How a Differential Works | Trucking Smart
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- เผยแพร่เมื่อ 2 มี.ค. 2017
- Learn how a differential works on a car, semi-truck, or bus. And how to use the differential lock - watch the video! SUBSCRIBE TODAY! ► / smartdrivetest
The differential axle is the rear axle of a rear-wheel drive vehicle. The differential allows the rear tires to spin at different speeds. When a vehicle goes around a corner, the inside wheel slows down and the outside wheel speeds up. In other words, the two wheels on the axles must turn at different speeds. The differential axle allows the wheels to spin at different speeds and still allow the power to be delivered to the rear axle.
For a more detailed explanation of the differeential see:
Around The Corner (1937) How Differential Steering Works - • Around The Corner - Ho...
David Leifheit inadvertently left the differential lock ON and drove the vehicle at highway speed. He wanted to know if this oversight would cause hub bolts to break. It is unlikely that leaving the inter-axle differential lock and driving at highway speeds would cause damage to the axle - especially if it was a one-off...in other words it only happened once.
When engaging the differential lock on a unit, it is advised to do it at slow speeds when the vehicle is travelling in a straight line. NEVER engage the differential lock when the wheels are spinning.
On muscle cars and 1/4 mile dragster, the vehicle is often fitted with a posi-traction rear-end that allows both wheels to turn at the same speed. By forcing both wheels to turn at the same speed, the vehicle will accelerate more quickly.
On some Western Star trucks there is a differential lock on both rear axles. As well, the truck is equipped with an inter-axle differential lock; therefore, all eight tires on the rear of the truck are locked and turn at the same speed. Most trucks only have a differential lock on the front axle and thus this is why it is recommended that winter chains are fitted to the front of a tandem axle.
Differentials are fitted with worm and spider gears.
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no but had problems with diff lock leaking and not engaging and had to wait in the morning for a big farm tractor to pull me over the jump up (88.2 ton gross pocket road train )not my fault the truck had severe use in hilly terrain and our 4x4 bush fire truck blew a diff cause of something electric over air failed
Hi sensai cobra - Apologies for the late response. Thank you for your comment. And I too have had issues with those electric over air controls. Mine was in a bus that shifted the transmission. Are you in Australia that you're pulling road trains? All the best my friend, Cheers Rick
I broke the driveline between the axles as I pulling out of the bottom of the rock quary. I rolled my truck up against a giant rock and removed the driveline. I then engaged the inter-axle differential lock do that all the power would go to the front drive axle and drove it 60 miles like that. Definitely saved getting hauled with a tow truck. Front wheel drive also has a differential. Thanks for the video
Have left on, just dragged the tyres a bit. Great video as well. Thank you.
Hi jfsa380 - thanks for your comment and the great information - that really helps out those that are coming into the industry. All the best, Cheers Rick
Thank you for these informative videos, they really help!
Hi ThatCampingOwl - Apologies for the late response. Thank you for your comment. And you are most welcome. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Excellent Video for beginner Thanks
Hi ravinder kumar kakkar - Thank you for your comment. And you are most welcome. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Thanks
Hi atarukoh - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick
Thanks for the video
Great presentation. Thank you!
Hi Robert Smith - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick
This (and comments) is all really good info. I l once left diff lock on between stops at freeway speeds, only a few miles away. Just did it again yesterday, and while I feel really stupid for having done so I'm glad it seems to hopefully not be too terrible. Agree that there should be a little buzzer reminder or something.
Some days it's challenging to be human my friend. It's not a huge issue. Safe trucking. All the best, Cheers Rick
Awesome info , THANKS
Hi Erik Dell - Thank you for your comment. And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Always great information
yes once and it did no damage because I caught it a couple hundred miles down the road, turned them off once again didn't have to make a lot of turns. This is an excellent presentation.
Hi Ladonna - YT comments are odd because I was certain that I replied to your comment?? That is great information for the other drivers coming into the industry. I'm wondering if the vehicle manufacturers should put a light or a beeper on the diff lock - I guess if there was a chance of damaging the vehicle they would. All good though - thanks again, Cheers Rick
Rick I commented then watched then commented again.....mean time others were commenting and it seperated the comments...lol! Sorry bout that!!! Have a great day!!!
@smartdrivetest Freightliner’s typically don’t have a buzzer for the diff lock, but they do for the suspension dump. Volvo’s have a sensor on everything they could possibly throw a sensor on and it does give you a message in the driver’s display that the diff lock is engaged if you go over a certain speed. I’ve had more sensor issues with Volvos and there not be an actual problem than any other truck I’ve driven.
Great job on the video👍🏻
You make a great couple!!! Good luck!!!!!!!
im taking a driver pump operator class and was wondering does the differential lock work the same on fire engines/ladder trucks?
We had a new driver engage the Differential somehow either one or both axles and ended up needing a tow afterwards. His reasoning for even using it was because his friend told him that it would make him go faster. He's no longer an employee.
Hi Cory - did he need a tow because something broke or he got the truck stuck? Cheers Rick
@@smartdrivetest Something blew when the driver did that. So i'm unsure of what exactly but it wasn't pretty lol
Part of the issue with new drivers is that they’re often not trained about these things and are left to figure it out for themselves. I’d also suspect there might be something wrong with the truck. A different lock really has to be abused to do damage to the truck. Cheers Rick
thanks sir
Perhaps sir, you could do a video on drive axles and final drive ratios. Pro's and con's. TH-cam lacks these videos. Thank- you.
I'll have to see what I can do my friend. That information is a little beyond my expertise. All the best, Cheers Rick
Awesome Video!🎥
Thanks!🤗
Hi Valerii - thank you. Are you getting spring yet? We are beginning to warm up here, but it is slow. All the best, Cheers Rick
I left the diff lock on for over 2,340 miles vale nc after getting stuck on my way to LA ( indicator light was burned out) and i just had the diff serviced and ran the truck another 340,000 miles with no issues. Got a new truck and that one was still going strong.
Then I had a codriver run an interlock for 10hours at speeds up to 75mph and never had a problem. Truck has 650,000miles on it now
Hi Rodney Long - apologies for the late response. Thank you for your comment. And thank you for that information. Yes, unless you are dong a lot of off-road stuff, I don't think the diff lock is going to do damage. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Lmao
Can I add one locking differential to only one axle. On Volvo 2006 670? Could really help me in deep snow conditions. Already able to lock the two drive axles together.
Dennis
Great video!
Hi adam-david Vaught - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick
Terrific. Thx
Hi MrDave 777 - you are most welcome my friend. All the best, Cheers Rick
AWESOME AWESOME AWESOME!!!
Thanks Ladonna!
Front wheel drive vehicles also have differentials in the transaxle
Hi 33CVU - Thank you for your comment and correct information. Yes, what I meant to say in the video is that front wheel drives do NOT have a differential the same as a conventional differential in a rear axle. All the best, Cheers Rick
On semi truck which tire creat power only one from one side or two front axle.??
nice sir 👍 I'm always watching the full video keep up the good work my new friend.
Hi Remar Mechanic - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick
when you have the diff on you only drive stright. of you turn to left or right like down on a road, you risk to broke the axel becorse you inner wheel drive more slow then you outer wheek, sp dpn't do that stunt.use only diff luck when you can not get out, and as soon you have to turn you stering whells like for left or right, then get it out of diff luck again, if you drive on asfalt with load on, you can almost not turn you sering whells, becorse you back axel try to drive stright.. so get it out of diff luck as fast as you can again,, diff lock is only for emerginsy when you get stuck in the Mud.
Both my locks have a terrible high sounding alarm. I guess that helps.
I drive an 05 peterbilt 379 what Alex would normally be the mean movers?
Hi El wray - Thank you for your comment and query. Normally it would be the front axle, but if it's a vocational truck, it may be the rear axle, although most likely the front one. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
What about my kw w990 2021 the switch is off and on the dash it's telling me that I have the switch on and I don't no if it's locked in or not
i'm planning on build a custom welding truck and i was think of making it a tandem axle truck, is the gearing different in the axles or is it the same gear ratio in both axles. i know for a small time personal welding rig i shouldn't need a tandem axle rig, but i want it for weight distribution on the bed. without having to get a CDL
Hi David - thank you for your comment. I would suggest that you stick with a single axle vehicle. A tandem axle vehicle gets significantly less fuel economy than a single axle. A mate of mine suggested that you think about a Ford 550 or 650 for your rig. If you do go with a tandem, yes, the gearing in the axles in the same. And, I don't know where you are, but here in British Columbia, a 3 axle vehicle requires a Class #3 license. Those are some other factors to consider. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
thanks for the info, im in the usa
Which state are you in David - I'll look up the requirements for a 3 axle vehicle for you?
Max before a CDL is required is 26k pounds, once it exceeds that gross weight you will be getting into CDL territory. Also if you plan to tow a trailer you are good for 16k tow vehicle max weight with 10k of trailer weight, and again anything over that in combination will require a CDL, if it has airbrakes then you need to obtain the airbrake endorsement and is a standard requirement for CDL.
Do both the rear axles receive power when the interaxle diff lock is not engaged, or is it just the forward rear axle? In that case the back rear axle would merely function as a dummy axle until the interaxle diff lock is engaged. Correct?
Hi D Majumdar - Thank you for your question. Yes, unless you have an inter-axle lock, it's across the front-rear axle. It may vary from across brands of truck too as to which wheels receive power. Few trucks have both a diff lock and an inter-axle lock. All the best, Cheers Rick
@@smartdrivetest thanks for the reply!
You are most welcome. Cheers Rick
If you are turning sharp with diff lock in and at high speeds especially of course the axles will come under stress because they cant move at different speeds. So yes it will break hub bolts and have seen damage multiple times because of leaving diff lock in.
Hi Bailey Smith - Thank you for your information. It helps out other smart drivers my friend. All the best, Cheers Rick
Great Info. My question is, in normal conditions on highway which wheel has drive or all 4 has drive or X drive..?
thanks
Good morning Andrew.
In normal operating conditions, with the power divider unlocked, torque, or power, is going to flow equally to the front and rear drive axles.
This is where things get tricky, because this would lead you to believe that all four sets of duals should receive power. However, in the unlocked condition, power is sent to all four SO LONG AS TRACTION IS EQUAL.
However, when one axle encounters poor traction, 100 % of torque flows to that axle, and through its differential to the wheels with the least traction.
On the vehicle, this results in one set of wheels on the front or rear axle spinning out.
When the interaxle lock, or power divider, is locked, torque is now distributed equally between the front and rear axle independent of traction; the front and rear differentials are mechanically locked together. In this condition, each axle will still send power to the wheel with the least traction, which can result in the “x” pattern you described- the right rear and front left spinning out, or vice versa. It is possible though for both left or both right to spin out, if both duals on each axle have poor traction.
This is where a differential lock comes in, forcing both sides to pull regardless of traction.
In short, with the power divider unlocked, power flows to all four corners equally so long as traction is equal.
With the power divider locked, power flows equally to the front and rear axles, independent of traction; each will receive 50% of the engine’s power.
I hope this helps!
If driving approximately 45-50 mph on relatively flat highway in snow, would it be advisable to use the locking differentials?
Hi Pamela B - Apologies for the late response. Thank you for your comment and query. And no, I wouldn't recommend using the diff lock. It is a feature that is designed to be used a low speeds. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Thank you 😊
Hi Pamela B - you are most welcome my friend. All the best, Cheers Rick
I agree with Rick, the power divider and axle lock (if equipped) are great traction aids when needed, but keep this in mind as well for when you do need them. If your tractor is equipped with BOTH a power divider and axle /differential locks, steering can be affected if the steer axle tires are on a slick surface as well; snow and ice, or mud.
With one or both rear axles locked, the truck will resist turning and want to “push” straight ahead even with the wheels turned. This can sometimes catch a driver off guard in tight quarters. Rick did mention it’s best to use them while traveling in a straight line because it does put less stress on the drivetrain as well.
We must remember that when ever you lock a differential it can over power the steering. For example if you try turning in a mud pit with your diff locked you might find the truck wanting to PUSH or SLEDGE. This is made worse at higher speeds and can be really dangerous. I was advised by some old timers to turn the locker off over 40kmh, it shouldn't be needed at speeds above that. Just my 2cents, hope this helps
When damage can be caused if u ingage while in motion
So.. ?
Just a question...Which Differential drives the truck the front one or the Rear one?
Hi Jay Jay Mr. Canada - Thank you for your comment and query. Most of the time, it's the front differential that drives the truck while it's going up and down the road. That's the reason for putting the chains on the front-most axle when chaining up, unless you have an inter-axle lock and then it doesn't matter. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Jay Jay Mr. Canad
check your drive tires usually its the front drives wear the quickest and using Jacobs engine brakes wear all your drive tires out a lot quicker too
its actually both differentials, the tire uneven wear is due to turning
@@smartdrivetest wrong
@Smart Drive Test I have a question . Under slippery conditions, keep the inter- axle differential unlocked to get more traction ? True or False I say my answer is false you would want it locked in slippery conditions Yes I'm going to school at NTTS here in Buffalo N.Y. we are currently closed due to the Coronavirus I'm still studying my books on my own Thank you for you time and cooperation
Hi there, in my experience your 'locking' applications will depend on your situation. Here in NZ we get it all- ice, snow, mud, holes etc etc. If you have a dual drive tractor and are experiencing 'slip' i personally will judge whether I go straight to diff lock or start with an inter-axle lock(if fitted). In un-even terrain situations I'll apply INTER-AXLE lock first allowing use of BOTH differentials. This does not lock the differentials (hub to hub) but allows to be using both differentials. Now if your experiencing 'slipping' due to mud, snow, ice etc then that's where DIFFERENTIAL LOCK should be applied. I would STOP, apply brakes, apply lock to FIRST diff then gently apply acceleration- gently allows the gears to mesh together smoothly and reduce wear on the internal components. If you still have slip, then repeat the process for the rear differential- this in most cases will allow you to move forward or reverse out of MOST BUT NOT ALL situations. Once you have regained traction and it's possible to stop or are moving slowly disengage the lockers and inter axle lock and resume your day. Hope this helps.
Left diff lock on 2020 new Freighter Cascadia often & at 70k miles it stopped working blowing air inside axle housing not engaging buy losing air pressure. Opps! Not fixed yet but still drives
Good to hear that it didn't stop the truck. Probably best to get it fixed sooner than later. All the best, Cheers Rick
Unknowingly (issues with lock mechanisms) i drove my truck with differential on for way long time with lots of turning until when drive shaft in between axles broke. At the mechanics it was found the mechanism was indicating the diff. is off but actually engaged. Gears where inspected no damage found. At least that is my experience with diff. locks........
Hi Christopher Zablon - Thank you for your comment and information. Most of the time, leaving the diff lock on isn't going to do damage, but it will after a period of time. All the best, Cheers Rick
@@smartdrivetest You're absolutely right Sir, it was a big scare!. What happened to me may not produce same results to other drivers (bottom line is stick with recommended Diff. guidelines), I'm more attentive to what's going on with my differentials now than ever before.
@@christopherzablon8336 it would be interesting to know the torque loads through the half shafts when running the diff as standard and with diff locks on. Im guessing the torque load increases significantly on the half shaft when it is locked and trying to turn at a speed it isnt meant to be doing with the increased load been exerted on this part. I assume this is why there is a speed limit and distance set on the differential locks been engaged as the increased torque (if this is what happens) makes the half shaft the weak point in the running gear. I really am just guessing out of interest but it would be interesting to understand the subject further and if this is the reason why it is suggested not to be done. I could see those running diff locks on highways having no issues as the wheels are running true with each other and under less torque stress as the vehicle rolls at speed, im sure multiple tight bends at higher speeds than suggested is when the real damage starts to take hold.
@@Dieseldogmodels The main issue I could see with running with the locks engaged especially at highway speeds is this: depending on varying amounts of wear on the different tires on each axle, you could end up with very minor variations in tread depths. This would lead to minor variations in circumference at the road which would cause the tires to spin at different speeds. At low speeds this would only result in a minor amount of tire scrubbing but could put tension on the axles and half shafts at highway speeds because small differences would get magnified with a larger total speed. This could either cause more scrubbing or more torque loads or both neither of which is good.
I had a strange situation where I was completely out of traction because of the irregular terrain. Essentially One wheel set on the rear axle was up in the air because the ground sloped down severely and on the front axle the opposite tire was down in a bit of a Sandy rut which meant that tire was just spinning in place with no forward motion of the vehicle. I essentially ran out of traction and I had the interaxle differential lock engaged. Had I had at least the ability to lock one differential completely I would of been able to drive out but I had to be pulled out with a chain
It happens to the best of us my friend. Great story and learning experience. All the best, Cheers Rick
Good morning! It’s very frustrating flexing out the tandems and having perfectly good rubber just out of contact with the ground!
Here’s a trick that can get you out of that situation SOMETIMES. I stress sometimes.
If moving forward (or reverse) slightly will get you on good footing, and not into more trouble, lock your power divider and put the truck in the lowest available gear. Idle off the clutch, and allow the wheels to spin slowly, at idle speed only.
Apply light and gentle brake pressure. The idea is to slow the spinning wheels and bias torque to the wheels with good traction, forcing them to pull. You are essentially tricking the differentials into thinking there is equal traction on each axle.
That being said, if the truck hops, bucks, or does not begin to move, push in the clutch, and stop immediately.
Continuing to try to power out can cause drivetrain damage to the truck, or get you spun down and into a worse situation than you were in.
I have problem,when I am driving burning oil and mechanic couldn’t understand please explain thanks
You're burning oil in the differential? Is it a car or a semi-truck? All the best, Cheers Rick
If I disengage the diff while moving; will it cause damage ??
Hi Lorenzo Pacheco - Thank you for your comment and query. If you have the vehicle in a straight line and less than 10mph (15kph), it's not going to do any damage to the differentials. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Smart Drive Test thank you! Just got a job driving end dumps and bellies this will be helpful
Hi Lorenzo Pacheco - Thank you for your reply. That's awesome - so you're doing a lot of off road stuff? What are you hauling? If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Smart Drive Test I’ll be hauling rock, asphalt, fill dirt from pits and they have some rough terrain. Thanks! Sure will.
Hi Lorenzo Pacheco - Thank you for your comment. That's brilliant. When dumping end dumps, make sure you're on level ground, and that the grounds solid. And always look up for overhead obstructions. We had a guy at one of the companies, they were hauling wet clay, and it stuck in the front of the box. When he raised the dump, it wouldn't let go and of course the load wasn't balanced and the whole truck flopped over. The worst part was that it punctured the fuel tanks and then the trucking company was charged with an environmental spill. When in doubt - ask questions and you'll do great. All the best my friend, Cheers Rick
I'm new to trucks, my brother left me a ten wheel dump truck, l got it parked on a soft surface in the rain and it continues to rain for two days. One tyre on each of the rear axles are soft and it will not move,only one set of wheels on each axle are spinning. Any answers?
Hi Howard Darlington - hook a chain on it and give it a tug my friend. Despite the myths, big trucks are terrible in the mud and in the snow. You either have to put chains on the tires or give it a pull. It won't take much - you can probably pull it out with a pickup truck. All the best, Cheers Rick
How do you safely disengage the diff lock?
Hi Rob Mart - Thank you for your comment and query. To turn off the diff lock, you slow the vehicle to less than 5mph or come to complete stop, turn it off and then resume. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
@@smartdrivetest I thought maybe you would have to back up a bit to release the tension. Thank you for your response.
Hi Rob Mart - you are most welcome my friend. All the best, Cheers Rick
I'm buying a kenworth T660 with a 10 speed manual. I would like to run between 1400-1500 RPM at 75mph. I can't seem to find info for this. 3.25, 3.55, etc. What would be best? P.S. I'm running dry van
Hi Daniel Nelson - Thank you for your comment and query. I'm not a 100% certain, but I believe the best rear to run highway with a dry van is 390 rears. And the people that would be best qualified to help you set up the truck are the dealership. They'll be able to tell you what rear-end you need to put in your vehicle to set it up properly with both the engine and transmission that it's currently set up with. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
You need to know tire circumference and transmission gear ratio to figure this out
front wheel drive cars have differentials too built into the transmission
Hi MASTER MECHANIC Felipe - Thank you for that information. Smart drivers helping smart drivers makes us all smarter. All the best, Cheers Rick
Is the differential built into the transmission or transaxle?
My truck has problem when I turn differential switch on I hear air does something but only one rear wheel spinning on passenger side. What can be the problem? What's need be checked or replaced?
Good morning, Johny.
This is a year late, but if you’re still having this problem, hopefully this will help you out.
You mentioned hearing air when you toggle the switch; if you only hear this when the switch is flipped to lock, I would verify the switch valve body is good, and not leaking (bypassing) air to the exhaust port. Normally, in a functioning switch, this is where the air pressure in the signal line would be exhausted to atmosphere when the switch is toggled to the unlock position.
If the switch is functioning correctly, check for leaks in the signal line next. This line is pressurized when the power divider switch is in the locked position, and sends air to your forward rear axle. Listen for leaks in this line. Run the engine to build air, then shut the truck off, and engage the switch. Turn the key on while doing this, so that if you are losing air, the low air alarm will sound and alert you ( nothing is more aggravating than chasing an air leak with no leaking air 😂)
Doing this will also give you an indication of the severity of the air leak. Also, a bottle of soapy water will help you to find leaking unions or pin holes in lines.
If you follow this signal line to the differential, and have not found a leak or defective component, the problem may be the actuator in the power divider unit.
Some trucks use a diaphragm actuator and linkage that will resemble a brake chamber, and some use an internal piston. Either of these components could be leaking or stuck /binding.
If this is the faulty component, you may want to consult a shop for repairs, depending on your mechanical ability. It is possible to do further troubleshooting to confirm the actuator, but I wouldn’t want to put you in a position where you may inadvertently lock the differential in the locked position, making your problem worse than just a non-operational power divider.
I hope this helps, and if you’ve had the problem addressed, hopefully it will at least give you an idea of how the system works, and can maybe save you some money down the road! Good luck, and best wishes.
Common misconception an interaxle differential lock does not lock all wheels together!
the power divider sends 50% to the front differential and 50% to the rear differential, it does not lock the front differential like you said.
Hi MASTER MECHANIC Felipe - Thank you for your comment. Are you saying that there's a difference between a power divider and a differential lock? All the best, Cheers Rick
@@smartdrivetest correct. The divider on Class 8 trucks divides the power between the front most and rear most axle. Not all trucks have dual driven rears, which is why they say to put the chains on the front most axle. The power divider distributes the tractive effort between both axles and reduces the need for a locking differential in most cases. (This is why they don't want you to engage it during wheelspin, you have one axle dead stopped, and your driveline moving, you'll put a massive shock into the system and damage the divider) Most trucks do not have locking differentials but may have a power divider instead. That's why you'll see many trucks stuck because the driver didn't chain up. They thought their differentials lock up and in most cases they do not. They also recommend that you do not run highway speeds with your divider locked for the same reason why you shouldn't drive highway speeds with a locked axle. The difference in speed from the rearmost axle to the front most axle varies enough to cause binding and can damage the divider or cause a dangerous situation when loss of traction occurs at higher speeds.
@@EyebrowsMahoney What you say here is correct, but there's a bit of a nomenclature problem. All tandem axle trucks (trucks with twin rear drive axles) have a power divider. They MUST have one. That's because a power divider IS a differential, allowing differentiation between two axles instead of between right and left wheels. Most power dividers can be locked (cancelling differential action and causing the drive inputs of both axles to rotate at identical speeds), but I've heard there are some that cannot be locked, so they always function as an inter-axle differential. You can't run twin driving axles without a differential between them for the same reason that you are saying you can't run a power divider locked at high speed. There will always be the need for one axle to spin a little faster than the other due to tiny differences in tire size, inflation pressure, etc., and if one axle is "trying" to turn at a slightly different speed than the other, huge torque loads build up within each axle and within the drive system that connects them together, and at higher speeds, that torque build-up tends to be greater.
www.desitrucking.com/understand-your-power-divider/
If the difference in speed that each axle "wants" to go when the drive line locks them together is great enough, drive-line parts tend to break. I heard of a heavy-duty all-wheel drive truck (used in potato farming) which had the front axle geared to spin significantly faster than the rear axles as a compromise between what's needed for sharp turns and what's needed for straight-ahead driving. The front axle must spin faster during sharp turns, so gearing it to at least spin a little faster than the rear axles helps the truck make sharper turns off road than it could do if the front and rear drive wheels rotated at the same speed. Gearing the front axle this way is acceptable in off-road applications, but if the front axle is left engaged for on-pavement use, an axle shaft will shatter within a moment of getting onto the pavement! Because the differences in speed that a pair of identical drive axles "want" to spin is minor, leaving the twin axles locked together won't result in the kind of catastrophic damage as was the case for that heavy-duty off-road truck I described, but it does constitute abuse and damage will accumulate over time.
Having the power sent 50/50 is the definition of what a locker will do. A diferential allows the majority of the power will go to the wheel/tire with the lowest amount of traction
@@EyebrowsMahoney I have a question on my Mack truck I got stuck and put the lock in. So now the truck does not move. The trans runs but when it turn in the differential it does not run Unless the rear differential is Locke then it move but low speeds. What can be the problem for the from one to not move a broken pin? There’s no noise when moving
what if different lock pops when you try to move it straight.
Hi Brian Helm - Thank you for your comment and query.If the diff lock pops out, there may be something wrong with the truck. OR there's a possibility that you don't have it completely engaged. Try those 2 things and let me know. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
What if you engage the diff lock and nothing happens can it be the switches
Hi Ash A. Depending on your truck’s make and model, it can be several things that need troubleshooting.
Before digging in, what has led you to believe nothing happened? I don’t mean anything by that, other than were you stuck at the time and needed the traction aid, but it wasn’t working? Or did you push the lever / switch and didn’t hear anything? What were the weather conditions at the time? Unfortunately, if yours is air operated, the systems do not get used regularly, and moisture can freeze in the lines and prevent them from working- WHEN YOU NEED THEM THE MOST! Did any indicator lights come on in the instrument panel?
If you were sitting still, and just turning it on to become familiar with the controls, chances are nothing will happen- other than a small spit of air ( like flipping the range selector on the shift knob), if your truck is old enough for the switch to be air operated.
Chances are that the switch is electric though, again depending on the make and model of your truck. If so, and no indicator lights came on, including a light on the switch, I’d check the operator’s manual (if you have it) for a fuse location in the fuse box.
If it is an electric switch, and the fuse is good, then power and ground will have to be checked at the switch to verify the harness integrity and switch function. If this doesn’t solve the problem, a technician will most likely have to verify the harness integrity between the switch and axle(s), and the actuators themselves.
If the switches and power divider / axle locks are air operated, the supply air, switch, and switched air will have to be verified, and if that checks out ok, the air lines and actuators will have to be verified.
I hope this helps, and hopefully it’s something simple :)
is it necessary to engage your differential when climbing and going down a steep grade
Hi Shaka Lee - Apologies for the late response. Thank you for your comment and query. No, you don't engage the the differential locks for those conditions, only when the ground is slippery or uneven. You might engage these if the grade is really steep - like you hauling logs in the mountains or whatnot. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Only use it when you feel like the conditions are difficult traction wise. We sometimes will engage everything when dropping down steep hills, heavy, and conditions are slippery. This allows engine braking to be applied to all 4 hubs. Not often we need to but it happens. In snow or ice we'll use the inter axle lock to have use of the rear differential too
Damage becomes when the speed exceeds 80 per hour. Nitrol should be used when unlocking the lock
Hi Emad GTR - Thank you for your comment and information. Yes, high speeds can damage the differential. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
@ Smart Drive Test
I have a Scania Series 3 11M360 1994
When I jack up my read left tyres the won’t spin I trie spinning them with hand they won’t go. When I turn my diff lock on it engages it works I turn it back off I can hear the air go and it’s off also on the switch the light stays on and on the display dash board it’s glowing saying it’s on don’t know what’s wrong!!? Anyone haw a clue thx
Also I bought a new switch same thing some say it’s not disengaging fully like my cross lock turns of but like my diff lock stays on
i believe that caused the damage and shear some bolts .
Yes but only because one of to rear ends had been replaced and was not to same gear ratio as the other rear end. Other than that their shouldn’t be a problem.
Differential function
I locked differential in my truck once. Unlocked them when was ready to go on highway but apparently it did not unlock mechanically.. so after driving around 150 miles on highway, stopped on rest area I heard bobling noise rear of the truck.. my differential oil was boiling. Next day it unlocked somehow, I changed diff.oil and still drove it for another year with no issues. Then sold it..
Hi Vitaliy Melnychuk - Thank you for your comment and information. I'd never heard about the differential getting that hot. However, if you're doing city driving and a lot of turns that would make sense. Good to hear there weren't any issues beyond changing the fluid. All the best, Cheers Rick
If that ever happens again, driving in a slight curve, forward and then backward, will, at some point in the process, release all the built-up torque between the two sides of the differential. It should be able to unlock at that moment. A similar trick is often needed to disengage the front drive system of an all-wheel drive truck. Also, I have a pickup with a "Gov-Lock" differential, and sometimes if it automatically engages harshly, it won't disengage unless I release the torque between right and left sides via the trick I mentioned at the beginning of this post.
Why would you leave it o in the first place? It would be like leaving a 4X4 with the 4WD engaged. It can damage things.
Hi Kevin - I'm know for a fact that he didn't leave it on intentionally. The newer trucks have a beeper that reminds you that it is engaged - a little bit like the blinkers on motorcycles. Cheers Rick
Front Wheel drive does not has a differential. Did I listen well?
Hi Luiz Gustavo Padilha - Thank you for your comment and query. You do have a differential on the front. It's just not the same setup as a rear differential axle. Owing to the steering, it's a bit more complicated than a rear axle. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Hi OttovonEarth - Thank you for your comment. What I should have said is that the front does have a differential, but it's not a conventional differential like the one on a rear axle. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick
Hi OttovonEarth - Apologies for the late response. Thank you for your response and great information. Yes, there are different setups on vehicles to work with the different wheel speeds when the vehicle is turning. And 76,000kg (167,551lbs) is really heavy my friend. Do you have driveline retarders or engine brakes to assist with downhill braking? All the best, Cheers Rick
Hi OttovonEarth - Thank you for your response. Yes, automotive technology has made great advances in the last couple of decades. I'm all for advances in technology. Take care my friend. All the best, Cheers Rick
I think I'm not the only one that came to see this video because we screwed up and left the inner axle differential lock on, I drove for an hour and a half going 70 miles per hour on a Freightliner Columbia before I stopped and took it off needless to say. Seems to be working fine but I did get s*** scared 😂
im loking nomber deperinsial
Have a Smart driver who broke the inter Axle is it because he had it on on the road..
Hi Sonia Barrera - Thank you for your query. If you wanted to send my the files, I would be happy to have a look for you. Always happy to help. All the best, Cheers Rick
The trucking industry is in crisis now for a reason!! After you do your math you realize abuse is taking place & there’s nothing you can do. Be smart stay there for a few years $ then quit. Don’t let the system ruin your life!!! Abrazo paisano!!!!