hello, I have a 2004 trailblazer (28K miles) which periodically groans, shudders and almost dies when in AWD or 4WD-HI, especially when pulling into a parking spot or turning a corner and other times when driving at slow speeds. It's been doing this off and on for about 2 years now and I've taken it to the dealer to check out 3 times. The first time it was an electrical issue with the 4WD switch. After fixing that it was good for about a year before the issue came back. The second time they couldn't find a problem and it never made noise or shuddered for them when they drove it. The third time I made sure to the engine was warm and that it was acting up immediately before bringing it in. Finally they noticed it, but this time said there was nothing wrong. They said it's common for the the AWD and 4WD to groan and shudder when driving on dry pavement. I don't make a habit of leaving the 4WD on when on dry pavement, but sometimes if I'm off-road, then going back to pavement I don't immediately remember to switch back to 2WD. During the winter when there is snow and ice I use the 4WD a lot and have noticed the groaning/shuddering then as well. That's not dry pavement! When I mentioned this they gave me a round about answer regarding the way the gears mesh and blah, blah blah. They basically stepped around it. I should also mention that the "check 4WD" light was coming on every now and then before bringing it in this third time. They said it was some faulty error code and it was re-set and shouldn't come back on again. I'm no expert, but this issue being normal doesn't seem right. Has anyone else had this problem? thanks!