99 Tahoe Clunk and Jerk When Engine Starts

[99tahoesnk]

Hi Fellow Tahoe Owners,Hope someone has an answer for me! My Tahoe is a '99 two door , two wheel drive with 5.7 and auto transmission.The first problem I have occurs the instant the engine fires up. It does not happen every time, but is becoming more frequent.It usually occurs only the first time it is started each morning.It will sometimes do it later in the day if it has not been run for several hours.This happens in PARK,with or without the parking brake set and with or without my foot on the brake pedal. As soon as the engine fires you can feel the Tahoe jerk as if it wants to back up. In that same instant there is a sound similar to a hammer striking a piece of steel. In just a fraction of a second it is all over and it runs just fine.The second part of the problem is that SOMETIMES when I shift from drive to park. it makes a sharp clang noise as the lever goes to park, BUT, there is NO jerking motion.Any ideas? Thanks, SNK

[MIkeman28]

wow, very odd. I know when Im on an uphill or driveway, and put in reverse, it will make a little clunk. But thats because the tranny is under pressure before it engages into gear.

Never heard of a truck jerking to the point that it feels like its going to go in reverse while in park! Something is trying to engage. Try to have someone outside listening to exactly where the noise is coming from so you can narrow down the possibilities.