I installed a set of GM 4.10s and a Torsen posi in my Formula. After about 50 miles, they are starting to whine under acceleration at about 40 mph. I used a solid crush collar and set the pinion preload to 25 in-lbs. Backlash was set to 0.008".
I'm thinking that I will remove the cover and recheck the backlash. If that is ok, then it has to be my pinion bearings, right? After 50 miles, do you think that the bearings are broken in? If so, my pinion preload should now be about 12 in-lbs, right?
All thoughts appreciated. Thanks,
Chris

 

without looking in a manual i'd guess your preload would be more in the 15-20 in/lb range

 

Ok, so I took the rear apart. The preload on the pinion was zero. That explained why the gears started to whine. I tried to tighten the pinion nut, but it was still very tight. The only way I can explain the loss of preload is that I didn't seat the bearing races fully. And as I was driving, the load on the races must have forced them fully into place, thus reducing the preload. I had to take 0.008 shim out to get back to 25 in-lbs of preload. Hopefully this will solve my problem.