[f5fstop]

I have driven with the monsoon off to try and hear some of these strange noises the happen "on all" Hummers, and so far, no noise.
I'm 57, and I have learned throughout my many years, (last 14 in the car industry), never to believe what 80 percent of dealership service people say.
If they are not competent enough to fix a problem, there normal response is GM (or Ford, or whomever), cannot fix the problem and it is normal.
I cannot believe that someone at GM said that this is normal and they are not doing anything about it...IF it is as large of a problem as the dealer implies.
As an employee of GM, I can tell you, they have a quality push on that is driving many crazy.
As for the timing change, it is set to a particular specification, and if it rattled on the H3, it would rattle on the Colorado/Canyon, since it is the identical engine. Torque is torque to an engine.

I would recommend that the dealer pull out his chassis ears (a require tool), and drive around till he locates the problem, and then either confirms it is the timing chain or some other source.