mvett6802

I just acquired a low-mileage 2008 Z51 6-speed. Beautiful car all around. But there's a curious clunking sound when I creep forward in 1st or rearward in reverse. It only occurs at creep speed - 1-2 mph - as you first engage the clutch, or when you let off on the gas. Under normal acceleration, no clunk. And no noise under deceleration at normal speeds. It drives great.

Is this normal or do I need to be concerned?

Boomer111

Could be loose rear axle nuts.

Common issue, do a search for it, easy fix.

Could even be tie rod ends being loose as well as the clutch packs.

Boomer111

I copied this from another thread: The two primary causes of a "thunk" sound from the rear are loose axle nuts and/or slippage of the posi packs in the differential. Simplest to check are the axle nuts. No need to pull the wheels....just remove the center cap & use a 33mm socket to check for looseness. If loose, you can tighten temporarily to 145 ft. lbs but the nuts are "one time" to torque & should be replaced. GM p/n 10257766....couple of bucks each at the dealer. Remove the rear wheels; clean the axle stub threads with a wire brush; apply Permatex Red to the threads; tighten the new nuts to 145 ft. lbs; allow to dry overnight. Remount the wheels & drive around to see if the noise is gone. If not, could be slippage in the diff. You don't list the year of your C6, but diff. fluid with insufficient friction modifier was used in some earlier C6's. Replacement fluid is GM p/n 88862624 Dexron LS 75W-90 gear oil. Drive the car to warm the diff. fluid; jack the rear; set jack stands; drain the old fluid; & refill. Important then to drive 8-10 low speed figure 8's to force new fluid into the posi clutch packs. Doing both these DIY fixes should get rid of all rear end noises.

This was posted by member DaveS

rhoyvald

with above and it could be as simple as the exhaust pipes hitting the frame or any other aftermarket equipment. Check to see if the tailpipes hit anything or if any of the pipes are loose.

mvett6802

Thank you all. I will bring my car, and your comments, to my trusted mechanic and have him check everything.

davidfarmer

should be easy to find on a lift if it's the "easy" stuff, exhaust, sway bar off to one side, axle nuts....

Jerry0

Just had exact problem with my 2005 6 speed.. as mentioned on many posts
i did what was recommended replaced/retorqued axel nuts also had rear diff service done.. no more noise like a brand new car
i had this done at Local chevy dealer,, they also replaced my gas cap and cleared code,,, total for everything parts and labor $200

hope this helps

mvett6802

It does. Thanks. I'm scheduling service accordingly.