HO style rear end snubber

[wolfthing2000]

I am not sure what it is called for sure but I can understand what it does. I picked up a complete axle assembly today from a 72. The third member is the HO drop out style and there is a large bolt with a flat to turn with say a crescent wrench and a lock nut that is quite large on the drivers side front of 3rd member that screws through the side of the case and supports or puts pressure against the ring gear maintaining a good mesh at the pinion under heavy load. I have heard of it being discussed on this sight.
Who knows or how do we go about adjusting such device????
There is also a wear pattern on the back of pinion indicating where it's "puck" ( I have heard it called) was riding against the face opposite the ring gear teeth. A good idea it seems.
My Motors manual shows some axles for Chevrolet that have it , but they are shown only for the 1 1/2 and 2 ton trucks ( my book is a 66). ,, The 3/4 ton diagram does not show it. They call it the "Ring gear thrust pad".

The book says run it up to the ring gear while rotating and then back off 1/12 of a turn for adjustment.
Does this sound correct????
Why do I have this on a 72 3/4 ton axle??
Dave