d44 wheel locked up.

[67TEMP]

Yesterday I picked up a stock 87 xj with a d44 for $100. The owner said the brake was locked up or rusted on one side. Went to load it on the trailer and it was deffinatly locked, the xj wanted to go diagnol. When I got it off the trailer it drove normal in revers but going forward it would lock again. I pulled the driveshaft and it would drive straight enough for me to get it into the garage. I pulled the drum of the side that kept locking. With both rear tires off the ground I could turn the axle shaft, but when the other tire was on the ground it was locked. It wasn't locked like a locker would be. I drove it in a straight line for 400 feet and left a skid mark the entire time, so that wheel wasn't moving at all. Next thing I'm gonna do is pull the cover and see whats going on in the diff. I'm at work right now so anybody have any ideas where to start when I get back to working on it?

Thanks