Had the same symptoms in my '88 recently. "Clunk" noise on changing directions and when going over dips or cornering. Outer unis were the problem. Couldn't feel any movement while on the car but trunions badly marked. If you find the same, I suggest doing all 4 as the inners were dry and on their way out.
Replacement unis have grease nipples (not so on originals). Have the unis fitted so that the nipples all face the inner (diff centre) otherwise you can't get a grease gun on them.