whistling sound

[Va2500HD]

I have a whistling sound that I thought was originally coming from the engine compartment but it is really coming from the back half of the truck. It is most noticeable when completely letting off the accelerator at 45-60 mph. When letting off the acc. it sounds like a turbine winding down. But as soon as I touch the acc. it goes away instantly. The noise level is not real loud and can be drowned out by the radio. Any ideas?

[Va2500HD]

Let me add it's an 02 w/ 6.0 and 4.10. Should not be much in the back half of the truck that it's coming from, drivetrain or fuel system right? Is the fuel pump in the tank?

[GM-Tech]

Sounds like a classic case of a ring and pinion noise.

[Va2500HD]

Thx GM-Tech. I am not familiar with the "classic case". I will search and see what I can find under ring and pinion.

[Va2500HD]

Can anybody tell me about the "classic case" of ring and pinion noise? I've tried to search but can't open topics of search as my computer keeps giving me fatal error messages. thx

[GM-Tech]

Don't get stuck on the "classic case" comment.

 

Ring and pinions typically make their loudest whine around 45-55 mph or so. 45 seems to be the peak. They will also whine in only one direction usually... that is on accel but not decel or on float/coast but no accel or decel.