96 4l60e in limp mode.

Hello, I'm first time user. Got problems with my 4l60e in my 69 camaro.
I'm in limp mode, (no 1st or 4th). codes p1864, and po753. Tranny was just rebuilt with new bands, clutchs, solenoids, and wiring in tranny. Had this problem before rebuilding but only po753 code, so replaced solenoid (1-2 shift) cleaned valved body, and replaced pressure manifold switch and problem went away, but tranny was used and started slipping so we rebuilt, but now back to no 1st or 4th. Need help.

I had the same problem with my transmission, I found the sun shell reaction gear was defective. It is located at the rear of the transmission. It cost me 58. dollars, but a lot of time to repair.

Thanks,
SC