I have a TH350 and a Rear end setup from a 02 which has been completely rebuilt by a speed shop. Now even before the rear end was rebuilt I've always had this howling noise from the center/rear of the car. I've got the car up to speed then killed it in neutral and it does not make the noise. The noise is only present when I press the gas pedal and moving. I also replace all my U joints.Could it be trans related?

 

No

Sounds like pinion bearings

 

Pinion bearings or possibly the gears. If the rear end was rebuilt using the same gears, and you had the same noise before and after the rebuild then I would say the gears are bad.

 

Of course it also depends strongly on what "completely rebuilt" means... it's not like there's some universal "list" of what that consists of.

Sounds to me like if "completely rebuilt" didn't even AFFECT it, then someone's concept of "completely rebuilt", is VERY DIFFERENT from mine.

 

Well I mean the rear end was completely swapped out to freshly rebuilt one. Axle and all(Came from 02).. I really wanted disc in the rear. And before the swap I had the same tone "howl" as I do in the new one. I reused none of the parts from the old one.

 

It could be coming from the rear end, but I would look somewhere else if it's the same noise.