1972 Ck-10 4x4

[Keith Wilks]

I have replaced approx. (3) complete rear-ends in my 72 4x4 over the 15 years I have driven it. It always sems to start with the pinion bearing seal going out and water / dirt entiering the differential housing. Could this p. seal be getting damaged by the excessive amount of slack in the drive train? It's an automatic transmission and going out of park to reverse / drive really makes a clang a lot of the time. I thought after this last rear differential rebuild that some of the slack would be taken out, but it is still there.

Where would I start looking to take the slack (spin up) out of the transmission, transfer case, and rear end. When I say slack or spin up I am talking about the amount of rotation in the drive shaft before it stops after engaging the transmission.
Thx,
K.