Was a bad day yesterday as I traveled 700 miles to visit my 92 yr. old mother I was there about a week and when I was returning home from pa. I had to pay a bill about 7 miles from my mothers house the ran fine and shifted thru the 4 speed auto. trans. smoothly, when I went to leave 5 min. later the car would not move at all in any gear it was almost like the driveshaft was unhooked but it did hold in park like it should. When I would put it in gear I could hear a little movement it seemed in the driveshaft but would not move an inch in forward or reverse. I checked the trans. fluid it was a little low I added a qt. but it made no change at all. I had to rent a u-haul truck and trailer and trailered it home because I have to go to work on Thurs. Does any one have any ideas as what could have happened and gave me no forewarning to leave me stranded? I still have the car on a trailer so I could take it to a trans. shop if needed. I do'nt know if I want to spend $2-3 grand to rebuild it. The car is an 85 (300)SD I think it has the 722.3 auto. trans. I heard some people talk about a nut that can work itself off at the rear of the trans. that would leave the driveshaft in limbo but I do'nt think it would hold in park like it does? I also heard people talk about a B-2 piston could that be my problem if so where is it and is it hard to change?