[wagonman76]

I have a service manual for my 92 Trans Sport van. The 3800/4T60E section may be very similar to yours. Don't have a functional scanner here so I'll do my best in words.

It says if the PWM is stuck open, TCC will not engage. Stuck closed and it will engage harsher. The regular 440T4 (which every other of my vehicles has) has no PWM, sure you can feel the engagement rather than the butter smooth engagement of the 4T60E, but it's not bad.

It also says that certain conditions must be met with the VSS, CTS, TPS, and by comparing engine speed and vehicle speed it is supposed to know what gear it is in.

The PWM should run at the same time as the TCC, but they are separately controlled. Here is what my book says regarding the transaxle connector.

Yellow/Black - Shift Solenoid B to ECM (ECM grounds it to energize solenoid)
Light Green - Shift Solenoid A to ECM (ECM grounds it to energize solenoid)
Tan/Black - TCC Apply Solenoid to ECM (ECM grounds it to energize solenoid)
White - TCC PWM Solenoid to ECM (ECM grounds it to energize solenoid)
Pink/White - 12v+ w/ignition (powers Shift A, Shift B, and PWM solenoids)
Purple - TCC Brake Input (12v+ w/ignition, sends 12V+ w/ignition into this wire to ECM and to TCC solenoid, cuts power when brake pedal is pressed)
A 7th wire is not used and may or may not exist, it is for temperature sensing on the higher powered models (3.4 DOHC, Caddy V8, maybe 3800SC)

Shift Solenoid A - 20 ohms
Shift Solenoid B - 20 ohms
TCC Solenoid - 20 ohms
PWM Solenoid - 10 ohms

1st gear - A energized, B energized
2nd gear - A open, B energized
3rd gear - A open, B open
4th gear - A energized, B open

What I would do is cut the wires to the solenoids. On the trans end use your homemade shift box. On the car end I would wire in the appropriate resistor to make the ECM think it is running the solenoid. Just leave the PWM wire disconnected on the trans end, and it should keep it full power, but connect it through a 10 ohm resistor on the car end to make it think it is still there. Seems intuitively backwards for the PWM, but the book says open (no engage) is 100% duty cycle (I would think means full power) and closed (harsh engage) is 0% duty cycle (I would think means no power).

It still might get discrepancies since it compares vehicle speed and engine speed with what gear it thinks it should be in. Hopefully it does not throw a code, but if it does it will be easy to go back to where you were. Or if the code does not affect mileage or driveability, leave it.