I just bought a 2006 LT3 with 33k on it. I just noticed the cruise control does something funny when going down a hill or coasting and the engine doesn't have to work to keep up to speed. The tachometer jumps up and down by about 200-300 RPM and the car kind of jerks front to back until the ground levels out again and then the RPMs are steady. Anyone ever had this? It's still certified so I may take it back to the dealer to check it out.

 

next time you think its going to do it- put the car in 3rd. (to take it out of overdrive).
and set cruise and head downhill. see if it does what you say...

Im thinking its going in and out of overdrive thus the jerking and RPM ups and downs

 

Sounds like a plan, and I think you're right. Is this something that is within spec or should it be smoother than that?

 

my monte carlo also does this no clue on what it might be...

 

Took it back to the dealer for multiple problems, leaking head gasket, failing power steering pump, and the cruise control issue. They had my car for over two weeks and were not able to replicate the issue. I note it was happening when the weather was warmer, now that it's cold it doesn't do it as much. I'm not sure if it's related to the weather, or maybe replacing the head gaskets did something, not sure.