When you get to it, put the rear up on jackstands, put it in N and see if you can rotate the drivehaft and listen.
Then remove the wheels, remove the rotors, and remove the rear of the driveshaft from the pinion. Then lift up on each axle to check for free-play. Rotate the pinion and feel for roughness. If you drop the diff fluid check for exessive shavings. Then look at all the gears inside for chips and discoloration.
Check the u-joints by hand. Observe the parking brakes inside the rotors.
On my truck there's a parking brake adjustment nut on a cable end about under the driver's side near the back of the cab. IDK about yours.
Also, check your truck's front wheel bearings. Jack up lower a-arm. wiggle the wheel with hands at the 6:00 & 12:00 positions...vigorously. Any play and the bearing is going. Rotate and feel for roughness.
Let us know what you find.
