Thank you for what I believe is the MOST THOROUGH, TECHNICAL center differential/viscous coupling repair video available as of December 2023!!!! This will help A LOT!! 👍
I had the same issue on my Subaru Impreza 2016 (Sport Hatchback 5 speed manual transmission). I could not afford the labor prices the dealership asked. Also, it took me a while to figure out that it was indeed the center slip differential that was causing the clicking and clacking when turning at slow speeds, after the transmission came to temperature . I eventually diagnosed it myself watching YT videos. I'm not, by any means, a mechanically inclined person ( basic stuff only but I'd venture to try more complicated things with some help). Tried a couple of "mechanics" and they all misdiagnosed it as "bad CV Axle or wheel bearing". I can't do these repairs myself so I went and spent $650 for a new differential and had a friend/mechanic that put it in for me. It was a HUGE deal in terms of I paid in the end ! This video however got me interested in trying to re-build the old differential which I still have. My question is ... can these things be re-built indefinitely or is there a point where they're just "'done" and a new part needs to be purchased? I ran the car with the clicks and clacks (bad differential) for about a year (took me a few months alone to diagnose it). The old part looks perfect. Intact as far as I can tell. The part number that fit my car is "38913AA102". I also remember that during the process of diagnosing my issue and researching online for weeks, there was a mention of these units as being "sealed" which basically meant "swap the old part with a new one". Perhaps a marketing ploy ... I had no experience with this and "re-building it" was absolutely not even an option I considered but the differential in this video looks exactly like the part that fit my Subaru! Identical! Any help on this is appreciated it! And thank you for making such video! My utmost respect for your effort and expertise! Just a note (I notice it at the end of the video) -- the retaining ring which holds that back-cover which holds all the inner plates together, is not the same as mine. Mine is basically just a "retainer ring" that has two holes, perhaps for use of a retainer ring pliers. I wonder though, once that comes off which I think it should, everything else inside is the same?
Thank you so much for developing this rebuild. My viscous (38434AA021) is discontinued and very very hard to find a replacement for. I've just completed it on my 1995 WRX STI (used 100k fluid) and can confirm it's working great. I want to add that the older Phase 1 units like mine are rebuild-able using this same process. They are unfortunately welded shut and required machinist work to cut open and reweld after. If anyone has a phase 1 unit like me, I've outlined the rebuild with pictures at thesubaruforums.
hey, thanks for the updated video on this. I really appreciated your first 3 videos that you made, and also the additional updated info that you put in this one. I do have some criticism for you though. You seem very "rushed" and impatient in the video and you tend to skip forward in the video. I understand that you might not feel the need to show every thing because you have done this procedure a couple times now, but one thing to keep in mind is that there are people watching that have not, and might not even be close to having the knowledge and experience that you do. Leaving the original footage as complete as possible would be very helpful to people watching. Take your time, If that means splitting up the full video into multiple parts, then do that instead of kind of rushing through everything. Personally I think your original 3 videos were much much better than this updated one because they covered quite a lot more of the process and did not skip over steps like you do in this video. I would encourage you to redo the video again, and maybe put together a loose script for yourself to follow so that you dont sound kind of "lost" and frantic at times. It would also be very valuable for people if you did a video (series?) covering the job from the very start to the finish, I mean the entire job from the very beginning (jacking up the car, drive shaft removal, transfer case removal), all the way to the very end (putting everything back together and cleaning up). yeah I know, it would be a ton of work, but it would be worth it. it would be super helpful to people and would be something that you would never have to come back and redo or think about it again. anyways, thank you for your efforts with the videos. This video is nice as an update, but feels unfinished and imcomplete when compared to your original videos, I personally think those were more detailed and did a much better job at explaining what you were doing and why you were doing it.
Hello. Thanks for the tips. I did this in one take, the first take and skipped nothing except repetition. If this fails again within 50,000 miles again I might produce a rebuild based off your ideas.
Great video! I have a video of rebuilding a WRX center diff, but it is a bit more crude than yours. I don’t have the car anymore but I know the next guy has had pretty good fortune with it. I used a combo of 50 and 100k cst, but it looks like I should have beefed that up a bit. Nice work!
Hi mate i'm just about to have a go doing this. Thanks for the video. As you started on an 'Outer' plate and ended on an 'Outer' Plate, this would suggest 25 plates and 12 wires, not 24 plates as said. 13 Outer plates, 12 inner plates and 12 wires.
Hey. Excellent video. I also did this operation a few years ago but I think I made a mistake somewhere... it worked well for me for about 25,000 miles then it failed. The liquid I used was 50,000 cst. I think I made a mistake at arranging the discs. My question is if 200000cst is not too thick and will not heat up faster than 50000cst?
It seems to me, combined with your stats, that the 200k reduces the number of rotations. With the 50 or 100k the front half of the drivetrain 'drags' the rear half, engaging before the brakes and engine. So every start and stop engages this coupler, whereas the 200k allows the brakes and engine to not cause this excess rotation of the coupler... i.e. less heat, not more
Sure it will slip less with thicker liquid. Good video but i would put the sealant in to the groove before putting the lock ring back. Thought i need to buy a new one when this fails but seems simple enough to just change the silicone.@@jonmark2688
You don't mention replacing the O-rings or X-rings during the rebiild. The VC ends up as a sealed unit so it can build up internal pressure when the plates slip due to friction/fluid heating. Excellent video, damn useful, but fresh O-rings should be part of the job, any chance you found part numbers for them even though not used? Tx
Interesting video. Thanks for putting it together. So it looks like there aren't any seals keeping that fluid inside the plate chamber? I guess the fluid is thick enough that it can't get out through the gaps? Also curious what keeps oil from getting in although maybe having it filled with fluid keeps the oil out. Pretty fascinating.
hi, there are 2 O-Ring and 2 Quad-Ring to seal it. The 2 O-Rings are easy to buy but the Quad-Rings i could not find online or by any companie in switzerland.
I have a Nissan Rogue that makes the tires squeak at low speeds and they show no abnormal wear or anything. Two different mechanics say they can't find anything wrong. I am wondering if my sway bar bushings are bad since it also feels loose and sways in turns. These tires didn't always squeak so I thought it is weird. I hear those and the links are often overlooked a lot. Why no one can figure it out is a mystery! At this point I would probably take it to a Nissan dealer who would know how it is supposed to ride and feel and they can't find it tell them I want a different vehicle and want to trade it in for something else. It doesn't help them that some people hate their CVT.
Next time try putting it in a vac. chamber overnight before you try putting the top on - you likely have tons of air bubbles between the plates, etc. This will make it a real b**ch to close.
Can you elaborate what you meant with "delay" when describing the symptoms after the first rebuild? In which road conditions did this occur? I am asking this because it somehow makes no sense in regard to the mechanical working principle of this center differential. Under normal driving conditions (high traction, no wheel slip) the viscous LSD doesn't play any role in transmitting torque to the wheels. It is all done by the mechanical parts of the differential (the bevel gears). In this state there should not be any delay even if there was no fluid at all in the viscous unit. It would still be permanent 4 wheel drive, only without any limited slip capability. If the weight of the fluid is too low, this should only be noticable when there are big traction differences between front and rear wheels (ice patches under one axle). This would cause speed differences between the inner and outer disks in the viscous unit and by that, the shearing forces in the fluid would start to force the non rotating parts to rotate which would result in torque transmitting to the slower axle. Another thing to keep in mind is that there should actually be a certain amount of air in the viscous unit to allow the silicone fluid to expand when it gets hot. This is also mentioned in Subarus technical reference manual: "The viscous coupling consists of a number of alternately arranged inner and outer plates and air and- silicone oil mixture filled into a sealed space that is formed by the center differential case and the rear side gear of the differential gear set. The inner plates have their inner perimeters splined to the side gear and the outer plates have their outer perimeters splined to the center differential case. The outer plates are held apart by spacer rings. There are no spacer rings between the inner rings, so the inner rings are movable slightly in axial directions. X-section rings are used to prevent leakage of silicone oil, which would otherwise occur if the oil is pressurized due to large difference in front and rear axle speeds."
Delay... at a red light turning green, I would press the gas and move forward, but then there would be a fluid like 'thud' which I presume was the rear half engaging via the coupler. The same diff rebuilt in this very video is running flawlessly about 9k since
hello and thanks for the video really useful ...so what seems to be the right oil or closer to OEM? the 100k or the 200k ? And what does it change between the two when used?
What probably happens if the center diff is clicking and bad, but it's still driven? Does it stop putting power to the rear wheels eventually? Or the front wheels?
What would you say the 200000cst fluid puts the locking force of the coupler at? I heard stock 4kg is 100000cst fluid. I would think 200000cst being 2x would yield 8kg?
Did you have any bearing noise when you did the initial rebuild? I have a transmission which is giving quite a bit of noise and is just now starting to show binding.
When you initially rebuit the coupling did you replace hardware or only clean and lube it? Mine started clicking about 100 miles ago. My manual transmission oil was 1.75 qt low, so i refilled it but the clicking still clicks.
Hey there i have a 5-speed manual 2004 Impreza Outback N/A that i bought for my son as a first car. Test drove it for 500 miles and it seemed fine. Tagged it for legal driving and 200 miles later i have some kind of binding click noise that happens randomly, but more often when the tires are operating on muddy snow terrain. I can feel the clicking in the stick shift handle. The tranny gear oil was about 1.75 qts low. I filled it and sound is a little less present but still present. Is the center differential lubed by the same gear oil reservoir as the manual transmission? What do you suggest to do? Thanks!
Yes the center differential is lubricated by the gear oil. Even though the manual calls for 75-90 every version of that grade contains LSA (limited slip additive) which the Subaru manual transmission cannot operate with because it is a combination of a transmission and a differential, known as a transaxle. If you have been using 7590 gear oil with LSA added, I would drain out all the fluid and instead use 80 90 gear oil. In the united states, 8090 does not have the LSA which can cause problems in your Subaru transaxle. If that doesn't resolve your problem, then you'll have to open the transmission to see what's going on inside
@jonmark2688 the reason why I don't think it's the transmission gears themselves is because it makes the noise in all gears while in curves or quickly accelerating. It will do it while coasting in all gears as well, but not as much, and only when not going straight. I will refill with 75-140 when I flush it.
@jonmark2688 @rubenbojorquez4614 I'm going to be installing a 300k CST fluid sample in my center diff in the next few months. I'll post my experience once I have it.
Много противоречивой информации по жидкости, которую нужно заливать в вискомуфту. У многих после силиконовой жидкости полиметилоксан с низкой вязкостью от 10000 до 50000 вискомуфта плохо блокируется, и в результате долговременного проскальзывания пригорает и фрикционы склеиватся. При использовании более вязких жидкостей вискомуфта очень плохо проскальзывает при максимальном угле поворота руля, и машина начинает "шагать".
Thank you for what I believe is the MOST THOROUGH, TECHNICAL center differential/viscous coupling repair video available as of December 2023!!!! This will help A LOT!! 👍
I had the same issue on my Subaru Impreza 2016 (Sport Hatchback 5 speed manual transmission). I could not afford the labor prices the dealership asked. Also, it took me a while to figure out that it was indeed the center slip differential that was causing the clicking and clacking when turning at slow speeds, after the transmission came to temperature . I eventually diagnosed it myself watching YT videos. I'm not, by any means, a mechanically inclined person ( basic stuff only but I'd venture to try more complicated things with some help). Tried a couple of "mechanics" and they all misdiagnosed it as "bad CV Axle or wheel bearing". I can't do these repairs myself so I went and spent $650 for a new differential and had a friend/mechanic that put it in for me. It was a HUGE deal in terms of I paid in the end ! This video however got me interested in trying to re-build the old differential which I still have. My question is ... can these things be re-built indefinitely or is there a point where they're just "'done" and a new part needs to be purchased? I ran the car with the clicks and clacks (bad differential) for about a year (took me a few months alone to diagnose it). The old part looks perfect. Intact as far as I can tell. The part number that fit my car is "38913AA102". I also remember that during the process of diagnosing my issue and researching online for weeks, there was a mention of these units as being "sealed" which basically meant "swap the old part with a new one". Perhaps a marketing ploy ... I had no experience with this and "re-building it" was absolutely not even an option I considered but the differential in this video looks exactly like the part that fit my Subaru! Identical! Any help on this is appreciated it! And thank you for making such video! My utmost respect for your effort and expertise!
Just a note (I notice it at the end of the video) -- the retaining ring which holds that back-cover which holds all the inner plates together, is not the same as mine. Mine is basically just a "retainer ring" that has two holes, perhaps for use of a retainer ring pliers. I wonder though, once that comes off which I think it should, everything else inside is the same?
I'm on my 3rd coupler, and it's gonna be the last one I buy, I'm using your video to rebuild these things.
Thank you so much for developing this rebuild. My viscous (38434AA021) is discontinued and very very hard to find a replacement for. I've just completed it on my 1995 WRX STI (used 100k fluid) and can confirm it's working great. I want to add that the older Phase 1 units like mine are rebuild-able using this same process. They are unfortunately welded shut and required machinist work to cut open and reweld after. If anyone has a phase 1 unit like me, I've outlined the rebuild with pictures at thesubaruforums.
On that top plate you removed the plug for the hole or ball bearing. Then you staked in the plug. Great video!
This is quality video/information material! Thank you!
hey, thanks for the updated video on this. I really appreciated your first 3 videos that you made, and also the additional updated info that you put in this one. I do have some criticism for you though. You seem very "rushed" and impatient in the video and you tend to skip forward in the video. I understand that you might not feel the need to show every thing because you have done this procedure a couple times now, but one thing to keep in mind is that there are people watching that have not, and might not even be close to having the knowledge and experience that you do. Leaving the original footage as complete as possible would be very helpful to people watching.
Take your time, If that means splitting up the full video into multiple parts, then do that instead of kind of rushing through everything. Personally I think your original 3 videos were much much better than this updated one because they covered quite a lot more of the process and did not skip over steps like you do in this video. I would encourage you to redo the video again, and maybe put together a loose script for yourself to follow so that you dont sound kind of "lost" and frantic at times. It would also be very valuable for people if you did a video (series?) covering the job from the very start to the finish, I mean the entire job from the very beginning (jacking up the car, drive shaft removal, transfer case removal), all the way to the very end (putting everything back together and cleaning up). yeah I know, it would be a ton of work, but it would be worth it. it would be super helpful to people and would be something that you would never have to come back and redo or think about it again.
anyways, thank you for your efforts with the videos. This video is nice as an update, but feels unfinished and imcomplete when compared to your original videos, I personally think those were more detailed and did a much better job at explaining what you were doing and why you were doing it.
Hello. Thanks for the tips. I did this in one take, the first take and skipped nothing except repetition. If this fails again within 50,000 miles again I might produce a rebuild based off your ideas.
Thank Christ I finally found some info to fix my wife’s car. Thank you sir. Thank you, thank you, thank you!
Damn. Good job and outstanding post production efforts. Cheers from Long Beach, CA
Great video! I have a video of rebuilding a WRX center diff, but it is a bit more crude than yours. I don’t have the car anymore but I know the next guy has had pretty good fortune with it. I used a combo of 50 and 100k cst, but it looks like I should have beefed that up a bit. Nice work!
thanks this makes me feel confident enough to do it myself. very helpful bro
Hi mate i'm just about to have a go doing this. Thanks for the video. As you started on an 'Outer' plate and ended on an 'Outer' Plate, this would suggest 25 plates and 12 wires, not 24 plates as said. 13 Outer plates, 12 inner plates and 12 wires.
I appreciate the info! I have 2 100k cst bottles to rehome now 🤣🤣🤣
Hey. Excellent video. I also did this operation a few years ago but I think I made a mistake somewhere... it worked well for me for about 25,000 miles then it failed. The liquid I used was 50,000 cst. I think I made a mistake at arranging the discs. My question is if 200000cst is not too thick and will not heat up faster than 50000cst?
It seems to me, combined with your stats, that the 200k reduces the number of rotations. With the 50 or 100k the front half of the drivetrain 'drags' the rear half, engaging before the brakes and engine. So every start and stop engages this coupler, whereas the 200k allows the brakes and engine to not cause this excess rotation of the coupler... i.e. less heat, not more
Sure it will slip less with thicker liquid.
Good video but i would put the sealant in to the groove before putting the lock ring back.
Thought i need to buy a new one when this fails but seems simple enough to just change the silicone.@@jonmark2688
Informative video thanks paaal! You just saved me $650
You don't mention replacing the O-rings or X-rings during the rebiild. The VC ends up as a sealed unit so it can build up internal pressure when the plates slip due to friction/fluid heating. Excellent video, damn useful, but fresh O-rings should be part of the job, any chance you found part numbers for them even though not used? Tx
Interesting video. Thanks for putting it together.
So it looks like there aren't any seals keeping that fluid inside the plate chamber? I guess the fluid is thick enough that it can't get out through the gaps? Also curious what keeps oil from getting in although maybe having it filled with fluid keeps the oil out.
Pretty fascinating.
hi, there are 2 O-Ring and 2 Quad-Ring to seal it. The 2 O-Rings are easy to buy but the Quad-Rings i could not find online or by any companie in switzerland.
I have a Nissan Rogue that makes the tires squeak at low speeds and they show no abnormal wear or anything. Two different mechanics say they can't find anything wrong. I am wondering if my sway bar bushings are bad since it also feels loose and sways in turns. These tires didn't always squeak so I thought it is weird. I hear those and the links are often overlooked a lot. Why no one can figure it out is a mystery! At this point I would probably take it to a Nissan dealer who would know how it is supposed to ride and feel and they can't find it tell them I want a different vehicle and want to trade it in for something else. It doesn't help them that some people hate their CVT.
Next time try putting it in a vac. chamber overnight before you try putting the top on - you likely have tons of air bubbles between the plates, etc. This will make it a real b**ch to close.
Can you elaborate what you meant with "delay" when describing the symptoms after the first rebuild? In which road conditions did this occur? I am asking this because it somehow makes no sense in regard to the mechanical working principle of this center differential. Under normal driving conditions (high traction, no wheel slip) the viscous LSD doesn't play any role in transmitting torque to the wheels. It is all done by the mechanical parts of the differential (the bevel gears). In this state there should not be any delay even if there was no fluid at all in the viscous unit. It would still be permanent 4 wheel drive, only without any limited slip capability.
If the weight of the fluid is too low, this should only be noticable when there are big traction differences between front and rear wheels (ice patches under one axle). This would cause speed differences between the inner and outer disks in the viscous unit and by that, the shearing forces in the fluid would start to force the non rotating parts to rotate which would result in torque transmitting to the slower axle.
Another thing to keep in mind is that there should actually be a certain amount of air in the viscous unit to allow the silicone fluid to expand when it gets hot. This is also mentioned in Subarus technical reference manual:
"The viscous coupling consists of a number of alternately arranged inner and outer plates and air and-
silicone oil mixture filled into a sealed space that is formed by the center differential case and
the rear side gear of the differential gear set. The inner plates have their inner perimeters splined to
the side gear and the outer plates have their outer perimeters splined to the center differential case.
The outer plates are held apart by spacer rings. There are no spacer rings between the inner rings,
so the inner rings are movable slightly in axial directions. X-section rings are used to prevent leakage
of silicone oil, which would otherwise occur if the oil is pressurized due to large difference in
front and rear axle speeds."
Delay... at a red light turning green, I would press the gas and move forward, but then there would be a fluid like 'thud' which I presume was the rear half engaging via the coupler. The same diff rebuilt in this very video is running flawlessly about 9k since
Good video, can you tell me the specifications or what type of high density fluid you use to lubricate the inside of the core?
hello and thanks for the video really useful ...so what seems to be the right oil or closer to OEM? the 100k or the 200k ? And what does it change between the two when used?
Greetings! Tell me, how does a viscous coupling behave with 200 thousand oil?
I don't get it. You took it apart, cleaned it, and reassembled? why not replace the clutch packs? Why not just replace the entire unit
What year is this out of? Sti? Wrx? Great video!
What probably happens if the center diff is clicking and bad, but it's still driven? Does it stop putting power to the rear wheels eventually? Or the front wheels?
Hi Jon. Is everything still ok with 200,000 cst after all this time? I'm asking because I'm about to rebuild mine. Thank you very much.
What would you say the 200000cst fluid puts the locking force of the coupler at? I heard stock 4kg is 100000cst fluid. I would think 200000cst being 2x would yield 8kg?
Did you have any bearing noise when you did the initial rebuild? I have a transmission which is giving quite a bit of noise and is just now starting to show binding.
When you initially rebuit the coupling did you replace hardware or only clean and lube it?
Mine started clicking about 100 miles ago. My manual transmission oil was 1.75 qt low, so i refilled it but the clicking still clicks.
Hello, how is the 200k fluid holding up ?
holding up just fine. Sold recently and no complaints from the new buyer!
Download video file your?
2017 forester 6spd manual failing at 52k miles....
Hey there i have a 5-speed manual 2004 Impreza Outback N/A that i bought for my son as a first car. Test drove it for 500 miles and it seemed fine. Tagged it for legal driving and 200 miles later i have some kind of binding click noise that happens randomly, but more often when the tires are operating on muddy snow terrain. I can feel the clicking in the stick shift handle.
The tranny gear oil was about 1.75 qts low. I filled it and sound is a little less present but still present.
Is the center differential lubed by the same gear oil reservoir as the manual transmission?
What do you suggest to do? Thanks!
Yes the center differential is lubricated by the gear oil. Even though the manual calls for 75-90 every version of that grade contains LSA (limited slip additive) which the Subaru manual transmission cannot operate with because it is a combination of a transmission and a differential, known as a transaxle. If you have been using 7590 gear oil with LSA added, I would drain out all the fluid and instead use 80 90 gear oil. In the united states, 8090 does not have the LSA which can cause problems in your Subaru transaxle. If that doesn't resolve your problem, then you'll have to open the transmission to see what's going on inside
@jonmark2688 the reason why I don't think it's the transmission gears themselves is because it makes the noise in all gears while in curves or quickly accelerating. It will do it while coasting in all gears as well, but not as much, and only when not going straight. I will refill with 75-140 when I flush it.
@@jonmark2688 There are plenty of 75W-90 gear oils that don't have the LSD additive.
is the front center diff and viscous coupler one component?
It isn't a "front center diff". The car has a front differential, a rear differential, and a center differential. They are independent of each other.
i swapped one out on a crosstrek recently … now i have the coupler to open up n rebuild
hey great video @jonmark2688, how did it work with 200,000 CST? I am about to do the whole thing.
still working amazing. at least 6k since the change. I drive a lot
@jonmark2688 @rubenbojorquez4614 I'm going to be installing a 300k CST fluid sample in my center diff in the next few months. I'll post my experience once I have it.
@@NickSchuetzehow is it going?
Много противоречивой информации по жидкости, которую нужно заливать в вискомуфту. У многих после силиконовой жидкости полиметилоксан с низкой вязкостью от 10000 до 50000 вискомуфта плохо блокируется, и в результате долговременного проскальзывания пригорает и фрикционы склеиватся. При использовании более вязких жидкостей вискомуфта очень плохо проскальзывает при максимальном угле поворота руля, и машина начинает "шагать".