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Car Shaking at highway speeds, Acceleration only

So I hit a bad pot hole a month ago. Next day noticed the car shaking at around 60mph acceleration only. Idle and coast is smooth. Replaced the front right tire with my full size spare to test it out. Still shaking. Went to a shop and dropped off the front right tire to be checked. He said tire was bad get 2 new ones. Got two new ones, still shaking. Then he said ball joints where bad, fixed front joints, still shaking. After research I found AWD especially Subarus don’t like non all matching tires and could be causing the problem. So I plan to get the remaining 2 tires to have all matching set and see/hope it works. But I’m weary of this being the actual issue or is the shop screwing me. All my research results in almost exact symptoms pointing to possible CV joint, Tie Rods, Struts, timing belt? I would think this shop would check these things. Is a very noticeable shake at high speeds, acceleration only really possible with just having 2 different tires in the back?

2003 Subaru Forester XS 190k miles

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all 4 former tires had even tread depth? now you have 2 new tires. are they cheapo tires? walmart specials?

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they are cheap ironman brand, well $80 which was cheapest he could find (so he says). He’s foreign so tough at times to understand but said things like “well the different speed ratings of the tires could be the issue”

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Non-matching tires will inevitably lead to failure of the Center Viscous Coupler–which is why the Subaru Owner’s Manual is very specific regarding the importance of matching tires. However, that being said, a failing Center Viscous Coupler would be much more likely to produce binding of the drivetrain and scrubbing noises from tires on low-speed sharp turns–as in situations like parking garages.

So, I urge you to get a set of matching tires–even if they are cheapo tires–in the hope that you can avoid having to replace that viscous coupler, but I doubt if that expenditure is going to cure your shaking on acceleration problem. That problem is much more likely to be related to bad CV joints.
:thinking:

i got 4 nice winter tires 2yrs ago for $50. had 95% tread. 215/65/17 approx? sold them to a guy with a 08 or so subaru. we met at neutral site in january and i looked at his tires and the rears were 99.9% bald. i could not see any tread. and the fronts were not much better. he had teen driver with him. yep, today is your lucky day. subby and new snow tires.

Concur, CV joint damage is where to start looking.

CV joint for sure, but a good front end shop will check everything including tires, rims and other suspension components. It’s not rocket science and the owner shouldn’t have be diagnosing the problem for a good mechanic/ repair shop. :wink:

Yup.
The Subbies I had were the same way. They are programmed to send power to all the wheels, all the time. That makes them a little more susceptible to tire diameter differences. Slip and grip system are not engaged till needed and the tire differences are not a factor all the time. From what I was told, like the differential gears of a differential, they tend to degenerate heat if they constantly have to work with tires of unequal diameter. Even though ALL cars should have the same tread and same diameter, it seems a little more problematic for subbies. No big deal if you’re careful. They will last longer then most two wheel drive cars as they are quite robust. The Audi has a similar set up.