1990 Chevy Suburban V2500
3.73 GM 9.5" Corporate - Non Limited Slip

Rear end whine started around 200,000 miles under throttle from 54mph to 61 mph. Ended up getting worse so I overhauled the rear end myself. My first rear end job, but I am a seasoned diesel Tech. (not that makes me the best rear end Tech, but I understand about paying attention to detail). New everthing. Carrier, Spiders, ring and pinion (Motive gear set), Timken bearings. Old parts needed replaced, bearings worn and pitting, carrier was loose with no preload on it. BUT----- It makes the same whine from 54mph to 61mph while on the throttle! And I also have a high HIGH pitch noise under decel. It is not very loud but you can here it. Both whines sound like Harmonics to me but I am not a gear expert. The noises are way better than before I overhauled it, but I am discouraged there is any noise at all with all new parts and me triple checking everything by the book during the overhaul. You can only hear the noise once the rear end warms up. (20-50 miles of driving). The pics are of the gear contact (black wearing off teeth) at 400 miles when I changed the oil. (Valvoline 80w90 full syn). What am I missing?

 

Sounds to me like contact area on the gear faces isn't right. Did you have to shim the bearings?

 

Yes. Set pinion depth. Started with .000 shims and ended up with .0065 worth of shims to get the teeth moved into the carrier. Tooth contact was centered on both sides and looked good to me. As you can see in the pictures I put with the posts, the contact is across the gear tooth decent. Shimmed the carrier for correct backlash. Like I said, the setup was by the book.

 

Wasn't questioning your setup, just posting my opinion. Thats based on all new parts. If you feel this is a problem, I'd suggest jack it up, pull rear housing, and use plasti guage to check for mesh.