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Howdy -- My first post here. I'm impressed with the useable technical information I've seen here; hope someone can address this...

 

'99 Forester L, (mt, regular front and rear differentials) -- feels like the viscous coupling unit in the center diff. is going south -- drive train binding in sharp turns after warm-up. I've read all the threads on torque bind, etc.

 

Has anyone replaced this unit themselves? Is it something an experienced shade tree mechanic can do? Is the unit available anywhere except a dealer?

 

Any advice, experiences, portents of doom, etc. welcome. Thanks very much -- George

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hey,

 

had my VC replaced- current thread running from Hawksoob about this topic. I had a mechanic do the job for just under 500 because he had a good source on the VC (only about 250 bucks for the unit). he claimed it was a pretty easy job, but i, being a medical student, had very little time and or inclination to fix the sub myself (i used to be a volvo nut, and by virtue, a shade tree mechanic). i think there are suppliers out there- i will try to get this guy's number and get a line on his supplier.

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George , I have a 99 Forester AT. However, I have been reading the various Subaru boards for a number of years. First, viscous coupling units do fail, but it does not appear to be a very common problem. Second, when the viscous unit fails the typical symptom is a loss of AWD. Usually the driver is unaware that the viscous unit has failed until he gets stuck in snow and then notices that the rear wheels aren't turning. I guess that it could happen, but I have never read of a viscous unit failure causing binding during sharp turns. When the multi-pack in the AT goes, that almost always causes binding.

I wouldn't be so certain that the viscous diff is the problem. I would check the front end and steering just to make sure. You don't want to replace a fairly expensive part, and then find out it was the wrong one.

Perhaps one of the more experienced mechanics on this board could provide some additional advise on this problem.

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I own a 90 Lagacy AWD 5/m with 210k I don't think the viscous coupling has ever been changed. When making slow tight turns (ie, turning in to a parking space) my car shudders a little, this is normal. If the viscous coupling unit went out you would have either no drive (unit is not coupling) or vary notisable binding (unit is locked up). A quick way to tell if the unit is locked up is to jack up one tire and try to turn it . If it turns with some resistance your OK if not The unit is locked up. Good luck

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my understanding of the VC is it works like an lsd in a rear axle, you only lose drive (assuming its failed ) if one wheel has lost traction and same with awd if the vc is not working you only lose drive if any of the 4 wheels has lost traction?

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  • 4 weeks later...

Sorry for the long lapse; thanks for the replies. Scubaroo, good suggestion on turning a rear wheel -- it doesn't; compared it with another Forester MT -- it does, so I'm concluding the unit is bad. A local shop corroborates this diagnosis.

 

CardinaA -- any info on where your mechanic procured a new one? Thanx! -- George

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hey george,

 

i can't seem to find his # (or the receipt for the job, for that matter). also, is your car a manual or auto? mine is manual, so i don't know details on the automatic pathology of viscous coupler (clutch pack) death.

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manual L series with 100,000 miles. If both wheels are off the diff just lets one wheel be spun. The driveshaft stays in place. This is with the five speed in reverse and emergency brake off. If I jack up the right rear wheel and leave the left down the tire cannot be spun. It just takes up driveline play. This makes me think the VC stays engaged all the time.

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Its the only explanation I can see. My understanding (based on theory and research, not experience) is that the unit should permit differential rotation between front and back when there's a small difference in rotational speed, but begin to lock as rotation differential increases (as when front wheels start to slip under power). Thanks for the input -- George

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