Another factor whenit comes to th driveshaft is the "clocking" of the U-joints. That becomes an issue if the driveshaft halves are not reinstalled in their original (as manufactured) positions. By "clocking" I mean this--If the first flange attached to the transmission has its loops horizontal to the ground--the rear most flange (attached to the diff) has to have its loops vertical to the ground--in other words --imagine the front flange and rear most flange aligned together they would form a comlpleted U-joint. Of course--that alignmment can be attained with one half also rotated 180 degrees. But only one of those 2 positions will be correct for balance. Having worked on rear drive Volvos for neasrly 50 years I've never heard of shimming the center support bearing. If the angle has changed (at the rear) that could only happen if the springs are severely worn out. The rear can tolerate un-ideal angles such as having rear seat passengers or heavy things in the trunk. if the angle of the front half has changed the fault has to be motor/tranny mounts. - Dave