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1999 Tahoe transmission

Last year I replaced the automatic transmission in my 1999 Tahoe at a local Chevy dealer. When I got the truck back, everything seemed fine except for a dull " clunk" sound when I first accelerated from a stop, and when I decelerated right before the truck stopped. I didn’t hear or feel the “clunk” when

the truck shifted once it was going.

I took it back to the dealer and they said it was not the new transmission that was causing the problem, and that it was the old rear end parts behind the transmission that needed to be replaced.

My questions are: Does their assessment make sense? What “parts behind the transmission” might cause the problem? And finally, where should I go for another diagnostic opinion?

GM lables driveline clunk as a combination of required clearences in several systems. In most cases it is anoying and not a longevity or reliability issue.

I conclude the obvious worn or about to fall off part possibility has been eliminated.

The u-joints on these and the Suburban and Yukon wear like most but are hard to diagnose with the driveshaft hooked up.

My '02 Tahoe had a ‘clunk’ when shifting into reverse and I suspected a worn u-joint.

I crawled under the truck with the wheels chocked and the tranny in nuetral with the parking brake off.

I tried to move the joint up and down and sideways to no avail. (Mine were tight and dry on the outside but found the rear one was dry but blue inside)

Then I got on the net and after a couple of searches found that others had come across the same problem and the method needed was to remove the driveshaft to actually see which u-joint was bad.

In all the different posts the answer was the same: remove the driveshaft.