The driver's side rear shock makes a thud noise when I hit a bump. I had the same thing happen last year with the passenger side and it was caused by a failed weld on themetal "cap" that the top of the shock where it bolts on.
I replaced that metal cap and solved the problem, but I can't remember where I ordered it from. Someone from here gave me the link to a parts place where I got the part for $15.

Anyone know what the part is called or a good online Volvo parts place that I can search for the part (with diagrams)?

Thanks a million!

 

Probably here:

http://www.fcpgroton.com/volvo.htm

 

Yep, that was it! Thanks Jim!