vibrations. This seems like it would possibly help isolate the problem, since the shotgun approach hasn't solved the problem, yet. I do appreciate this video and it's a good step in your puzzle. You've definitely ruled out a few things. Good luck, looking forward to the next one!
That's already been located - via under car footage posted in previous videos. The driveshaft is the source of the vibration, we just don't know what is causing it.
I'm pretty sure the forward section of the two-piece driveshafts that these transmissions are designed for, are not angled to the transmission in any way. In other words, the driveshaft is perfectly aligned with the transmission. The output flange bearings of the transmission may not be robust enough to handle any angle change. On a one-piece driveshaft, the angles of BOTH ends impart loads into the shaft that the transmission output flange bearing must deal with. A two-piece shaft, with a center hanger bearing, aligns the front shaft perfectly with the transmission and isolates the forces generated by the differential angle. I think a properly set up two-piece driveshaft may be your solution.
This actually makes sense to me as well since my e30 has a carrier bearing on the prop shaft.
From watching your diagnosis vidoes and reading your comments, I believe there is combination of multiple "significant" issues all playing a part in this. Chassis and components stiffness/alignment all playing gremlins with each other, I think your process of elimination isn't over yet. Can't wait for when you resolve this Gregg 👌
That Initial D clip made my day 😁
I got to say your channel to me is the best. The fact that it's all about Miata makes it the best and your videos top the other Miata videos out there. I feel like there are some TH-camrs out there that kind of started with Miata and ended up focusing on other cars. like tomorrow if I clicked on a video of yours and you were working on a S2000 or something I would be disappointed. Also if you had an astronomical amount of money and you were just throwing all high-end Parts in your car that would be unobtainable for your viewers that would also make it a less desirable Channel. I love the fact that what you do to your Miata I can do to my Miata. Keep it up
My NB2 (Hard s) has a bracing vaguely where the getrag270 mounts to the chassis via the OEM BMW bushing. I remember once forgetting to fix one of the two bolts and the whole car was resonating like maniac at highway speed. To my understanding, the tunnel it's super sensitive to resonance, how about trying to take the support out (making the transmission rest on jack)? Saying this because the OEM E36 stock brace looks waaay beefier then the kmiata. It wouldn't solve the shaft vibrating on itself but at least it won't resonate the whole chassis like mad. Just my 0.02$
I had the same feeling about this being some sort of resonance problem and I know Miatas can be prone to that in general. It seems to be pretty smooth right up to a certain point when the two or more normal vibrations seem to resonate right at about 80MPH.
I would try the jack and separately, attach a small weight on the driveshaft to purposely through it out of balance and see if that changes the resonate frequency.
Hello! Brilliant channel - I think the problem you are experiencing may be the result of resonance in the drivetrain i.e. the inherant resonance of a rotating length fixed at two points. In the MX5 design and development book the Mazda engineers noted a resonance referred to as nodal bending which occured at 43Hz, they overcame it by positioning the two end points (engine and diff mounts) at the null points of bending so limited vibration would be transfered to the chassis. By adding the gearbox support I think you might have introduced a coupling point to the chassis far from the nulls. I don't know how to solve it perfectly without having a PPF to support the gearbox but any balancing of the rotating assembly would make it less severe. Good luck and keep up the excellent work! Kind regards, Tom
I feel like your setup is not managing vibration properly that eventually builds up in the driveshaft. I really wonder what would happen if you try that same test, but secure the engine with an overhead mount. Some way to offload vibration from the engine. Then supply some extra dampening to the trans and the diff with a jack. If that removes it, that could be revealing.
GREG! Greetings from Scotland. I've had an idea. You've fitted the drivetrain upgrade kit which removes the PPF. With the Miata being a monocock, you have removed the member that links the front and rear rotating assemblies. Now the engine and gearbox and rear diff can send vibrations through the car individually where as with the PPF being fitted it absorbs that vibration and harmonises with the body. Could it be that the rear diffs harmonics are fighting the harmonics of the engine and gearbox causing the body to vibrate and by linking the two with a frame similar to the PPF will cure the problem?
The problem with this hypothesis is the loads of Miatas currently running no PPF, without issues. Not only with this kit, but with basically every other transmission and differential swap kit on the market.
@@TheCarPassionChannel I understand that, but it's likely that the body is vibrating and not the drive line. You've already proven that it's all balanced etcand done plenty testing to prove the drive line is in normal condition. All I am saying is that everyone's bodies are different, different seats, braces, roll bars etc, that could make the difference that allows the lack of PPF to cause the vibration or not. As a test, I would try adding a brace between the gearbox and the diff, or stiffen the car. Have you checked to see off the vibration changes with the roof off for example?
I mentioned this last video, I've had exactly the same vibration at motorway speeds with the PPF bolts essentially doing nothing (came loose) PPF is tight fit and wasn't a rattle, just vibration
The transmission mounted to tunnel will always add NVH but there is a balance issue here, the vibrations between diff and engine are likely going through the chassis and not through what would be the ppf like you've said.
Failing disconnecting the prop while it's up in air ( gearbox will leak ) you can't easily pin point it down, stiffened chassis will help ie frame rails but the cause is most likely the setup not using the PPF
I'd be interested to know if the setups that are not having issues are using similar engine mounts, diff mounts and have any underside bracing, as rubber/poly engine mounts will have less NVH than fab 9 type, stock diff mounts and void fillers will have much less NVH than derlin or poly, especially ones that ditch the stop washers on the diff.
@@GmoLargey that makes two Greg 😜😁
@@TheCarPassionChannel Have you thought about engine torque twisting the body at the transmission crossmember mount and causing the rear u-joint to be out of phase with the front driveshaft mount?
Hi Peter,
Mechanical engineer here. I have both a Bmw and Miata of the same vintage, so I know them both well.
I think it's a combination of several problems. High speed footage of trans/driveshaft would help.
1. why did you eliminate the rubber giubo at the output flange? You eliminated the torsional vibration damping.
2. Bmw has a center support bearing on the slip section of the shaft.
3. All that vibration from driveline getting transferred to the body as some have said.
Hope this helps
Is the worst feeling when you doesnt find de problem! I wish you the best lucky possible!! You are each time near! Cheers man
Thanks for posting these Greg. I've been watching your videos for a couple years now and they've been really helpful. Your issue is really interesting, as are the methods you're using to diagnose it. So thanks, and I hope you get it fixed.
@thecarpassionchannel I’d pull the axels, repeat the test, pull the drive shaft, repeat the test, as it only gets worse with wheel speed it shouldn’t be super hard to pinpoint, but I know the frustration, with the driveshaft out, you’d be able to tell if it’s past the output, the driveshaft and diff would be the only remaining... could be the style yokes that cause the vibration..could be something in the diff. I’d just jiggle everything, put a jack under the diff and see if there is any play, could be the angles the driveshaft is in. I guess my only question is how many revolutions does the bmw shaft spin compared to a factory Miata trans and drive shaft? Would putting the same bmw diff in the car help? Does the bmw that the trans come out of ever have this problem? I’d get a piece of paper and start eliminating things/ while researching same swap setups, we have to get this figured out.
Greg. I just had a crazy thought. It could be a bent half shaft. Put the car back up on the stands, and disconnect the CV shafts, then run it up again. That will either prove or disprove a CV shaft problem. Of not, then disconnect the prop shaft and run it up again. That will isolate the problem a little further.
Yo thanks for the video Greg. It always makes my day when I see a new video in my feed.
Honored to be the 100,000th Subscriber. You really deserve it
I still have 881 to go! Thank you though haha
while driving down the road find the frequency of vibration. Might be able to narrow things down due to all the gear reductions. Since you already narrowed it down to post transmission, you might be able to tell if it is before or after the differential. -- just an idea
This is a similair problem which effected me and that is common within the S2000 community, that is related to aftermarket throwout and spigot bearings causing excess vibrations on the pressure plate and fly wheel which transfers down the driveline and is still present in neutral as it doesnot disengage the clutch fully . Even reputable brands such as Exedy have this issue. Went through a gearbox rebuild with brand new oem gearsets + another drive shaft only to find out the issue could of been resolved with OEM replacements of both the throwout and spigot bearings.
(Extensive testing by the community points to the OEM parts being the only ones without the issue.)
Not sure if this problem would effect the Getrags transmissions although might it be worth swapping them out as it looks like this isnt the last time your gonna have to drop that transmission :)
Look up S2000 clutch buzz for more info, hope this helps, give us a shout out if it does lol
Very likely issue, if the problem didn't occur with clutch and flywheel RPM at zero like it does in my case.
Same conclusion i came to aswell when trouble shooting my car which lead me to replace every other driveline compenent first. the issue turned out to be with the clutch fully despressed the throwout bearing did not not 100% disengage causing risidual friction on the disk damaging the fly wheel bearing which compounded the issue.
Also this issue is inherent from the throw out bearing being a "pull type" which will still cause vibration even when the engine seems to not be rotating as your transmission/drive shaft is still rotating and "rubbing" for lack of a better term via the pressureplate and clutch. Inmagine your transmission trying to spin freely but ever so slighty engages for split second causing resonant vibration which explains why it is still present when the engine is switched off. The reason why i mention the spigot bearing is that this is also the reason it happens in gear as well as out as a bad throw out bearing will also eventually damage it. Notice your rpms bouncing rather than going down smoothly when your switch off your engine
@@ThaiPham-pb2wv When the trans is in neutral, and the clutch is out, engine off, there is no spinning of any parts inside the bellhousing, everything is at a dead stop. If the engine is off, trans in gear, clutch in, then the input shaft and clutch disc are spinning which could create noise. This is also push type :)
@@TheCarPassionChannel Ah k cant speak for an push style throw out bearing here although it could still be a bad spigot bearing introducing reaonant vibrations as you put load into your gearbox/ drive shaft. Long shot but seeing as you've tried everything else its worth replacing next time your have the trans out, for a few dollars worth a shot if you have the opportunity
those driveshafts are supposed to have a center support normally although i know alot of people use 1 piece in e30s with getrags. could also be not having a rubber guibo on the output shaft mating to the driveshaft
2 piece driveshafts use a center support bearing, 1 piece systems do not. The Guibo is actually a possible solution to the problem, but may be difficult to pull off with a 1 piece shaft. That's something that's in the works.
TheCarPassionChannel Yeah that’s what I meant with the 2P system using the center support bearing I wonder how much vibration that takes out, assuming the vibration would be due to harmonic imbalance of rotation happening from the transmission through the driveshaft
I had a similar issue on a mustang one time and it ended up being both the rear rotors where warped. Also might want to get your rear axles checked. They could have got bent or slightly twisted causing them to be off balance.
My miata was making a noise that I could NOT find. Since I have an open diff I was able to get the rear wheels up to speed separately. It was really sketchy but I was able to pin point the noise to the driver side.
I’m really sorry about your issues with the Miata but, I’m really enjoying this content right now!
check the pilot bushing does the shaft reach it .
If you look at a cross section of the 260 gearbox you will see it has a different bearing setup on the output shaft compared to a gearbox with a slip yoke output shaft. The 260 was designed to use a center bearing on the tail shaft.
This is like a bass guitar that only buzzes on the 18th fret on the D string. Harmonics. Maybe. But I am hopeful this is a single component that is going to end up being located. Man you are a very methodical troubleshooter. This started after you put the bushings and the BMW transmission with the adapter kits if my memory is serving me.
I have the same vibration issue but on my s14 with a 1jz vvti and cd009 trans and z33 diff, I had my driveshaft rebalanced and it seemed to help a tiny bit but not really. The fastest I’ve gone in my car is 100 just because the vibrations feel so bad. I haven’t had time to try anything else. I do have solid bushings for the diff since it’s a conversion and my trans mount is polyurethane.
You're probably already looking into this, but I feel like a Guibo would solve this. Its meant to deal with driveline misalignment and vibrations in conjunction with the CSB.
That's a setup that KMiata and I are working on; the tricky part is figuring out a guibo setup using a 1 piece shaft since they have to have a zero degree operating angle. It's in the works though!
Try it without the drive shaft
Thanks for the video. Maybe good to check if your subframe is not bent, check if the diff is in line with the driveshaft and if your axle shafts are straight and true. Also your front bolts of the subframe brace to the car are missing as others mention, but I would not expect them to be the source of the issue.
Output shaft bushing (inside the tail housing)
I have has similar issues with wheels out of balance, a bad wheel bearing, and a bad tire. Also, an old issue that goes back to the NA Miatas - they like lower tire pressure. Dropping to 26 lbs can eliminate some highway vibrations.
Has the driveshaft been properly phased? Incorrect phasing of the u-joimt results in driveshaft vibration; a common issue on RWD front engine swaps.
Greg, there's a tip I learnt in school that might help you, grab some hose clamps that will fit around your driveshaft and tighten them on, see if it changes the vibration, moving them up and down the driveshaft as well as twisting them.
It could be possible that the driveshaft its self is balanced but possible slightly off centre when mounted?
What if it’s the bushings that you are using?
If we wait patiently Greg will show us what the issue is. Greg I just did some searching. There are some DIY tricks for balancing your driveshaft. But also shops that do it. I am fairly certain you have explored these avenues but just in case. You are spinning stock shafts very fast. How fast do you have your tires spun when you get them balanced? Curious....
I think the vibration is coming from your transmission crossmember bolted to your transmission tunnel need more rigid support plate
Is it down to unlucky harmonics. Length of driveshaft vs other factors.
Have you been able to check the gearbox out put and diff input shafts are parallel? If they're not it will vibrate! I work with this stuff on industrial equipment
They have a sensor kit where you can put them around the car and can locate the exact area of where the vibration is coming from
Sounds more expensive than jacking it up and hammering the gas lol! Not a bad option if this didn't work!
To be cheaper with it greg can go through with his knock sensor on megasquirt held at different positions along his driveline and view the direct sensor data to isolate the harmonic
Have you tried to put back the 6 speed and check driveshaft angles? Also might be that the Getrag is a little of center ti the diff. Its very strange, and I don't have any clue why the driveshaft have such severe vibration.
Thanks for keeping up the passion. Good troubleshooting methodology.
check geometry: gearbox output shaft must be parallel with diff input shaft, otherwise you can have variable angular speeds, The same applied to cv joints. This joints does not tolerate big angles
I thought you would shoot under the car, set cruise control at 80-100mph, and watch at various angles the drivetrain components and what could be harmonizing in such terrible fashion. Darn it Greg! Well, I can't wait to see what you've learned on the next one. Great videos buddy!
I'm not fond of being underneath a car on jackstands with the wheels in motion.
@@TheCarPassionChannel Yes, but cameras on all the components would make things visible.
Here a thought.... now what if the transmission mount is vibrating the hole car from the rpm speed of the drive shaft of was there to holed the Tran and diff but also was to stiffen the chassis what if that could be the problem more power bigger transmission bigger components more vibration I know the trans has a damper and so dus the drive shaft but what if it just the trans mount
7:30 there is a bar that is not bolted down left of the exhaust hanger, is it rattling against the chassis maybe?
Edit: just realized someone already pointed this out
dont have a clue here but from any car i ever worked on the drive shaft always had the slider part of the shaft mounted to the trans and the big part of the drive shaft mounted to the diff....which is not how its mounted here in this video
This might be ignorant of me but the bolts from the trans crossmember are laying directly on the trans with washers but wouldn't regardless metal doesn't isolatethe vibration. Wouldn't vibration move through the bolts into rest of the chassis?
I'm starting to suspect the transmission tunnel wasn't designed to dampen the high frequency vibrations of a high RPM driveline. Whatever the tiny BMW bushings don't absorb is possibly being transmitted through the body of the car. The PPF forced these vibrations to travel up and down the driveline all the way to the engine mounts and differential mounts. Now that vibration may be taking the path of least resistance straight into the center console? Perhaps some type of dampener or "weight" on the new transmission mount to absorb vibrations. I see these constantly on newer Chrysler built vehicles....on the body to frame bolts, on the exhaust, etc. Even seen them directly on the differential case.
sparks near the diff or flashing light from vibrations at 6:35 ?
i've seen that too, altough it is also happening at low rpm's aswell.
at 7:00. Bolted mounts on the side to something?. Cross member with rubber isolators. Are those two mounts equally loaded? Or, in other words, is one carrying more weight than the other?
Is there any heat in the brakes after trying the tests? A while ago I had bad vibrations which were caused by contact between pad and disc. New disc pads and service on calipers fixed the problem.
May or may not be an issue, the diff looks like its mounted from the PPF to the chassis with no bushings, I know your setup has delrin diff bushings but if the diff is still mounted solidly to the chassis in other places, it may cause vibration?... it's weird because driveline vibes are usually at low speeds
I’m thinking either the trans or the diff is off to the Left or the right slightly.
I think your piston return springs might be bad. Chrisfix made a nice video about those. :)
ChrisFix - April Fools 2019? Or 2018 I can't remember lol
Well I’m glad I changed from a 260 to a ZF 6-speed before this happened lol.. Good luck Greg, maybe the custom center support driveshaft can solve your issue.
have you actually look at the driveshafts. from diff to hubs?
He's tested multiple driveshafts
he’s shown he’s tested multiple propshafts. maybe i’ve missed it but i haven’t seen him testing driveshafts
@@bmxbarn15 you mean axles.. :)
no i mean driveshafts. from the diff to the wheels they’re called driveshafts
@@bmxbarn15 maybe from a technical standpoint, but the mass majority of the community calls the shaft from the trans to the diff a drive shaft, and from the diff to the hubs axles or axle shafts... at least in the states.
That was an awesome analytical approach. Great job. Its gotta be a rotating mass thing...somewhere. It sounds/looks like you have eliminated tires/wheels, engine-related, and driveline. That leaves transmission, diff, axle shafts, and associated mounting stuff. What a bugger! Best wishes. If its not some weirdo "harmonics" thing where two different things are affecting each other at a certain speed, I'm sticking with transmission.....
I wonder if it has anything to do with that trans mount just being thru bolted. Or maybe fabricating a ppf
It might be a diff issue. I just put in a torsen in mine with unknown mileage and I get pretty bad nvh noises around 75 80 mph. I'm thinking it might be a pinion to ring gear meshing issue but idk for sure. Granted it may be accentuated my using poly mount brushing but maybe try another diff? Maybe because the ppf isnt absorbing some of those vibrations anymore?
Have you tried the "stock BMW bushings" maybe that are too soft for a Miata application. Take a vid of the back of your transmission and the front of your differential and check for up and down, side to side movement.
I have same kind of issue.. It vibrates at 2700 rpm when you let the trottle of.. The driveshaft bearin has been replaced and the torsen diff has been shimmed.. Torsen cog wheel maby vibrates??
Try swapping those rubber transmission mount bushing for something hard, and see how that makes a difference. Like back on the jack stands and driving. The symptoms i would be predicting is slightly more vibration at low speed, and reduced vibration at high speed
Have you tried changing gearbox bushings/mounts for something with different stiffness? since vibrations are speed related, there should be something with that speed or frequency that causes it. And resonanting frequencies are determined by stiffness of elastic elements and damping. So I'd tried to replace all bushings with solid mounts at least temporary for testing.
and if it will not help - have a look on structural rigidity of places where components are mounted. Maybe those are acting as springs in your case...
Could it have something to do with the fact that the transmission cross member is solidly mounted to the transmission tunnel? Thinking back to how Miata drive train components are mounted stock, no drive train component is that directly mounted to body work like that. Especially body work that is so non-structural (as I don't believe the transmission tunnel is). My theory is that vibration you are seeing in the drive line behind the output shaft are not being dampened enough by the transmission mounts and because the metal the transmission cross member is bolted into is rather thin, its causing the flimsier body to resonate at high speeds.
Might be worth trying to switch to softer mounts or adding insulators between the transmission tunnel and the cross member.
Could the problem be from the cross-member bolted in the tunnel? If there is a bit of play there it must have some effect on the driveshaft?!
This is similar what happened to my moms car about a year ago, the driveshaft was misaligned by about half a degree and that was enough to shake the hell out of the it at 60-65mph in 5th gear. The actual issue wasnt the actual driveshaft, but the driveshaft mounting point against the diff because at some point the car bottomed out and bent it. I'm not an engineer or a mechanic or anything but that was what I understood to be the issue and he showed me, replaced it, and it went away.
Pretty sure this is a resonant frequency issue with the drive shaft, by adding in the adaptor plate you will changing the vibration characteristics of the whole driveline. There's a lot of NVH engineering behind OE systems so there needs to be some further refinement. Consider changing the length of drive shaft as increasing the damping/bushing is only really covering up the issue. There must be some NVH specialists out there who can solve this with some modal analysis.
That’s what I thought too. Either design. Damper in the adaptor like the noze pulley or get the assembled driveline balanced and had a pin to make it is always assembled the same way
I get a metal scraping noise from about 3100-3300 rpm only. Doesnt happen in neutral
Another good one is you can fix your phone to different parts of your gearbox and diff and log the accelerometer data with any of the free apps. The vibration at the source should be thr strongest and you will have actual data to compare various systems.
Wheel bearing? Try the same test but only one axle at a time see if its only one side. you just have to isolate the vibration. the 96m i had done the same things at 55-60 and again around 90-100. it had a bent rims for a long time bore i had it.i replaced the axles and had the drive shaft balanced. sold the car never found the issue. think iv watched every video for the last 5 years. hope you figure it out.
Hi Greg. I haven't watched the whole video yet, but before i forget... My dad had a vibration issue on his car over 70 MPH and after much research and getting tyres re-balanced etc it turned out to be the Spigot Rings for his alloy wheels were something like 0.5mm too small overall. I didn't believe that this could cause such a big problem but it did! Might be worth looking into.
Just got to the part where you remove the wheels so yeah, ignore that comment :D
Not sure if you tried yet or talked about yet but what about disconnecting the drive shaft from the trans and run the test in 5th again? That may rule out the trans.
Have you thought about adding a ppf power kit to see if that will help i seen it on moss miatas site
Would like to have seen a camera angle showing the rear of the transmission during vibration
I don't remember if you checked already, but what about the wheel bearing?
New
Hi Greg , I feel your pain. I think that the problem is related to where you put your supporting brackets for your gearbox. If it were me I would be mocking up the location of the geabox while supported on a jack with a lazer on a magnet or something at the back end. After 'clocking' the lazer for alignment - point the lazer at the centre of your diff and rotate the engine while adjusting the jack for good gearbox alignment. Thats the point at which to commit to putting holes in for your supporting brackets. I think your vibrations are related to an eccentic loading while your drive shaft is rotating. Theres no point in having a balanced drive shaft that isnt perfectly aligned. Happy to talk more about this... I'm used to be a cnc machinist and know the follies of having things that rotate fast that arent perfectly aligned and balanced
Couldn't you take the Axel's loose to check the diff? I have a 67 Chevy II. 350 350t trans and Ford 9 in rear end. It does the same thing vibrates at higher speeds. Almost positive it's somthing in the rear end. Haven't tore into it yet
This might be out of this world but if it’s possible I’d say try making an adapter for the driveshaft to the trans with bumpers inside to absorb vibrations. Something similar to what the bmw trans come with. Cause your drivetrain and engine are all stiff due to your bushings. Maybe if you have something in their to absorb more vibrations. Cause the CV joint probably only helps so much
This is how the factory BMW's (and many other cars) are set up. I may be going to a setup like that soon.
I dont know If checked already but i had an issue where the Break disc we're unbalanced. I got Vibration only in 4500+ RPM. May Check this
I did see where you just kinda threw the trans mount in it. Wasn't it supposed to be at the perfect angle?
Seems like you’ve tried quite a few s things with the driveshaft. I think the next step should be to experiment with different stiffness engine and transmission mounts. You should probably also try stiffer or softer diff mounts.
Hey Greg I don’t know if this could be it or not since you were saying there are others running this kit as well with no issue but when you look at how the trans bushings are setup technically since the bolt passing through is still sits both on the transmission and on the mount that is bolted to the body it still could be sending vibrations through it even with that bushing in the middle. Think about like the diff bushings and the motor mounts. The bushing completely isolates one part of the car where no metal is touching besides either the body or what is being mounted. Maybe try throwing some rubber on one side of those bolts to see if that might at least help a little bit
On the transmission bushings they are actually not through-bolts, it's a cylinder of rubber with a stud on each side, so they offer complete isolation :)
There are like two dozen comments saying its a wheel bearing or a cv axle, and *Greg literally says in this video* that they have been replaced. Good luck with your problem Greg. My money is on one of two issues: Two piece driveshaft, or trans internals. Dont forget the output shaft of the transmission is always spinning at driveshaft speed too, it could be trans internals (maybe some old bearings in the trans are allowing the output shaft to wobble in place?) either way, good luck with your gremlins dood
Can't win em all 😂 I've actually got a buddy with the same setup, and the same issue, he bought a built G260, all new bearings, and it didn't fix anything. So lucky for me, I didn't try a built box haha. Definitely heavily leaning towards driveshaft harmonics or something of the sort.
Did you test the connection of the trans to the car? The Bracket, the bushings, the chassis contact points? I mean the trans will vibrate and the miata structure is not engineered to take these loads at those (new) contact points.
Great vids, keep em coming!
A tuned helmholtz resonator is used to eliminate a specific drone frequency. What is the equivalent for vibration frequency? Adding weight to a specific area? OEM's have NVH labs for this stuff and crazy smart people with PHD's in this. Not fair lolol. Goodluck man
Has the slip yoke engagement been investigated? To far pulled out would be bad at speed, just the tolerances within the slip splines could cause the shaft to come out of true.
In Sweden we have a saying "Trägen vinner".. which is from the north where people barely speaks (hence the shortness).. means "Stubborness wins".. just keep at it, it will show itself eventually!
This brings me back to working on minitrucks
You can always look into investing in some chassis ears they pick up sounds and vibrations and can be mounted anywhere by zip ties. Same stuff we us at my work to find noises or vibrations 👍
Is there such things as chassis ears that you can place them on moving driveline parts
If you find the wireless ones just make sure they are really secured