epfatboy

iTrader: (3)

Want to run a 4L80E behind my L92/E38. What do I need to do to make this work?

Lots of searches come up with a T42 TCU and I can buy a harness but I'm not putting the pieces together. Like does the current 6L80e connector go to the T42 and the T42 to the 4L80e? I've seen some pictures of the TCU and it really doesn't tell a good story.
https://www.mrk-motorsports.com/stor...t42-tcm-4l80e/

Pretty sure I figured out what is needed in HPTuners but I'll take any tips I can get. I thought I'd flash in a tune from a Gen4 Express van which ran a L92/E38.

ryeguy2006a

iTrader: (27)

What program are you using for tuning? If you are working with HP Tuners, you can find a vehicle that ran a 4l80e that is compatible with your e38 ECU and do a segment swap so you can keep your current tune. This is assuming that the e38 ECU you have is what came with the L92.

epfatboy

iTrader: (3)

Thanks for the reply, the reading I was doing was getting me more confused!

yep HP tuners, I’ll look up what doing a segment swap is about.

my initial question is about the physical aspects for the harness and the TCM.

the E38 and L92 are a pair along with the harness. My plan is to cut down the harness and that’s when the light bulb went off. I wasn’t sure if I needed to splice in a 4l80e connector, then started reading about a TCM so I thought I’d ask some questions before I went much further.


I just completed a 4.8/4l80e build from a chevy express but it is a 24x. Thinking I should probably find a 58x version? I know e38’s run 4L80e’s in vans as well so I should be able to find a tune file.

toddrparr

this is the set up i am doing. My advice would be to find a prefabbed harness, Bp and PSI both make one that will mate the e38/t42 combo to a 4l80e. I did not do this... I took a harness from an 09 tahoe, 5.3/6l80 and modified it. It took a long time and required a lot of splices and new connectors. I did do it and so far it works, but it was a huge PIA and in hindsight I would buy a prefab. If you have questions on the process let me know.

67Skylark

I have a E38 and T42 controlling a 2009 LY6 and a 4L80E removed from an express van. I retained VVT and configured the hardware to match L92 (2010 Camaro with auto trans) I used PSI for harness and initial tune.. I believe what you are planning is possible.

ryeguy2006a

iTrader: (27)

Might be worth doing a cost benefit analysis for the modifications to your current harness with possibly adding modules and etc. vs selling it and buying Terminator X Max

epfatboy

iTrader: (3)

Yep! Last I checked the Dominator was the only unit with tranny control, thanks for tossing that out there I will be looking at it. Nice to have the Nitrous control built in as well, means I can also consider selling my external controller.

epfatboy

iTrader: (3)

I know this might sound weird but I don't mind carving up a harness, I actually enjoy the mindlessness of it as my day job kicks my brain in the *** regularly.

I'll PM you as I'm interested in knowing the pin outs and where you sourced your stuff from. I still consider myself a newb when it comes to EFI and I actually enjoy the learning process, as an example I was not aware the TCM was separate from the ECM.... My last build used a P59 and everything was integrated.

Minimally I can use what you have done to compare to the Terminator X mentioned by Ryeguy.

ryeguy2006a

iTrader: (27)

https://www.holley.com/products/fuel.../parts/550-918

Terminator X Max has transmission control. If you want to stick with the stock stuff I totally get it. But the adaptability and ease making adjustments is what I love about the the Holley ECU. There is also the Terminator X Max with trans control and DBW throttle body. And there are tons of vendors now that have Black Friday deals right now. Last year I bought mine from MCB and they gave me a great Black Friday deal.

epfatboy

iTrader: (3)

That's a price I can't argue with.... After a fair bit of reading and a call to Holley tech I'm going with the Holley unit. Really like the Nitrous control and if I ever decided to go Turbo I'll have that too.

Still curious on how to cut down a stock harness and convert it from a 6L80e to a 4L80e, feels like this is something alot of people did before Holley came out with a lower cost solution than the Dominator as the 6L isn't as stout as the 4L... not to mention availability and cost of the 4L!.

ryeguy2006a

iTrader: (27)

You won't be disappointed. Contact Andrew here if you want a remote tuning, he's a pro with the Holley EFI systems.

minytrker

iTrader: (13)

We install Holley on 99% of our builds. It’s an awesome system. If you have any questions just ask, we sell install and tune it everyday.

nicke

I have the exact setup you're trying to put together.

I am running an L92 with an E38 and T42 TCU, controlling my 4l80E. It all works flawlessly. I even kept VVT.
For wiring, I did a PSI harness so everything connected nicely.

Not sure what specific question you're asking, but seems like it is wiring related, Obviously the E38 gets wired to the T42 but let me know if I can help with specifics.

-Nick

Escot

Hey @epfatboy I realize this is an old thread & for some reason I can’t message people directly at the moment.

Did you ever get info on the 6l80e to 4l80e to allow you to re-work the 6l80e harness so that it’d work with your T42/4l80e combo?

Im in a similar situation where the 6.2 L92 I picked up was mated to a 6l80e (I only have the engine. Not the trans) and I wanted to mate the 6.2 to a 4l80 in my project. It seems like my options that I have readily available are to either try and figure out how to modify the 6l80e harness to work with the 4l80 and T42 or just use a gen3 harness I have with the addition of a 58x to 24x converter box.

Thanks

epfatboy

iTrader: (3)

So here is where I went and am…

bought the Holley term x max, easy peezee 4L80 support as well as other goodies like outputs and safeties until…

I had a warranty issue with Holley and sold it.

So the options were to go back to OEM and:

figure out how to re-pin the harness and run the E38/T42 which should not be hard
or
Roll everything out the door and build a Iron LS2…

Long story short I lost my Main bearings on the L92 and was dealing with a Holley warranty so I took the nuclear option and parted out the L92 and bought a LQ9 and some 799 heads and I’m running a P59 with my 4L80e.

I’ll do a 6.2 again at some point and use the E38/T42 option with a cut up harness as I know it works. I just didn’t have the experience needed at the time to make a decision I’d feel confident about… I think I do now so that’s all that matters!

Escot

Thanks for the quick reply @epfatboy.

Do you have any diagrams to share that I could refer to, to modify the gen4 harness (e38 pcm with 6l80e wiring) that came with my 6.2L to be compatible with a T42 module/4l80?

I’ve looked around but have only found a 6l80 trans. Connector pin out , and T42/4l60-65e pin out so far… which isn’t very telling

Like I said the other option I have, if I can’t make the gen4 harness I have work, which I think is my easiest route so far.. is to just use a gen3 stand alone harness that I made following LT1Swap and using that ligenfelter 58x to 24x module

epfatboy

iTrader: (3)

If you have what’s needed to get you from a 6L80e to a 4L60e the missing link is easy!

https://lt1swap.com/4l60e_4l80e_harness.htm

I see conversion harnesses that go from 6L80E to 4Lxxe, which is why I believe this was doable. I just haven’t got there yet.

dw456post

I started with a 2012 GM truck harness with a 6L80 plug. I bought a used 2008/09 truck harness with a 4L60 plug off the internet for 100 bucks. The 08/09 harness also has the T42 plug. I removed the wires for the 6L80 plug, got a subscription for Alldata for $20 and wired in the 4L60 and T42 plugs in the harness. Be sure and remove the pins undamaged so you can reuse them. You can use the 4L60 plug on the 4L80 trans---all you have to do is re pin the plug to a Gen 4 4L80 pin arrangement. There is a Gen 3 version that does not work. My E38 OS is 12653249 and is a 2012. The T42 OS is 2423356. Get an ISS pigtail and wire it in also.
I used the huge truck fuse box to get the car running and then ordered a BP Auto Fuse block to replace it.
You will need a separate brake switch to turn off TCC lockup if your vehicle does not have one.

Escot

Hey @dw456post , I'm not sure how to send PMs. I just wanted to make sure I'm understanding the info you shared correctly (I'm still not too familiar with gen4 ecm/tcm).

08/09 4l60e plug notes "Donor harness":
1) Find a 08/09 truck harness with a 4l60e plug (or, any gen4 harness with a 4l60e plug that I can will work, I assume. (ie. express van, etc.)
2) Pull the 4l60e and T42 module wiring out of the 08/09 harness
Then...
2012 harness with 6l80e plug notes:
1) Pull 6l80e wiring out of harness
2) Put 4l60e and T42 module wiring from donor into harness
3) Repin 4l60e plug to match Gen 4 4l80e pin arrangement
4) ISS Pigtail - What's this for? Sorry...

I'm still not certain I understand how to make sure that the E38 ecm OS and T42 tcm OS can be used with each other. I read that the OS for both have to match otherwise it will not work and I don't want to accidentally pull/buy a harness that doesnt work for my E38.

**EDIT: My E38 OS is 12605897

Thanks

dw456post

The 4L80 has two speed sensors on the top drivers side of the trans. The front one is ISS and the rear is VSS. Most late 4L60 trans have internal ISS sensors and do not have the external plug. Get on the internet and look for ISS pigtail for 4L80. Then you will have to wire it into the trans plug. I used an '09 plus (2012) E38 computer---it has the ability to use larger injectors--- I believe that I sent you the OS for the E38 and T42 on the last post ? A company called Auto 101 has E38's and T42's for sale and will program them with whatever OS that you need for cheap. Another question---Do you have HPTuners?
Another Option that you might want to consider is using a conversion harness (6L80 to 4L80) from PCM of NC. Kinda expensive, but it removes a LOT of work and rewiring that you will be doing.
When removing the 6L80 plug, there is a twisted pair of wires, tan and tan w/black stripe. Don't cut those, they are used to supply info to the DTC plug.
using a truck harness on a car, will require some patience and extending some wires to fit---depends on your project.
I probably have some notes on wiring if you decide to tackle this.
After I think about it, just get a new harness from BP auto and do it the easy way.