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How do you bench test these?

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

This is quality video/information material! Thank you!

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

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.

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.

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".

Download video file your?

is the front center diff and viscous coupler one component?

Thank Christ I finally found some info to fix my wife’s car. Thank you sir. Thank you, thank you, thank you!

Hello, how is the 200k fluid holding up ?

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.

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?

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.

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.

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?

What year is this out of? Sti? Wrx? Great video!

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?

2017 forester 6spd manual failing at 52k miles....

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."

On that top plate you removed the plug for the hole or ball bearing. Then you staked in the plug. Great video!

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.

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?

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!

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!! 👍

hey great video @jonmark2688, how did it work with 200,000 CST? I am about to do the whole thing.

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.

Greetings! Tell me, how does a viscous coupling behave with 200 thousand oil?

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!

I appreciate the info! I have 2 100k cst bottles to rehome now 🤣🤣🤣

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.

thanks this makes me feel confident enough to do it myself. very helpful bro

Informative video thanks paaal! You just saved me $650

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?

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.

I was lookin for Subaru differential rebuild but found this in your uploads. Thank you for creating this reminder. Praise YHWH and Yeshua Hamashiach!

Nicely done. The music, movement, coloring and tones all empower the direction instead of hinder 🙏 also like how it didn’t skip too much, I had time to read!