okay it just appeared recently when i was driving. sometimes when i shift theres like a *thump* in the rear, and it does it even more when i'm reversing. i don't know where the heck this came from, i just can't figure it out. also my speedo just suddenly stop also if this is of any help. car is an 88' s4 na with gxl rear subframe.

 

Hmm, I'd take a wild guess it's because of the messing around with the rear subframe... Diffwrential mounts maybe?

 

mine did this, the front differential mount came out in three pieces. it also had bad backlash in the axles which may have contributed.

 

Check the rear Differential Front Mount,also the Two Big 21mm(?) bolts that hold the Diff up to the Car.....#2:the speedometer cable may be loose at the Transmission..check the Round Coupler that goes onto the Threaded portion of the transmission where it Connects there...another final note is to check the driveshaft for bad Universal joints.

 

thanks for all the help, i'll check it out tomorrow and get back to you guys if i find the problems.