I got my stock 3.23s replaced with yukon 4.10s a while back. As soon as I drove off from the shop, I had a very slight whirring noise throughout the RPM range with a howl from 40-45 or so, both on acceleration and deceleration. I took the truck back to the shop to tell them about the noise the weekend after I picked it up. (Got it on a Friday, went back Tuesday). They drove it, didn't crack the diff open to check anything, and told me the backlash and preload is fine, but the noise is likely because the pinion is spinning much faster than the stock one because of the numerically higher gearset. Anyway, this noise is driving me crazy, and I can't help but think its in some way damaging to my gearset. I changed the oil and the gears and pattern looked alright to me, but then again, I know nothing about gears. Are those guys at the shop feeding me BS or is everything okay? I simply don't know if I trust them after telling me everything was fine without looking at it. I wonder if anyone around the Baton Rouge area who has dealt with gears could give me a second opinion, I'm really not looking to spend anymore money on this, but don't want to have a major issue. Sorry for the life story, but thanks in advance.