Transmission Conversion Harness GMT800-GMT900

We offer two types of transmission harnesses.
Our GMT800 harness converts the 4L60e to a 4L80e trans.  

Our GMT900 harness converts the 4l60e to a 4L80e trans with the PRDL switch.

- GMT800

4L60e to 4L80e Conversion Harness

This harness allows you to swap your existing 4l60e to the 4l80e transmission in your 1999-2007 classic body style truck. This harness supplies all the electrical inputs/outputs which are required to make the transmission shift properly, with correct PCM calibration changes.

Instructions

The adapter harness with the transmission plug (Figure 1) goes from the main 4l60e harness to the transmission plug on the 4l80e.


The wiring harness that has the Input Speed Sensor connector (Figure 2) plugs into the Input Speed Sensor (ISS) located on the side, towards the front, of the 80e transmission.

The two wires on the other end of the harness will plug into the RED or GREEN connector on the PCM. The red wire goes into pin 22 and the blue wire goes into pin 23. You must make sure to disconnect the connector and remove the red retainer to ensure that the pins are fully seated.

 

*Please note that this harness is only the electrical part of the conversion. In order for the transmission to shift properly you must have your pcm reprogrammed.

- GMT900

Disassemble the TCM connector by removing the Blue TPA on the front side of the connector.  Remove the low signal wire from pin 45 and push it into location pin 26. Assembling the TCM connector requires attention!  Be sure all terminals are squared up and all terminals are fully pushed in before the blue tpa is pushed in.  Terminals can push out!

Disassemble the TCM connector by removing the Blue TPA on the front side of the connector.  Remove the low signal wire from pin 45 and push it into location pin 26. Assembling the TCM connector requires attention!  Be sure all terminals are squared up and all terminals are fully pushed in before the blue tpa is pushed in.  Terminals can push out!