[eddielugnutz]

check fluid level first, then pull cover inspect fluid for obvious metal flakes glaze or debris and look for any obvious things. original rear i assume, problably haven't changed the fluid lately, maybe the bearings are going? inspect axles for wear, good time to replace seals at each end while your at it. If the rear is f%cked, year one makes a remanufactured complete year with gear ratios of your choice for under 800$, that beats cost of getting a rear rebuilt by most places, (at least by me in NY) a shop wanted 1,000$ to put in 3.73 gears and a new trac loc in my rear, and not replace anything else, the rear is so easy to do yourself, why pay anyone, I did it with a few jack stands all by myself in a slanted driveway, so anyone can do it!
If you can't afford the complete rear or a rebuild job, rears are cheap and plentiful by me in junkyards, dozens for under 300$ some out of wrecks with aftermarket gears, the guys usually pull them and save them on the side and try to get more money for them, obviously. use the tape trick to determine the ratio, easiest way in a junkyard without pulling covers and counting teeth, and if you don't have a code list on hand, there is a site that has the axle code list, I think it's slowgt.com, not sure.