1st Gear Member
Join Date: Mar 2004
Location: New Hampshire, US
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Bearings + controll arm assembly will cost you about $300 (both sides).
Split is almost exactly even.
In your place I would replace both: you're already there...
I am not a service tech, but do all car work, I can, myself...
I do not know of any way to troubleshoot bearing vs controll arm on a driveway.
Bearings and bushing failure manifest itself in the noise, as you know, which is caused by excessive clearance. What is the method to measure clearance in the car suspension? Components weigh about 60lb on each side, plus they are preloaded with about 400lb springs. This takes all the clearance out and who can wiggle 400lb to see if there is a play? Most likely component to fail? But you already know: BMW rear wheel bearings and control arm bushings, though I think I have heard of front suspension bushing failure, not rear... I think...
The only way, I can think of, to take bearing out and diagnose it on test fixture. Same with bushings. But if you go to those extends.... Just replace them.
Sorry man, cant help much just do bouth and be done...