I have rebuilt all of my drive components except for rear end gears. The same noise problems prompted me to do mine.
1) I would start with the U joints on the driveshaft first, because it's the easiest. If you get a clunk when shifting fro reverse to forward, that's a good tip-off. Although they can be worn without showing any loosness. A good test is to grab the driveshaft and see if there is any wiggle or slop in the joints.
U-joints are pretty cheap and easy to change. You will need to loosen the brake cable and remove the bolt from the pulley to allow the driveshaft to drop down. Loosen the 4 bolts at the transmission tailshaft and push the tailshaft in towards the transmission to get the joint yoke separated and the driveshaft will drop down.
The rear end will have to be off the ground so you can rotate the driveshaft to get to the bolts on the rear of the driveshaft. Loosen the bolts on the yoke clamps with a 12 point box wrench or a 12 point socket on a 2-1/2Ft. extension shoved down the tunnel that the driveshaft goes through. Pry the u-joint loose as you pull on the driveshaft.
Take the whole thing out and set it on a bench. If the caps fall off while you are doing this, it's a pretty good bet that they are worn, or out of grease or both.(21 Years is a long time for grease to last.) Remove the c-clips that hold the u-joints into the driveshaft, and press the bearing caps out of the housing. If they are worn,you will see a lot of shiny wear marks inside the caps and maybe a flat needle bearing or two. Put in the new U-joints and reverse the procedure to re-assemble. Some new joints don't fit in the yoke, as they are fatter in the center of the "Cross". If so, swap the caps and needle bearings from the new set onto the original Cross and it should be OK. Make sure there's plenty of grease on the bearings and that should keep them from dropping off while you are putting the driveshaft back together.
Or, it might be:
2) Half-shafts. These are just like the drive shaft, on the output sides of the differential between the rear end and the rear wheels. Same procedure to replace as driveshaft.
Or, it might be:
3) Rear wheel bearings. Check for play up and down on the rear wheels. The bearings could be worn and if so, you will hear a grinding noise. You may also get some vibration at high speed that feels like an unbalanced tire, that you feel at the steering wheel if the wheel bearings are worn.
The typical bearing clearance is around 0.010", but good shops will do it to 0.005". So if it moves any more than that, it's probably worn.
I leave this job to a professional, since you need about $300.00 worth of tools and shims to do rear wheel bearings.
So much for my experience with my '82.
Good luck!
