I have zero lockup on my 4L80e.

This is a swap into my 1968 Impala. I used a complete LY6 6.0 and trans from a low mile van. The ECM, TCM, motor and trans are all from the same van. The unit had 39K miles and was mint inside. I tore it apart to upgrade to a Jake's stage 3 kit which included 300m input shaft, billet hub, all new seals clutches, solenoids, wiring, and manifold. The trans shifts beautiful. I have all gears and works normal, just no lockup. The converter is a Yank PY3400 triple disk that was purchased new. The input shaft O-ring IS installed.

My dyno tuner says he was commanding lockup and everything looked OK on his end but it would not lock. It pops code P0894 when I drive at sustained higher speeds.

Before I tear it apart, what is the sequence for trouble shooting electrically?

I have checked these points so far.

Blue/white wire to brake switch-Ground when no brake- +12v when brake applied. I also did not work when it was floating no brake.

Confirmed the Blue/white wire goes to pin 9 X1 E38 ECM.
Confrimed the blue/white wire goes to pin 42 on the T42 TCM.
Confirmed less than one ohm measureing pin 9 to pin 42.
Confirmed brown wire on trans plus "S" goes to pin 1 on T42.

So, what is the next step. I am thinking ground trans plug "S" wire to see if I have lockup? I am lost and I am not really getting any support from my harness builder.

 

I ran a wire from trans "s" to ground. I can hear the solenoid inside the pan clicking and it draws enough current to spark but still did not lock the converter.

Any suggestions? At this point I assume it's mechanical issue? The converter was difficult to push on the last click due to the oring. Maybe it rolled or got cut. I just want to cover everything before I tear it apart.

 

I wanted to update this for future dum dums like me. Turns out I install the TCC apply valve backwards. Below shows how I installed it. The spring is supposed to go in first. I have not confirmed function yet but this is most likely the cause.

 

My lockup is now working.

 

Apologies in advance, but with this valve installed incorrectly would you be able to command lock up with scanner/HP Tuners?

 

Yes it was commanded in HP tuners. The ECM was commanding the whole time. I even bypassed it and hardwired it and I could hear the solenoid clicking. There is no pressure switch to tell the ECM the TCC is on, it only commands and compares input and output speed. At that point I knew it was not electrical.

The way I installed the valve the the TCC circuit was always exhausting and could not move to any other position.