I just bought an old 1992 XJ, I took it out to test the 4x4, and it seemed to lock in and shift just fine including 4lo. But I started to crawl through a small ditch and the front wheels started to spin and the rear wheels were not turning, I backed out just fine and tried again in 4lo, and the same thing. I then shifted back to 2wd, and then the rear wheels would spin. I got the feeling that my 4x4 just meant front wheel drive. What's going on???