So my 91 z28 has the dreaded bucking that seems to be pretty common with these cars. I have kind of figured out how to keep it from doing it, but I would rather just fix it and not have it cause me probs later. This car has been a work in progress for over a year, everything in the engine compartment (even a rebuilt 305) is new except for the MAP, which will get replaced sometime, and I have replaced the tranny fluid, pinion yoke seal because it was leaking, differential fluid and cover gasket, and it still has that damn buck! I'm gonna replace the fuel filter when it gets warmer outside, because it almost seems like a miss. When I replaced the pinion yoke seal, I was warned not to tighten the retaining nut more than it already was, so I counted the threads that were exposed and put it back together with the same number showing. I drove it around with an aweful wine when decelerating, so I tightened the nut just a hair and it solved it. But when I did this, I grabbed the whole pinion assembled and shook it a little bit to see if it was loose, and the damn thing will shimmy back and forth! I was told that I need to replace the pinion yoke bearing and that it was really simple, but this was from a ford guy and I don't tend to trust them Any ideas?

 

It's kinda late now, but before you removed your pinion nut you wanted to make a scribe mark on the nut and pinion shaft, then count the number of turns to get the nut off. Then when putting the nut back on, count the number of turns again till the marks line up. After that, you turn the nut 1/16th of a turn tighter to compensate for bearing and/or crush collar wear. You can use loctite or stake the threads to lock the nut in place. That's the shade-tree method. You might think you have it where it was, but it might not be.
If you plan on replacing the bearing, you have to disassemble the differential to replace the race and the crush collar as well. Then you might as well replace the other bearings too. You would then be at a place where you really need to know what you're doing for setting up proper bearing pre-load, or you could end up with some premature bearing failure down the road.