I'm looking at Crossfires and test drove 2 of them last weekend. The first was a 2004 with 35K miles on it. It's Chrysler certified, so it supposedly has been thoroughly checked. When I got out on the freeway I noticed the same thing that you are reporting. When I gave it gas at about 70+ mph I heard a pronounced whine from the rear end which got louder as the speed increased. When I let off it went away, so it clearly only did it when it was under a load. The salesman didn't have a clue, but I told him I thought it sounded like the powertrain. Their reaction is that it's certified so whatever is wrong will be fixed under warranty. I'm not that trusting. I drove a second Crossfire at another dealership that has about the same mileage on it. No sound of a whine at all.

All of that makes me wonder how frequently that happens. This is the first mention of that problem that I've found on this forum. Has anyone else out there had this same problem?