4L80e TCC Lockup Troubleshooting Steps-HELP!
Thread Starter
Joined: May 2006
Posts: 1,170
Likes: 8
From: NW Chicago Burbs
4L80e TCC Lockup Troubleshooting Steps-HELP! 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.
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.
Last edited by alocker; Oct 29, 2015 at 09:45 AM.
Thread Starter
Joined: May 2006
Posts: 1,170
Likes: 8
From: NW Chicago Burbs
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.
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.
Thread Starter
Joined: May 2006
Posts: 1,170
Likes: 8
From: NW Chicago Burbs
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.
Thread Starter
Joined: May 2006
Posts: 1,170
Likes: 8
From: NW Chicago Burbs
The way I installed the valve the the TCC circuit was always exhausting and could not move to any other position.
