Jeeps aren't GM products, but I can still help. Have you ever had the
transmission serviced? Chances are you haven't, and need to.
Hopefully you haven't damaged your trans to bad by driving it for too
long this way. Jeeps are known for bad rear ends, and transmission
trouble. The trans filter is probably full of garbage/plugged up. If
you did drive too long with it this way it will shift better after
installing a new filter and fluid, but the damage is done. Also, just
a heads up......if your rear end is making noise you better get that
looked at too. I put all new bearings in the rear of my 98 Grand
Cherokee limited to the tune of $360.00 my cost. I'm not sure what list
price was, but it is quite a bit more. I've always liked the looks of
the Grand Cherokee's, but beauty is only skin deep. It's the worst
vehicle I've ever owned.