I have a 1995 G20 Van. New axles, new bearings. But I get a loud noise from either the differential or tranny. Changes pitch at different speeds. Sounds kinda like howl or a low pitched siren. Any ideas what the issue is?

 

universals? have you checked them?

 

New universals, replaced driveshaft.

 

Everything is probably set a bit too tight. The gears should loosen up as they wear in. Make sure there is plenty of oil in the differential.

 

Noise can get very loud at times. Drowns out the radio at 45 mph.

 

It would be very hard to diagnose a noise over the computer as none of us can hear it and everyones description of noises is different. Does it only make the noise while on the gas pedal and go away when off? Find a safe place while it is making the noise put it in neutral, turn the engine off. Does it go away? Does it change at all when turning the steering wheel?

 

Yes, this is frustrating. Only makes the noise under power. When you let up on the gas and coast, it either goes away, or decreases.

 

I bet it is the tranny. You have a 4L80 I bet. Check the build sheet in the glove box and if there is a MXO I think that you have the 4L80 and it has a whine to it at low speeds.

 

Sounds like a bad pinion bearing

 

I suspected a pinion bearing, when the new axles and bearings were installed, the unit felt solid with no movement. And the differential was clean with no "junk".