rear end noise

[texasz71]

hey guys new to the site and found lots of helpfull info maybe you can help with my problem i have a 99 half ton chevy silverado z71 i just replaced the rear diff with a factory gm locker and now i have a tapping or knocking sound around 30 mph i feel a little play in the drive shaft and to me it sounds like the transfer case but the 4wd works fine what could it be thanks for the help

[Jimmiee]

Best thing to do is to put the rear end on jack stands and have an assistant run it up to 30 mph.Get under there and pinpoint the noise. It could be anywhere under there but you wont know until you check it out.