I recently changed from 3.73 rear end gears to 4.56 gears made by genuine gear company. Had a local mechanic do the work for me and he sounds very knowledgable, but when i got the truck i noticed the rear end humming when driving under light acceleration. Do aftermarket gears tend to hum because of the different ratio or strength, or do I have a problem? Anyone else have this issue:help:

Aftermarket gears should not hum, or vibrate once installed Correctly.
I would take it back down there and have them take a look at it but becareful not to drive it too much (could cause accelerated rear end wear)

I had the exact same problem with my 8.5" rear end that I installed in my cutlass. What usually happens is when you install rear gears they need to setup the spacing correctly for the ring and pinion. Sometimes if this is not setup correctly it will cause a vibration. Also if you have a positive pinion angle (instead of a negative angle) this will also cause a vibration requireing you to get adustable upper control arms. But i dont think thats the case since you didnt swap out the rear end, just the gears.

If they are humming, chances are they are not installed correctly. Get it looked at ASAP.

yup. is there any gear lube in there? that will make it howl.

Thanks for the help guys, i didn't think it was right--gonna get it re-chalked and checked. ---I love this site:ro)