Rear Differential Clutch Lock up

Andy Casperson · November 10

I have a 2023 Chevrolet 3500 DRW 6.6 Duramax, Crew Cab, 8' bed. 22,000 mi.

We pull a 35' 5th wheel. Approx 14k loaded. After a 3-4 hour pull, 55-65 mph., you pull off the highway, make a 45-90 degree turn, and the rear differential is locked up and chatters BAD.... I have had it to the dealership at 15k for howl, and the same chatter. They found metal and replaced EVERYTHING. Still doing this. Advised the dealer at Oil change. They didn't note any problems? I have read many a forum that advise switching gear oil to aftermarket HP Fluid. Any one have a solution?

Pryme · November 10

36 minutes ago, Andy Casperson said:

I have a 2023 Chevrolet 3500 DRW 6.6 Duramax, Crew Cab, 8' bed. 22,000 mi.

We pull a 35' 5th wheel. Approx 14k loaded. After a 3-4 hour pull, 55-65 mph., you pull off the highway, make a 45-90 degree turn, and the rear differential is locked up and chatters BAD.... I have had it to the dealership at 15k for howl, and the same chatter. They found metal and replaced EVERYTHING. Still doing this. Advised the dealer at Oil change. They didn't note any problems? I have read many a forum that advise switching gear oil to aftermarket HP Fluid. Any one have a solution?

Sorry to hear this. Did they let you know what the fluid level was originally? Most likely it was low since pretty much all of these trucks are low from the factory but not usually low enough to cause what happened to you so I wonder if yours was extremely low.
Hopefully you get to the bottom of it. They may have done something wrong on the rebuild.

Andy Casperson · November 10

Thanks Pryme! It was checked several times prior, they were quick to advise of the correct level is NOT at the fill plug level. (I questioned that) I questioned the forums that feel GM was not using a quality gear oil. They didn't agree. Just frustrated with it all. Spent close to $90K for a care free tow vehicle.

bruceb58 · November 10

34 minutes ago, Andy Casperson said:

Thanks Pryme! It was checked several times prior, they were quick to advise of the correct level is NOT at the fill plug level. (I questioned that) I questioned the forums that feel GM was not using a quality gear oil. They didn't agree. Just frustrated with it all. Spent close to $90K for a care free tow vehicle.

Level with the fill plug is an acceptable level. 0 to 10mm below the fill plug is the spec.

From the service manual: