Rear differential 2001 Subaru Forester

When I make sharp turns forward left or right and when I back up and turn left or right my car feels wobbly/grinding. My mechanic says he thinks it “may” be the rear differential needing servicing for around $100-$110. I have 135,000 miles. Does that sound right? There is no noise associated with this sensation. Thanks…

Is he a Subaru specialist? If not, you’ll want to find one. The cheaper problem would be a bad CV joint in one of the axles. If not, it could be in the center differential, or maybe the rear, but unless it just needs fluids changed (use the exact diff fluid specified by Subaru), it’ll be more than $100…

Have you always been careful to use tires with matching circumferences over the life of this car?

I agree with texases, and–unfortunately–I suspect the center differential.
If the OP has driven the car with mis-matched tires, that make the center differential scenario much more likely. I think that the rear diff is a very remote possibility–unless it was run with insufficient gear oil.

He is not a subaru specialist, but has done a lot of work on my car in the past. Yes, I have always had same tires circumference over the life of the car.

Wait…I had a flat a couple of months ago and they replaced the tire with “the same” goodyear tires I had already, but the tread looked different. They said that goodyear had changed the tread look, but it was the same tire. Thank you!

To be clear they replaced that one tire (not all). So there is one tire that has a different look sideway (not tread)…sorry…

sidewall…instead of sideway

Is it possible to have the same tire, but new sidewall look? How can I be sure the tire circumference matches. Thanks so much…

The issue is the tire diameter, and new vs. worn can cause a problem. If it’s much different than the old tires, it can damage the center differential. How many miles were on the old tires at the time the one tire was replaced?

Purchased new set October 2010 at 102, 000 miles. Now have 135,000. Probably put that latest tire on about 4 thousand miles ago.

This latest information makes me even more sure that the problem lies in the center differential.
“Matched” tires with an AWD vehicle means:
Same size
Same tread design
Same amount of tread/same circumference

A difference of almost 30k miles between the new tire and the older ones is almost definitely enough of a difference to cause problems with the center differential, and a competent tire shop or mechanic should be aware of this.

The next time that you need one new tire, you can have the tread “shaved” so that it matches the circumference of the other 3. Since this was not done, unfortunately, I think that you may be looking at a repair bill in the range of $500-700.

You may have to search a bit to find a tire shop that “shaves” tires, but the inconvenience is worth it.

I agree with @VDCdriver - you might click on ‘Mechanics Files’ above and see if you can find a Subaru specialist near you. This is one aspect of Subarus that causes problems (in addition to the head gasket issues).

Wow…I had no idea! I am not sure the tread is different, just the sidewall “look” of the tire. They said it was the same tire. So, even if you put the same tire on the age of the older tires can cause the same issue.

Yep, it’s caused by the difference in circumference of a new tire vs. an old tire. If the difference is enough it causes the differential(s) to constantly ‘engage’, they’re designed to do that for short periods when tire speeds differ due to slippery conditions. When the tire speeds differ due to tire circumference the constant, mile-after-mile engagement can wear out/damage the differential(s).

klynne–I’m honestly not trying to beat you up over this sad situation, but the Owner’s Manual does tell you about the importance of properly matched tires, with essentially the same details that I provided earlier. The manual doesn’t go into detail regarding the mechanical problems that will result from mismatched tires, but it does tell you that it is very important to have tires of the same brand, same size, same tread pattern, and same circumference.

Even though most people don’t see the necessity of reading the Owner’s Manual, this is a perfect illustration of why you need to do it as soon as possible after buying a car. And, if somebody buys a used car w/o a manual in the glovebox, they need to buy a manual. E-bay is usually a good source for low-cost copies of manuals.

But, even if you were unaware of this potential problem, whoever sold you that one tire should have been aware of it. If your mechanic was the one who sold you one tire, that should give you one additional reason to not return to his shop again.

Well I was told it was the same tire except a change in design of sidewall. I am the one that noticed the sidewall difference…yes I was trying to purchase the same tire tread as the other tires thus my observation of the sidewall. I agree about the drivers manual. It sounded like in an earlier post that the age of the tire, even if it is the same brand/style/tread, can make a difference. That’s what I want to be sure of before I go back to the mechanic…do I question if it is really the same tire? or can the age difference in tires of same tread make a difference. Thanks so much.

It’s the fact that the old ones are worn 30,000 miles, and therefore smaller in circumference, than the new tire that might well have caused the problem. That problem would exist even if the exact same brand/model/size tire had been installed.

Thank you! That helps. So is it advised to buy two new tires when one goes bad to avoid this?

Unfortunately, because of the Subaru’s AWD it’s recommended to buy all 4. Alternatively, you can get the one new one ‘shaved’ to equal the size of the 3 others, if you can find a shop that does that.