ORIGINAL: RPaulG87
Ah I see, it's just putting spacers basically to make ''less play'' with the differentials so they don't chew up if they skip or whatever. Do you think I should upgrade to say... GST differentials, or do you think the stock ones shimmed (though this truck was previously owned and I don't know how much he drove it) would be reliable enough?
Hold both axles so that they can't move and then try to rock the pinion gear gently back and forth. Takes some experience, but there should be very little slack. Different people have different methods or techniques concerning shimmimg. I just know that I was blowing ring and pinion gears until I shimmed them crunchy. Diffs with new gears can be broken in (out of the vehicle) using a drill.