I have a 2004 Silverado Crew Z71 (282k miles). I have a couple of issues with a clunk! Under normal driving conditions, at 49mph it clunks before getting to 50 and above. I thought at first it may be the over drive. Happens when in tow mode also. When I am slowing down it sounds like the rear end is coming out. Aggravating!!I'm going to start by dropping the driveshaft and replacing the slip yoke.

 

Try greasing the slip yoke before replacing it.

 

Copy. Thanks for the reply.

 

Took the truck to my mechanic. He removed the rear drive shaft, greased the yoke good and replaced the u-joints. I told him to go ahead and replace them due to the mileage on the truck. However, at acceleration, when it hits about 50, CLUNK! and you can feel it when it hits. My mechanic seems to think that I the torque converter may be going bad.