Howl in 4th?

Hmm, I see what you mean by that. Wouldn't I expect to hear some noise in other gears though too? I can cruise at 30 mph in 3rd with no apparent noise, but if I drop it into 4th it becomes evident. It just seems weird that it's more heavily gear specific than speed or load, but it is pretty hard to deny what you said about 4th being direct drive. I guess I may have to move this question over to drivetrain.