Check anything that revolves that can be loose. I'd start with the fan belt tensioner bearings, PS and water pump, and alternator. Check that the crank pulley is tight. Next move to the transmission bell housing bolts, drop the starter and make sure the convertor bolts are tight. Next check your driveshaft ujoints to see if they are in good condition. If you have a two piece driveshaft, check the saddle bearing rubber to see that its in good condition. Last, check that the pinion nut has not loosened up on the third member.