Retrofit TOW/HAUL switch for 4L80e?

[DA BIG ONE]

Been reading there is a factory tow/haul option on newer 4L80e transmissions, so, does anyone know how to install one into a 1999 4L80e?

Right now I run 33" tires + 3.42 gears w/tranny in 3rd gear up 65+ mph lockup only comes in @ 60mph with my setup. This gives me almost same rpm range as I had w/30" tires, 4.10 gears in 4th.

I'm hoping tow/haul setup locks converter sooner.

[DennisG01]

I don't the answer, but I'll be interested to find out.

Some thoughts:

1) Is the tranny controlled by the main ECM, or is there a separate computer for tranny functions?

2) Could Kennedy or Wester's write a new program for the computer to mimic/improve upon what the current GM tow/haul program does?

[DA BIG ONE]

I don't the answer, but I'll be interested to find out.

Some thoughts:

1) Is the tranny controlled by the main ECM, or is there a separate computer for tranny functions?

2) Could Kennedy or Wester's write a new program for the computer to mimic/improve upon what the current GM tow/haul program does?


It is my understanding that the newer ecm overrides attempts to lock tc by aftermarket kits designed to do this.

I have an aftermarket performance re-right and requested transmission control to be left stock because of a high-end trans build and the use of TransGO HD2 shift reprogramming kit. The factory tow/hall feature should work on my 4L80e in my 99 burb, and I want to give it a try.

[DA BIG ONE]

Any of you know if this tow/haul option requires a flash. or?

[joed]

Do you have access to trans. wiring diagrams for the 99 and newer trucks with the tow haul feature?

If so, you could probably figure out what circuit gets grounded or turned on when the tow/haul switch is activated. I suspect the switch grounds the circuit.

You may be able to add a switch to accomplish this, and not have to modify the PCM.

Just a thought.

Joe.

[DennisG01]

Just thinking out loud here (well, it's out loud for me - for you guys it's probably rather silent;) )

I would venture a guess that the ECM would have to be re-flashed since activating the tow/haul mode causes a few things to take place, including changing the shift points/holding a gear longer. Sort of like: Normally you're in "drive mode" and when you push a button, it activates an entirely new program/set of parameters called "tow mode".

Maybe if Kennedy is hanging around, he can enlighten us on this. Especially since he now does all of his ECM flashing in-house. I can only imagine that this would be on the upper end of the technical difficulty scale.