2002 Subaru Forester, 5sp. Manual Trans. -Clutch - Viscous Coupler - Rear Differential repairs

My 02 Forester with 135K miles started to fail to accelerate at an equivalent rate to the rpms once shifted into gear and the clutch released. I think this is called “slipping.” I took it to my local mechanic who said the clutch was bad. $1,200 repair. Two weeks after the repair, the problem came back just like before. I took it back and this time they said it was the transmission, the viscous coupler to be exact. $2,600 repair. Four days later the problem was back. This time they tell me that the rear axle was slipping out of the differential because a clamp was loose and broken. The clamp was part of the differential and it had to be replaced. $700 repair.

Can anyone help me understand if they could honestly make this progression or should they have been better able to diagnose the problem?
Thanks for any help or guidance you can offer!

On my Ford truck at least, if the differential were slipping, there’d be a lot of noise from the gears clashing I expect. Your truck may be a different rear axle design though. I have no idea what a viscous coupler would do in a truck with a manual transmission. I’d expect to hear that phrase more in respect to an automatic transmission. Is your truck 4wd? Maybe that has something to do with this.

Anyway, it sounds like there is indeed something slipping between the engine output shaft and the rear wheels. With no weird noises, it would be reasonable to think it was the clutch. I’m surprised that didn’t fix it. If a “clamp” is broken on the differential, well, that has to be fixed, but I’m doubtful that is what is causing the slipping. I can’t think of any part that would be referred to as a “clamp” on a rear differential though.

I’m thinking the problem is still the clutch is slipping. Either the mechanic got some grease on something during the install, or forgot to clean everything off first before installing the new parts. It’s not possible to tell via the internet of course. You need a qualified mechanic to give it the once over, there, in person. Given what you say though, you might want to consider getting a second opinion before allowing the current shop to proceed with any more repairs.

Edit: There’s another possibility, the clutch linkage needs to be adjusted or the hydraulic system re-bled.

From a distance, I can’t determine whether there ever was a clutch problem with this vehicle, but–if there is/was a problem with the center viscous coupler and the rear differential, I have a very strong suspicion that one or more of the following conditions caused it:

Failure to rotate the tires on a consistent schedule, at approximately the same mileage interval each time
Buying tires in sets of less than 4 at a time, thus leading to running with tires of widely-varying tread depth/circumference
Using a compact (donut) spare tire for more than a very limited number of miles.

Center viscous couplers and differentials on Subarus normally last the life of the car unless the owner has run with mis-matched tires. So, if the OP (or possibly a previous owner) ever allowed any of the scenarios detailed above to take place, that would explain the OP’s recent mechanical problems.

Edited to add:
The last repair–to the differential–could have resulted from a screw-up on the part of the mechanic when he repaired/replaced the center viscous coupler. My best guess on that repair is that he did not secure the driveshaft properly when he re-installed it following repair to the center viscous coupler. In addition to wondering about the tire issue mentioned above, I am beginning to wonder about the competence and honesty of the OP’s mechanic.

One of the few times a car should be evaluated by a dealership. Repair by experimentation makes independents without a manufacturer’s service resource suspect. Once you get to the drive train of awd, go to the horse’s mouth.

Also,With awd, you will need to service those extra differentials, center and back. fwd cars often include the transmission service with the differential service using the same fluid. When they own an awd car and don’t use dealer service, some tend to forget that and never service them…till they die early. So, they will last the “life of the car”, but only if you service them.

Thanks for the input. I guess my biggest question is do you guys think I was taken to the cleaners by my mechanic?

It seems to me that they should have found the problem in the rear differential earlier. If not right off the bat, certainly before they tore into and repaired the viscous coupler which was the most expensive repair.

@Wendy80501–Can you please respond/react to what I theorized in my earlier post?

Yes, I suspect that your mechanic is…less than skillful…and, perhaps less than honest…but it would be helpful if you let us know what you did or did not do regarding the tires while you have owned this vehicle. Also…are you the original owner, and…if not…do you have the previous owner(s)’ maintenance records?


At this point, I have more questions than I have answers…

I have only owned the car for two years, and put four new matching tires on it for the four worn out ones that were on it. While I cannot say for sure that the prior owner was as responsible, he did seem to be a “car guy” and loved his Subaru, and bought another new one.

When I read about symptoms of a bad viscous coupler, I see things talking about clunking, and tires not rolling freely, and these thing happen when the wheel is turned. Non of these things happened in my car, it only slipped and continued to slip.

Details are still sketchy to me but this comes across as some guesswork and somewhat high ;prices for that work although there may be something there not readily apparent and which then skews my view a bit.

Maybe the clutch was not installed correctly and with continued problems the blame is simply being shuffled off onto other assemblies.

Unfortunately, you will never find out for sure till you take it to someone more qualified and directly involved in the problem now. Is it working now ? I had a problem a couple of years ago that was diagnosed incorrectly by both a dealer and an independent. Only when I went back to the dealer but after communicating with the manufacturer myself did they then use a manufacturer’s rep advice in diagnosing the problem. The problem was then fixed. It was a much cheaper and easier fix and I got the manufacturer to spring for it. It was out of warranty. Only a dealer or you as an owner directly often use those resources. Had I gone with an independent only, I would have had something fixed that didn’t need to be and been positioned like you were with another “fix” on top of it. Awd and 4 wd drive components are often very specific to the make and independents don’t have the right resources or correct tools for the job sometimes. But, they will still take your money and claim they do. When anyone tells me I have an expensive repair, I always the manufacturer directly. It has only occurred a couple of times, but it has saved lots of money both times. The manufacturer has nothing to loose or gain but their reputation if they aren’t forthcoming. For your own satisfaction, contacting Subaru directly might shed some light. It is a hassle, you will have to be patient and find the right person on the other end.