Anyone have any thoughts on this? I know I have the right ECM to control the 6L series Tranny module. Speartech can make me a harness. Do you guys think I would have issues with the other components in the truck? I have one of the last few Vortec MAX's made with the 4l70E tranny before they all went to 6L80's.

I wonder about the gear selector, and what gear positions are selectable on a 6 speed truck. Is there still only 4 positions not including P, R, or N. I also wonder if a tech2 scanner can reprogram the LAN system for the 6L90E or 6L80E. I am going FI on this truck and when the 4L70E goes I would like to upgrade to the 6 speed if I can work all of the bugs out.

 

Should be a bolt in swap since they now come with them and tune the ECM for the TCM.

Might have to buy a cluster and a tap shift gear shifter. Trans cooler???

 

A user on here MNC5 has done this swap. Send him a link to this thread.

 

Thanks for the input guys; I would really like to do this swap. I would not mind running the tranny in manual/tap shift mode all of the time if it saves a bunch of issues with wiring and BCM/LAN communication. Sort of like an old school stage 3 manual valve body setup. I have read that the 6 speed can be set up for hard wired TAP shift control. I could use a small shifter with a switch on each end to actuate the up and down commands.

 

If I had to do it again I would install a GMC Denali wiring harness and have Speartech figure out how to get the transfer case working. Or you could go with AWD

It's a fairly straight forward swap.

1. Tranny
2. Wiring Harness from a GM vehicle that runs the 6sp
3. You'll need to get the fuel pump assembly that goes with the VIN you used to order the wiring harness. (or check to see if its the same as yours)
4. The tranny cooler lines.
5. Flash with new OS from the VIN matching your wiring harness.
6. I've got a new shifter stalk but haven't installed it. Stock one works fine for leaving it in drive.
7. I tried a couple of times to order a new cluster and wasn't able to.

I'm still living without 4wd as I went with a 6L90e which uses a HD transfer case that was needed to match up to the 90's larger output shaft. Oh, and the wiring harness VIN I used didn't have electric fans so I did secondary work around to fix that. I've heard that the 09 VMax's come with the 6sp if thats true it would make your swap even easier.

Good Luck

 

Good info, I am 2WD so no need for transfer case issues. I know I can get the OS for a Vmax with a 4L80E, and yes you are right the late 08 and all 09 VMAX's have the 4L80E. Where did you get your harness? Was it a complete harness or just the tranny part? How did the tranny support work out? Do you still have your Trans temp display? And did the VSS from the tranny to the truck work out? But yes if I wanted I could order prob every part from a 09, cross support, trans cooler lines, Harness, etc. but I am unsure as to how the BCM will act to all of these changes. Are there any bugs in your set up? codes? speedo? Shift selector? What converter did you use, stock 4L70E?
LOL bunch of questions but any input is helpful.

 

did you have to change or modify the shift cable?

 

If the late 08's and 09's have a 4L80 its not going to help you. I'm assuming you meant 6L80e

To answer your ?'s

I'm running a modified stock cross member
Got the wiring harness from my local GM dealer
Tranny Temp does display
Speedo was on the money after a flash
Shift selector is limited to P R N D
I'm running a PI converter
If you get a new Trans from GM it will come with a Converter
The stock converter from your 4L70 won't work.
My set up has bugs, but only with the transfer case. No other codes
but my DIC flashes 4WD Errors...

 

No shift cable modifications necessary..

 

This is a tremendous help and inspiring.
Was the mods to the tranny cross support minor? I bet installing a new harness was no walk in the park. Or was it mostly plug and play in the motor and trans area? I was also told the 4L70's have a box for back up lights, ETC did your harness correct that also?