It all started months ago, when I was studying the electronics. On '98-up 4L80Es, the manual lever position sensor, or MLPS, has a 4-pin connector and a 7-pin connector. The outputs of the 4-pin in each forward gear of pins A matches & B are the mirror of the required solenoid inputs.

So it seems possible to eliminate any need for any PCM or any dash switches, just choose gears by working the shifter in the center console.

The 1-2 solenoid in 1st gear is on, MLPS pin A reads hi, or 12v
The 1-2 solenoid in 2nd gear is off, MPLS pin A reads lo, or 0v
The 1-2 solenoid in 3rd gear is off, MPLS pin A reads lo, or 0v
The 1-2 solenoid in 4th gear is on, MPLS pin A reads hi, or 12v

The 2-3 solenoid in 1st gear is off, MPLS pin B reads hi, or 12v
The 2-3 solenoid in 2nd gear is off, MPLS pin B reads hi, or 12v
The 2-3 solenoid in 3rd gear is on, MPLS pin B reads lo, or 0v
The 2-3 solenoid in 4th gear is off, MPLS pin B reads lo, or 0v

Now, to wire it up, is there a simpler solution to the mirroring than using relays? Because I'm planning to try it using relays to reverse the mirroring.

 

Shifts and application of clutches are not binary.
Timing of the release of one clutch before applying another is key. The modulation of how firm a shift is applied makes the difference between a car that's a pleasure to drive and a car that's just miserable. It is also the difference between clutches that fail early and those that last tens of thousands of miles.

Study the programming and tuning of a PCM tune and how the shifts are modified to be firmer. That's in addition to the base tune. A proper running auto that also shifts fast when it should is an opportunity to have the best of all worlds. On/off shifts is not.

 

So I'll need a delay? That seems doable. Maybe I should try Arduino after all?