98 4R70W no drive

[iraceitall]

I just bought a 98 EB, 5.0/4R70W, with a little trans problem. Vehicle has 202k, trans was rebuilt 30K ago. It will not take off in D (sometimes briefly, then it kicks out), but goes in R, 1, or 2. No codes for engine or trans, O/D light does not flash, but have ABS codes C1102 (accelerator sensor) and C1230 (rear speed sensor circuit fault) Fluid is clean and full.

I had it in the shop and tried powerbraking against D, it engaged, but then as I revved to 2000 rpm, it kicked out. I let off the gas, and it engaged again, hard.

Any ideas?

 

[iraceitall]

No fluid leaks, range switch is secure and wiring good, neutral start switch works properly, no bad fuses or wiring I could see either...

 

[V8BoatBuilder]

Could it be a linkage problem, where the trans selector is straddling N and D?

 

[iraceitall]

UPDATE: fixed it!

After about 6 hours of online searching and phone calls, I decided to check the main pressure regulator valve in the valvebody, since the OE one is prone to wear. Sure enough it had a big worn spot. I ordered a new valve (Sonnax 76948-09) and gaskets, and it's working great!