at work we have a 1993 ford f150 2wd, the truck runs and drives good but the tred on the back tires are wearing on the inside instead of wearing evenly and going at slow speeds the rear end kind of makes a grindind noise and squeels like metal against metal, the rearend is full of fluid, the truck also has a 302 with automatic tranny and has 315653 miles on it, original motor and tranny, does the rearend have a bad bearing or could something else be causing this

 

Sounds like you're gonna need some kind of part replacement. As long as you dont live where it gets super cold, if it were mine, i'd drain the fluid and replace it 100% with lucas engine oil additive, I've used it many a time on squealers with no issue.

 

Sounds like bearing or bent axle. Need to jack it up and check for loose motion.