When turning in parking lots or pulling out onto street sometimes i hear a snapping sound from left side rear end its a dually doesnt do it all the time but when it does i feel resistance and the a loud metal snap sound and it moves freely

 

I suspect the limited slip differential is busted or due for a lube change..

 

Im not a mechanic by no means but if i pull the diff cover what do i look for

 

Besides presence of lube and absence of chunks of metal...

First look in the glovebox for the RPO codes to see if its limited slip- G80

Most 3500's are..

I would first suggest that you park the vehicle on a flat level firm surface, concrete driveway is ideal. Block the front tires and lift both rear wheel off the ground, place jack stands under the rear axle to stabalize the vehicle.
Then spin one wheel by hand while observing the other side which ought to be spinning opposite direction and listen for any noise when doing so..

report back.. see if I cant locate a manual or better source of info with some instructions and/or pictures..

 

IIRC, the G80 is a locker type rear end, therefore doesnt require limited slip modifiers w/ axle lube.


FWIW.................

ASE-3, Module 6- Rear Axles see chapter 5 p 148..

Eaton Differentials Install Manual

video's ought to give you an idea of what to expect with the cover removed.. Good Luck