Ok so my dad has a 1993 GMC Rally Stx 1 ton 12 passenger van. It has a 350 mated to a 700r4. We bought it a few years ago and have been using it as a church van and a driver (when my 73 is down lol). A while back we noticed that the pan seal on the 700r4 was leaking. It got so bad that you would have to check and refill it every trip. So, one day being the adventuresome "mechanic" that i am i decided to take on the task of replacing the pan filter and gasket on the transmission. I got it all back together fine. Later that day it was raining and my front tire blew causing the back to hydro plane and i went over a curb and down a steep hill. after we get the spare mounted, among the horrid alignment issues (which were resolved) i noticed the transmission wouldn't hardly pull. I looked and the filter had fallen into the pan. So I got and reinstalled a new filter and made sure it was seated right. We got new tires and fixed the alignment. The transmission would shift, but it would slip a little into over drive. A few weeks ago I was driving it on the interstate and everything was going just fine. All of a sudden the engine started to free spin. I pulled off and figured out I only had first second and reverse. We checked the fluid and the level is ok and it looks ok and doesn't smell burnt. Does anyone know what could be wrong?