It never ceases to amaze me the amount of major work people will do without even looking at the FSM.

Right out of the 65 FSM, adjusting your axle end play, though that's probably not the only issue. Sounds like yout pinion to ring gear pattern is off. That would also b ein the FSM with pictures of what is good and what is not good.

axle.JPG
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.