i just put a new 12 bolt with 4.11 gears,new pinion,carrier,axle bearings and seals,arm-steal posi unit,moser alloy axles in my 71 chevelle. filled it up with oil and the posi oil and took it aroud the block and when i was de accelerating it would make a humming noise. sounded like some vibration, but i think it could be from the rear. is this noise common from 4.11 gears? everything is brand new. has anyone experienced weird noises with new rears b4? could i just need to break it in first? thanks alot for your help!

The only 'breakin' would be a few figure 8s in the parking lot to lube up the posi. Then a few heat cycles for the gears. Won't be any noise due to ratio. If you have the proper gear backlash and tooth pattern, it should be quiet.

sounds like a backlash issue to me. Good luck paul