anyone else have similar occurrence(s) w/ their trans? my gt trans makes a low rumble noise below 1500 rpms. seems like it's stays in too high of a gear when cruising... car starts to shutter from it and you can hear and feel it in the car. and their is a clunk sound at times when the trans shifts... you can hear it echo in the cabin of the car like the rear wheels hit a pot hole in the road. is this normal for gm trans?

Doesn't sound normal...I know i have a "clunk" sound when shifting from park to drive, but that's about it....

Better take her in and have them look at it. I know a few folks said their tranny was low on fluid....

Sometimes mine is pretty rough but that's almost always as it's downshifting. Today, actually, it was fairly rough with some minor clunks during one stop. Most of the time, it's perfect and that may be why I notice when it isn't. But, the only time I hear any noises that would ever come close to causing concern is when shifting from drive to reverse or back. It isn't as quiet as I would like but I don't think it's an issue. Along those lines, I think occasionally I can cause a clunk by lifting off the throttle at an "awkward" time for the transmission where it continues to shift with the remaining inertia/energy from the engine. It seems to throw it into the next gear with no load, causing a mild clunk.

FWIW, I drove another G8 for a couple days while waiting for delivery of mine. The other G8 seemed to drive better and I don't remember noticing the same issues. There were some things I'm sure are different (addressed in a TSB) and perhaps all the clunkiness will be fixed with that particular issue. We'll see...