Howl in 4th?

[Map63Vette]

So this may be a little mix of 4 speed and / or rear end, but when I'm cruising along and drop the car into 4th it starts getting a little noisy. It only started after I put my new rear end in it, and while it sounds a lot like a rear end howl it only seems to do it in 4th. I can wind it a little higher in 3rd with no obvious noise, but the second I drop the car in 4th it starts howling. It only does it under load for what it's worth. Any ideas what it might be? I noticed with the rear end swap that the driveshaft now goes further into the tail secion than before, but I wouldn't think it would cause a problem since I can push it in further when the rear U joint is disconntected before it bottoms out.

 

[Double M]

Noise in all gears BUT 4th, with 4th being direct, would be a tranny problem. Noise in 4th would suggest a differential problem. In 4th gear, there is no load on the tranny, you could actually take all the gears out except for the input gear and the 3-4 syncro assembly and drive the car. The big hint is you said the diff. was re-done.

Hope this helps.

Russ.

 

[Map63Vette]

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.