Cruise Control

I have a 2004 Chevy Trailblazer. When the cruise control is engaged and I am on about a 4% downgrade, the vehicle starts jerking. This isn't the normal slowing sensation you get with all cruise controls. It is a steady jerking (Do not attempt to drink coffee) I have had it looked at by several techs but they never take it down the correct grades to really experience it and tell me its the normal braking. Has anyone else had this problem or know what it is? I drive 30,000 miles a year and am always using the CC and its quite irritating. I am getting desperate!

I've experienced the same thing with my '04. Trouble is, living in Phx., everything is flat. I only see it crop up on long trips where there are major terrain changes so I can't take it to the dealer for evaluation. I will be watching your thread closely.