What is the purpose of the crush collar in the rear end, just to help with preload? also, is a solid spacer better in any way than a crush collar?

 

the crush collar is there to get the right pinion depth. And a solid pinion spacer is way better than a crush collar.

 

Both the crush collar, and solid pinion spacer is there to keep the pinion tight. (It wouldn't normally take a few hundred ft lbs to get the correct preload on the bearings).

I don't use either. I set bearing preload, then tack weld the pinion nut to the gear.

 

Ding, Ding, Ding! The right answer is INTMD8! I haven't done the tack weld deal yet but it certainly should work just fine (just makes disassembly a little more of a pain.)

Steve