Zero up shifting

I recently swapped transmissions in my 91 that has the A340H transmission. I had to change it because it had a bad front support bushing/seal that caused a huge leak into the transfer case, then eventually out of the vent plug. I got the new trans in but now when test driving it won’t shift out of first. I have done the following:

Changed solenoids
Changed Valve bodies
Checked linkage
Checked shifting selector
Changed kickdown cable

None of that has fixed my problem. My question is, what controls the transmission shifting? I know the solenoids get energized and then it shifts, but what gets a signal and makes the choice to energize the solenoids based off the inputs? Does the speed sensor (not the aft sensor but the one towards the middle) control shifting? My next move is to check the TPS and ensure that is reading the correct voltage based on throttle input. Any other ideas? Along with the TPS I’m going to perform the manual shift test. Given the results that my issue is electrical and not mechanical, what should I turn to first? I’m really growing tired of this trans issue.

Also, does anyone know the pins on the ECU that the two speed sensor wires go to? I want to wire the sensor directly to the ECU and bypass my transmission harness in a troubleshooting effort. Any help, tips, tricks, advice, or even jokes at this point are greatly appreciated.

 

UPDATE: I did the manual shift test and it passed so now I know my problem is electrical. I’m trying to troubleshoot wiring but I have this larger plug with six pins that has two wires coming out with a smaller plug. Where does the smaller plug go? I have a feeling this smaller plug goes to something that provides a signal that pertains to shifting.

 

FINALLY!!!!

It’s shifting now. The little plug pictured above plugs into a plug that was just hiding out on top of the transmission out of sight. What a headache this thing has been.

 

Score one for the persistent!

Never quit