2012 GMC Sierra SCSB 4.3 to 6.2 Swap GMT-900 NNBS
 

I found this 60,000 mile 2012 SCSB at a local dealership. It was pretty much spotless. I instantly liked it.

So far, I put a 2" drop shackle on the rear, replaced the 17 steel wheels with 20" aluminum Yukon wheel, tinted the windows and installed an Alpine stereo system.

https://cimg4.ibsrv.net/gimg/www.per...79c8e93a6b.jpg
https://cimg5.ibsrv.net/gimg/www.per...dd494ffdc5.jpg

Next the real fun begins....
https://cimg9.ibsrv.net/gimg/www.per...6c38f1a86f.jpg
80k mile 6.2 L94 from an Escalade. It came with the harness, accessories and an E38 ECM. This engine was extremely clean inside. Had they told me it was a 20,000 mile engine, I would have believed it. Even the cam bearings looked like new which is odd for an LS based engine.

After deliberation and debate, I decided to swap in a 6L80 with it. I must tell you that swapping a V8 into a truck that came with a V6 is no quick trick. But, that's what I am going to do.
Here is what I know ( or, what I think I know....)
The engine looks to go in with just a motor mounts. The frame pads appear to be permanent and the same for V8 or V6
The transmission crossmember is different. (I have sourced one from the salvage yard)
The drive shaft is different (I will have a custom shaft made)
The v8 trucks come with a fuel pump control module. The v6 trucks do not. So, rather than get into that can of worms, I intend to just run an Aeromotive return system and turn off the FPCM in the tune.
I am getting the transmission cooler lines, shifter cable and linkage from a salvage yard.
The a/c lines, rad hoses and heater hoses are different, so they will be picked up from a salvage yard or auto parts store.
For exhaust, I intend to buy headers and a single 3.5" exhaust system.
The air intake system is different for the V8s. So, I will either use a factory air box from the salvage yard or an Air Raid aftermarket system.
The 6L80 has to be compatible with the E38 and tune. I can't just buy any 6L80 and plug it in. So, I am going to have one built and the builder will flash the internal TCM to match my ECM program.
I will be getting 2200 ish Circle D stall converter (I still want this thing to be a truck and do truck things. So, no 4000 stall and big camshaft.
The heads have been sent to Frankenstein to be ported and I designed a nice little VVT camshaft that will make torque from idle and rev out strong to 6500 RPM.
I am no tuner, so I have enlisted Dr. Tune Em' All to sort out the spaghetti and program the digitals.

The Challenges:

• The V6 truck has a 4L60. So, the instrument cluster reads PRND321 whereas the V8 trucks with the 6L80's cluster reads PRNDM. (So, perhaps swapping in a cluster from a V8 truck solves this? Not sure if it will work that easily.)
• The V8 trucks have a shifter with manual tap-shift buttons for manual shifting. The V6 trucks have a traditional manual shifter. (So, will a column swap solve this? Or, is there other wiring missing?)
• The V8 trucks have a fuel pump control module and a non-return fuel system. Because this is likely to turn into a can of worms with the body harness being different, I will just run an Aeromotive turn style fuel system and turn the FPCM off in the tune.
• The v6 had an e37 ecm. I am hoping that the e38 ecm talks to the body control module (BCM) with no problems.
• Flashes, tunes and compatibility..... As I understand, the ECM and TCM will have to be flashed to a matching year to communicate. So, perhaps we will flash the them for a 2012 Sierra 5.3/6L80 file? And, hopefully that will play nice with the BCM module. This is a scariest part for me because I just don't have any experience with the programming side of things. Save me Nate! :D

So, that is all I have for now.

You’re on the right track so far. It’s going to be a long haul but it will be worth it. Good luck, should be one bad ride when your done.

siiiiick

A little update:

I have decided to keep the 4L60 and not convert to a 6L80. This was a tough decision because I really wanted the superior performance of the 6 speed auto. However, a few things dissuaded me from the 6L80 swap. 1) Because the truck was a v-6 originally, it has no provisions to manually shift the forward gears once the selector is placed in M for manual. 2) Even if I replace the steering column with a column from a 6L80 equipped truck, it is a mystery whether or not the rest of the requisite wiring is in place to send the signal from the manual shifter. 3) None of the the late model wiring/programming guys that I was able to find could say if the BCM could be successfully reprogrammed to run the manual shift hardware from the 6L80 and most of the aftermarket companies I spoke to only deal with stand alone wiring solutions. Not combos integrated with the factory ECM/BCM/TCM and offered no insight. 4) There was a notable amount of uncertainty among rebuilders and trans suppliers around their confidence in a problem free swap. Most of them just seemed a little "spooky" to me. I needed a trans expert to say to me: Do this, this and this and you will be good. No worries. I did not get that.

So, I have chosen to just run with a built 4L60 from RPM transmissions. These trans have been around forever and this seems like a much less potential problematic direction once RPM works their magic. In order to make this work, I ordered a 2012 Silverado 4.8/4L60 wiring harness with ECM. It is the same E38 ECM that came with the L94 6.2 engine, but it was just $75 more to get the ECM with the wiring harness ($275), so I had them add that to the order in case the tuner preferred to have it. I could have had the 6.2 Escalade harness modified to eliminate the 6L80 and add in 4L60 wiring, but a factory harness just seemed like less chance for errors or issues.

I spoke a to a few wiring and programming experts on this and the most helpful was Brendan of LT1Swap"dot"com. He said using that harness and ECM in this truck should be near plug and play once the ECM is repr0grammed with the correct VIN and 6.2 tune.

If all goes well, this just leaves me with the fuel system. At this point, I am deciding between the Aeromotive Stealth GM truck drop in pump and matching regulator or the Deatschwerks DW400 return fuel system kit. I have always had excellent results with Aeromotive in the past, but I love that the Deatschwerks comes as a complete kit and they seam to have an excellent reputation.

One other item of interest is: since the 4L60 has a 3.06 first gear as opposed to the 6L80' 4.03 first gear, I will likely change the trucks 3.27 rear axle ratio to between a 3.73 to 4.10 rear ratio.

i am doing the same l94 swap as you but i am actually going with the 6l80e instead of the 4l60e.

where did you buy your engine harness, and how did you go about finding the right one ?

im having the same issue as people not knowing exactly how to get the tapshift working. Plenty of people have gotten the 6l80e to shift and work with the e38 ECM though, just no way to manually shift the transmission.

there is a wiring harness that runs along the steering column and connects to the shifter. 4speed style allegedly has 2 wires, and tap shift has 4 wires. I have seen somebody say that their 4l60e truck had the tap shift wires there already, so it is possible you could already have the steering column harness. Problem is that, even with the column harness, tapshift still won’t work so i’m not exactly sure on what would be the next step. maybe something to do with the BCM ?

really interested on how you go about the fuel pump hot wire kit, i’d rather tune out the FPCM and do a hotwire kit then run a relay jump to power the FPCM.

the problem i think i’m going to have is the tuning, flashing part

I don’t have much left just need to buy AC lines and a radiator and i’ll be done. GAP silicone coolant hoses are coming in sometime next month

That is the part I did not know. I have a steering column out of a 6L80 truck and an instrument cluster, I just don't know about the BCM and the body harness. Frankly, I just don't want to get knee deep in the swap only to find out I have problems that are not easily solved. This is not a "project" for me. This is my daily. I know the 6L80 is superior in every way, but I feel like the 6.2 with a built 4L60 with a 4.10 rear gear will be a fun setup for a daily. If it isn't enough, I will put a Whipple or a Maggie on it.

I have no made a decision on this yet, but I need to choose very soon. I have looked at the Deatschewerks returns system kit and the Aeromotive Stealth setup. I am also considering just doing a Walbro 255 in place of the stock pump with the factory in-tank regulator. I am just not sure how easy it would be to upgrade the factory pump sending unit assy with the Walbro.

The Max Trac 2/5 drop is finished. I am very pleased with it. The handling has improved dramatically over the OEM setup. Too bad there are no fast ratio steering racks out there. That would be a nice addition to the mods.

https://cimg5.ibsrv.net/gimg/www.per...ce6de5f527.jpg

I also installed an Alpine system in the truck with a 2000 watt 5-channel and a 10" sub behind the console. It is nice having all the Android Auto/Car Play features along with some killer sound.

I wanted to see the pics side by side now that the truck is lowered....

https://cimg5.ibsrv.net/gimg/www.per...8720aa3182.jpg
https://cimg6.ibsrv.net/gimg/www.per...a1d13f7704.jpg

UPDATE:

The RPM Level 6 4L60 is on the way.
The FTI 2600 stall is here
Sent my injectors in to Snake Eater for a clean and flow
The Airaid air intake tube is here
Motor mounts here
All coolant, a/c lines and power steering pressure side all here (sourced from salvage yard)

At this point, just waiting for the new fuel module to get here from Rock Auto, then it gets forwarded to Deatschwerks who will install their 340 pump into the module and send it back to me. It is the last piece of the puzzle.
Going to install the engine the last week of this month, so in 2 weeks.

Isn’t the factory stall close to that? Why didn’t you go with 3000-3400 ?