There are six bolts attaching the rear to the frame; in my experience, the front two are usually the biggest issue, as when they work loose, sometimes the bolts that attach the brackets between the frame and rearend loosen, and then it cracks the mounting ears on the transmission.
I would also generally look for hydraulic leaks. If there is fluid coming out of the top of the steering column, the column needs to be rebuilt, which costs about $100 for parts plus a few hours of your time. If you are able, reach up from underneath and try to wiggle the driveshaft. If it moves radially, the couplings are probably worn, and if they are bad enough, it'll damage the input shaft on the transmission. Drive it around, and turn the steering lock to lock. It should operate consistently without jerking or making funny noises.
Parts for these get a little spendy and add up quickly for these, so get it cheap if it needs a lot of attention.