I'd at least check the disks first. The front one on mine was in pretty poor shape and it did create "clunks" that sounded as if they could have come from the tranny. My rear flex disk is "aftermarket" and creates a similar type of clunk (on downshifts as it turns out) that also could be interpreted as a worn or loose rear-end. The independent shop I use says that they've rarely had to work on the transmissions even though they shift so hard.
89 190E 2.6