I've read through 'engine mount' and 'motor mount' threads which discuss replacement because of visible mount damage or engine vibration when running. What I notice is an exaggerated shudder when shutting off the engine. Almost like it's finished at the urinal :p: I consider the engine quite smooth when idling, accelerating, etc. It's just that shudder when you turn back the key. It's one of those things that might be acceptable at 167K miles but I'd question it on a brand new truck. Is this normal with high compression engines?

Thanks,
Sixto
97 C2500 'burb 167K miles

just go under and look if the rubber is damaged

They don't look damaged. Passenger side is not quite 1/4" more compressed than driver side but I expect that as mounts age.

Sixto
97 C2500 'burb 167K miles

I would also check your harmonic balancer.

i'd go with what Green Machine suggested.... mine did the same thing and also had an annoying rattle...once i changed the harmonic balancer it all went away

yup green is right... mine did the same thing. another way to know if thats the problem is grab the belt and try to move it (WITH MOTOR OFF) if it moves its bad... also when you start it up does it make a realllly loud rattle noise then stops.....

You can also check your motor mounts by taking a pry bar and prying up on the motor by the mounts, if there is alot of movement then your mounts are wore out. I would suggest the Energy Suspension inserts.

Another motor mount test.

Make sure the parking brake is on.

Place the trans in drive and hold the brake down and touch the go pedal. The engine will flex a tad but it shouldn't be excessive. Do the same to check the other mount by putting the trans in reverse and holding the brake down.

You don't have to stomp the go pedal. Just bring the RPM up a tad bit.

If the mounts are bad the fan can hit the shroud, which will make a hell of a racket.