Buck,
I'm not talking about body damage. But broken halfshafts, worn out idlers, etc., yes they will warranty those things, even when used off road, as long as you aren't running oversize tires or have made alterations that will affect these things. Go to a Hummer Club event sometime. AMG will have a parts trailer there and factory techs and they do replace things under warranty with full knowledge of how the vehicle was used that day.
Scot Smith
1994 HMC4, Locked
"They're right, Wider IS Better..."
Southern Axle & SteeringRemanufactured Driveline & Steering Parts for Hummers