My grandpa has a 98 cherokee green its clean the rear has a whining noise to it but the oil level is good is the rear bearings going bad it has a 118000 miles i think what is it worth it got a full tune up last year at 110000 miles so any one want to buy it.. It is currently off the road b.c he is cheap he doesnt like how much gas it waste.
Its possible the rear bearings are going bad, its hard to tell w/o driving it personally. Id say go for it but dont pay more then $2000 for it. I bought my 98 xj 4 years ago for $2200 and just recently parted it out before buying my wk.
Id say what ever is wrong with it is prolly an easy fix, but could be pinion or carrier bearings.
you don't have to swapped the axle out, rear bearings is an easy day job cost prolly hundo to do with new lube and seals and all. ide buy it but i already have one. 2000 on craigslist and i wouldn't give it more than a week without atleast a few looks.
my only reason to suggest swapping the axle out is to save money. If he does not have the know how to do a new bearing set he is better off cost wise to swap in a low mileage axle to save money. Typically its $500 plus to have a shop to a whole new bearing set on a rear end and you can get used rear ends like the 8.25 or the crappy D35 for sub $200 online. people give away the D35 rear end for $50 cause noone wants them cause they are junk.