I was under the trooper today and noticed the rear passenger wheel is soaked in oil. Not brake fluid. It's a 92 LS with the 3.2l DOHC, 4wd.

I can only assume it's from the rear end (Diff..?) but have no idea where to start for fixing it. Only the 1 wheel has anything on it. Any help?

I am a DIY'er but this is my first 4wd vehicle and I also have never messed with the rear end on anything so I'm lost.

 

If its gear lube on the rear wheel then you should be able to smell it, it doesnt smell like oil, maybe the wheel seal is bad on that side allowing gear lube to leak out under driving conditions. I would check the differential level immediately and top it off, that should keep the rear end from seizing up or being damaged in case the level is low. how much gear lube it takes to top off the differential will tell you alot,

 

maybe the Strut or Shock failed and blew the oil out of it. My dads 1994 Geo Tracker did that on the passenger side strut. Or you might have a leak in the brake lines.

 

sounds like the axle seal, this a pretty involved process to replace on this vehicle.
it is a fairly involve process to do.