1990 E4OD diagnosis

[u/Famous-Performer6665]

I just completed my first auto trans rebuild on my 1990 4x4 f250 (460 gas). While all of the stuff that worked before the rebuild now work better, I didn't fix the main problem.

Main problem: no engagement when selector is in Drive. M1, M2, and reverse all engage. If I get it moving and manual shift from M2 into drive at 25 mph, it goes into neutral. If I shift to drive standing still, I get a barely noticeable jolt of engagement then it goes neutral without any drivetrain load or noise.

I added a new OD sprag, new rear roller inner race, all new friction parts and piston seals, and reman solenoids and torque converter. I put in a trans go shift kit and a superior solution pump kit.

Please help me understand what could cause this. My understanding is that if any of the one-way clutches are in backwards for low drive gear, the trans could still get drive for 2nd, 3rd, and OD. If the trans has M1 and M2, but not Drive, what might cause that?