Hey guys. Just joined up. I heard this is the place to learn about computer tuning for the old TBI systems. Be warned, I haven't really ventured into this on my own yet, but I look forward to learning.

Here's my issue at the moment.

I have a 1995 Yukon with a 5.7L and a 4L60e. Four months ago, the trans lost third gear, so I decided to swap in a 4L80e. I did as much research as I could. Then I went for it.

I bought a used 4L80e off Craigslist. It's a 91-93 model, but it had the electronics updated somewhere along the way, so it has the newer plug. I had that trans rebuilt, so it doesn't have the Bosch Force Motors. It should basically act like the newer 94+ 4L80e's now. If you need specifics on what was put into it, I can get those.

Here we get to the dilemma. I had it swapped in, changed the wiring around, and had a custom chip burned by a reputable OBD1 Tuning garage. Now it's still in limp mode. I checked the DTC codes with TTS Datamaster, and almost every code for the transmission was showing.

I have a 16197247 ECM. I rewired the transmission according to these diagrams, sent to me by the tuning garage.

4L60e wiring:



4L80e wiring:




According to the above diagrams, 3 wires were moved. The Brown wire from ECM pin E11 was moved from pin "U" on the 4L60e wiring diagram, and put to pin "S" on the 4L80e wiring diagram.
The two wires from E10 and E2 in the ECM from the 4L60e diagram were moved to ECM pins F2 and F3 and were removed from the transmission plug (not used), and were spliced into the new Input Speed Sensor.


If you guys have any ideas or suggestions, I'm all ears. I used TTS Datamaster DM35x31, which is listed for the 94-95 5.7L trucks with a 4L80e. Do you think I should try using DM35xOD, which is for the 4L60e?

I'm at a loss as to what's gone wrong. I'm fairly certain it's either the ECM or the tune, because literally every DTC for the transmission was thrown, including some like "Solenoid B Stuck ON" and "Solenoid B Stuck OFF".



Thanks guys, I appreciate it. I'm starting to regret trying this swap, but I know it will be worth it if I can ever get this running right.