I have a 1991 Chevy G20 Van with a 700R4 transmission, the initial problem was the transmission was slipping, then got to the point where it would not up shift at all and the van could not go any faster than 15 mph. I pulled the tranny and did a fresh rebuild on it with all new steals and friction's and seals. now I have no reverse, no speedometer and it is still acting the same way it did before the rebuild, not up shifting and can't do more than 15 mph. does anyone have any idea what could be wrong, this is my first transmission rebuild.

Thank you for your time

might have low oil pressure-when you did the rebuild,what was the condition of the original bands and frictions and was any unusual debris found in the pan.

No nothing unusual in the pan, the band was worn a bit with a few cracks, most of the frictions were burnt steels seemed ok only a couple had heat marks. all the gears races all other parts had no heat marks and looked normal and no play in any of the planetary gears and there did not seem to be any wear on the gears either.

UPDATE, I found my problem, It was the electric up-shift solenoid that goes into the pump. I replaced it and bingo everything started working properly except for the speedometer and odometer. I put a new speed sensor in and it still is not working so if anyone has any ideas on that please let me know thank you very much.

Update#2, I found the speedometer problem, the press-fit speed sensor gear wasn't so much press-fit it had actually moved up the tail shaft and away from the sensor. I got it re-positioned and all is working fine. I used two aluminum ring-clamps to keep the gear in place.
Thank you all for your help it is greatly appreciated.