I have a 2002 Subaru legacy wagon, 185k miles, 5 speed manual, thumping noise when making sharp turns at slow speed, happens only after I drive over about 10 miles, does not happen after the car sits for any length of time.
Thumping noise on a sharp turn is most likely a bad CV joint.
In addition to a bad CV joint, a bad center viscous coupler could be the problem.
Has this car ever been run with mismatched tires?
If the answer is “yes”, then my money is on a worn-out center viscous coupler.
Thanks for the reply - no mismatched tires but not rotated very often. Subaru dealer wants to replace one axle then another and see if something fixes the problem. Then maybe something related to the transmission. Odd that it only occurs after driving more than about 10 miles.
If you have been running the car with unevenly worn tires (not rotated often enough) then my money is on the center viscous coupler that VDCdriver mentioned. It is happening after 10 miles because it is heating up due to the uneven rotational speeds of your tires. It takes a few miles for the coupler to get hot and then it starts to thump. I hope I am wrong because you will NOT like the cost of the repair if it turns out the viscous coupler is shot.
“no mismatched tires but not rotated very often”
Actually, when it comes to an AWD vehicle, “mismatched tires” can mean any of the following:
Use of different brand/size/tread pattern/tread wear tires
Use of a donut spare for an extended period of time
Failure to rotate the tires on a consistent (every 5k or every 7.5k miles) basis
Just as there is a reason to change the oil on the schedule provided by the mfr, it is also vitally important to rotate the tires on the recommended schedule, and mechanical failure is often the result of failure to rotate the tires consistently on an AWD vehicle.
I fear that the OP is going to learn–the hard way–that he should be faithfully following the mfr’s maintenance schedule–in all respects.