Failing differential?

[Ajax MD]

A few times now, at very irregular times, I've heard and felt a grumbling from the front of my truck. I can also feel a resistance to forward motion.
At first, I thought the hub nut on the front passenger's side might be loosening but inspection shows that it's still tight and the wheel spins smoothly and has no abnormal movement or pivot.

Usually, if I put the truck in reverse for a few feet, and move forward again, the noise/feeling stops. When parked, rotating the front driveshaft by hand, seems to reveal a fair bit of slop but I'm not certain what is "normal."

- Is there a specific way to diagnose a Torsen differential for failure? (beyond metal in the gear oil)
- Could a transmission or truck shop rebuild a differential or is it better to just obtain a replacement?

 

[Retiredwarhorses]

Check/change diff gear oil, check the magnetic plug…its Also possible to have a sticking caliper piston, so check your rotors and pads too.

 

[TOBASH]

Have you tried opening the drain plug on the differential and inspecting your fluid? You can also get a $40 Borascope on Amazon and actually look inside at the gears through the drain and the fill portals.

EDIT - I posted after RWH. sorry if redundant. Love the idea of sticking brakes.