Is it common for the diff to whine slightly on a Jeep Cherokee with 89000 miles on the clock. Thanks

Check your diff and transmission oil levels if ok then have the bearings on the diff checked

Could be the pinion gear ,,Has it been leaking rear end oil? How many miles on this?Probly over a 100k? its old enough for it to start wearing out.Try changeing the rear end oil use Lucas.

that sounds right

I have the same vehicle, with the same issue. I had put the car on a rack and lifted it to pin point the cause of the clunk when shifting from park to reverse or reverse to drive. I found that the front diff mounts were grenaded, meaning they needed to be replace bad. with these mounts being bad it was causing the front diff housing to slam the frame up and down when shifting from park or reverse to drive. this is pretty expensive to fix, your talking $160 in parts and $540 in labor. I also had the service 4WD warning display on my dash cluster, i had the code read. It came up as a bad solenoid in the rear diff. this is about $200 parts and labor to fix. Also, dont know how many miles are on your jeep but if you've ever sub-merged your axles under water or if your over 60,000 miles you need to replace your gear oil in the front diff, rear diff and transfer case. This is a little costly to have a mechanic do as well because you're supposed to use synthetic gear oil. For a shop to do it you're looking at $360.

no this is not common do you know how to check differecial oil if you can then do so it is probably low

defective pinion bearing?

whining from the rear end is usually associated with the differential i would have the oil checked first,as low oil is associated with diff whine

bad tires?put the back tires on the front.
check the brakes,i can not hear the noise pitch,so i am guessing.

likely pinion bearing or carrier bearings. They howl, characteristically, and the howl changes frequency with speed. Do check the u-joints first, though.