Man, I've had a similar problem with mine for years. Every so often, my 4wd accuator (located under the battery) corrodes and is left not working properly. The car would say it was in 4wd, but is wasn't. Anyway, you should check that (as stated in an earlier post). You will probably need to just replace it and you will be good. I read a very good post on how to do that on this forum, but if you just take that battery out and (unfortunately) the plate that holds it. (I couldn't totally get my plate out and had to bend the rusty bastard). Anyway, there are like only 3 screws that hold it in. Just remove and replace. The tricky part is latching the wire in the actuator. Anyway, I bet that will fix your problem.