Gears & Axles - gear problem

alright i looked everywhere and couldnt find anything on this, so , i have a 99 firebird 3800 and i new a guy that had a rear end just lying around from the 01 t/a he wrecked . he wanted 200 for it so i bought it off of him. it has 342 the only thing wrong with it is that 2 bolts holding the gears keep coming loose . so my question is how do i fix that? my next question is the t/a it was on was a m6 and i have a a4 does it matter about the driveshift at all?

get new ring gear bolts there probably streched so they wont torque right

where can i find those

Try these guys first; if they can't help then go to the local dealership
SDPC (http://www.sdpc2000.com/cart.asp?action=catalog_start&catid=873)