96 5.7 4l60e harness to 97 5.7 4l80e trans

[dj_97]

Okay guys. Got a 96 Yukon 4x4 4l60 5.7. I have a 97 k2500 I’m swapping the engine and wiring harness from the Yukon into the 2500. Does anyone know or have a picture of what wires need to be switched out, and is it just at the trans or is it at the ECM also? Looked all over and only find stuff for an LS! Looking to swap engine and harness this week and would love to have the info on which wires to switch/add!

 

[dj_97]

Also going to be using the factory black box, not switching to the 411. Truck doesn’t have one, so I’m gonna be ordering one refurbished and programmed to the VIN. The Yukon has one but no idea who could reprogram to the 4l80e.

 

[dj_97]

“97 2500 has the 4l80e” sorry forgot to include!!

 

[GoToGuy]

Have gotten the service manuals from here? All the info is there, diagrams color code a all. Your not keepng the 4l80 in the truck?

 

[dj_97]

Have gotten the service manuals from here? All the info is there, diagrams color code a all. Your not keepng the 4l80 in the truck?

I’m keeping and using the 80. The wiring harness in the truck been cut. I’m going to use the harness from the Yukon and it has a 4l60 so I know the wiring is different

 

[dj_97]

What would happen if I just used the black box from the Yukon with no tune for the 80?

 

[df2x4]

The "LS Stuff" you're finding, does it look like this? Scroll down to where it says "Wiring Conversion."

https://sites.google.com/site/sloppywiki/everything-ls/4l80e-info

If so half of it still applies as you're doing it at the transmission connector, and that didn't change. You remove two pins, move one, and leave the other out. The only thing that's different from the instructions there is the two pins/wires you have to add at the PCM for the input speed sensor on the 80E. Our PCMs are different, so those pins are in a different location. That info can be found in the factory service manual for your year as mentioned. We don't have the '96 GM factory service manuals archived here unfortunately so you'd have to find one somewhere else to verify. My '97 C1500 4.3L was pins 7 & 8 on the gray C3 connector but that may be different on a '96 V8 PCM.

If you don't want to mess with the transmission connector there are a few companies that make 60E to 80E conversion harnesses that take most of the work out of this. You still have to dismantle one of the PCM connectors to add the ISS wiring but the harness kits include the ISS pigtail with connector already installed.

https://www.mrk-motorsports.com/store/adapters/gm-4l60e-to-4l80e-transmission-conversion-harness/

And yes, you will need to have your PCM tuned to control the 80E.

 

[dj_97]

The "LS Stuff" you're finding, does it look like this? Scroll down to where it says "Wiring Conversion."

https://sites.google.com/site/sloppywiki/everything-ls/4l80e-info

If so half of it still applies as you're doing it at the transmission connector, and that didn't change. You remove two pins, move one, and leave the other out. The only thing that's different from the instructions there is the two pins/wires you have to add at the PCM for the input speed sensor on the 80E. Our PCMs are different, so those pins are in a different location. That info can be found in the factory service manual for your year as mentioned. We don't have the '96 GM factory service manuals archived here unfortunately so you'd have to find one somewhere else to verify. My '97 C1500 4.3L was pins 7 & 8 on the gray C3 connector but that may be different on a '96 V8 PCM.

If you don't want to mess with the transmission connector there are a few companies that make 60E to 80E conversion harnesses that take most of the work out of this. You still have to dismantle one of the PCM connectors to add the ISS wiring but the harness kits include the ISS pigtail with connector already installed.

https://www.mrk-motorsports.com/store/adapters/gm-4l60e-to-4l80e-transmission-conversion-harness/

And yes, you will need to have your PCM tuned to control the 80E.

Thanks brother. Would it even yard drive with the pcm if it isn’t tuned first? I’m having a hard time finding a affordable tune and having a real hard time finding a pcm. I’ve found a company who refurbishes them and programs them to the vin, just not sure if I trust it yet

 

[df2x4]

Would it even yard drive with the pcm if it isn’t tuned first?

That I don't know, sorry. My guess would be you'll probably have some sort of limp mode, AKA one forward gear. No idea though. I had Black Bear Performance tune a PCM for the 80E prior to my swap so I was ready for it. IIRC their tunes are around $300-$350. Which may seem like a lot, but they offer free alterations to the tune for life and finding someone who tunes the '96-'97 black box PCMs isn't easy.

 

[thegawd]

you will definitely be able to drive it in limp mode with the fuse pulled or the plug not plugged in. I cant remember what gear limp mode is in the 4l80e but yes it will move. I read somewhere exactly what happens when a 4l80e is controlled by a 4l60e ECM but I cant remember or find it but I'll keep looking.

Al