Trannie Issues

I have a 1996 Ford Explorer XLT with 5.0 V8, and all wheel drive. I was driving it a couple of weeks back, and felt a bit of a lag when I went to accelerate, and a couple of minutes after that, the transmission acted as though it had gone out completely. I had only been driving it for about 20 minutes or so total, when this happened. I parked it and changed the transmission filter and fluid, and it worked for about another 15 miles, then did the same thing. I need to know if there are any transmission buffs out there that may have an idea, or several that may be the problem. Also if there are any resources out there where I might get a diagram of the all wheel drive transmission. Thanks in advance for any help given.