700r4 trNs trouble. Only has 1st and reverse shift s to others at high rpm

[WIDESIDE72]

I have a 700r4 in my 72 stepside. The trans was rebuilt years ago then the truck it was in sat for a few years. When i swapped it into this truck i forgot to change the filter but checked the fluid several times. I had the tv cable adjusted correctly and it was operating correctly. A few weeks back i drove to a cruise night at the local Wendy's. when i went to leave it would not shift out of 1st. I checked the fluid again and it was about 2 qts low. I added fluid and it still wouldnt shift out of 1st. I changed the fluid and filter. There was some discoloration but no burnt smell. There was some grey in the pan (clutches) no metal. Iirc it had not been changed in 10k miles or so. I added a can of seafoam trans flush and drove the truck a few miles, drained the fluid only and refilled with fresh fluid. No change.

After i changed the fluid and filter the trans would shift up to third at hight rpm but no od. I checked the governor and it wasnt stuck and the gears werent stripped.

I am thinking the valve body is gummed up (?)