Begin by removing the exterior snap rings which retain the u-joint caps

You must remove the lower joint first

On the left you see the centering ball and needles within. On the right you see the post that rides on the needles, and the spring in the post

New centering ball, Napa part #612.... but that seal (on the lower left) does not work. Call a competent driveline shop and find a better solution. You might try Spicer part #404-0A

New rubber seal which surrounds the centering post. Try Spicer part # 412-2

This seal has a small lower metal lip. I used a large socket of the appropriate size to tap it into place

I installed the centering ball in a similar fashion, using a socket to drive it in

THIS IS THE HARDEST PART. You must drop the post and spring into the centering ball without disturbing any needles. Note you must have NO caps installed on that lower u-joint at this time

Be certain that your zerks (or nubs for zerks) are pointing away from each other or angularity will suffer. Screwdrivers point at nubs

Let the rear axle free-hang and check for binding by turning the d/s. If binding is detected you can grind a bit here......

.........and here