I'm in the process of finishing a 4l60e/np246 to 4l80e/np261 swap on my 2004 1500. I have the transmission and transfer case in, ECU flashed, and transfer case controller (TCC) removed. The vehicle is driving and shifting fine, but I'm still getting the "Service 4wd" message on the cluster information display. I was under the impression that removing the TCC would prevent the message but apparently there's another step. I have yet to finish wiring the 4wd switch on the t-case to trigger the front axle disconnect and tell the ECU when in 4low.

I searched and couldn't find a solution to this, so I'm hoping someone has been through this before and solved the problem. Is this a BCM issue where it needs to be flashed?

 

Update: I stumbled across the solution this morning. The trick is to remove the TREC (transfer case encoder motor) fuse and then unhook the battery for 30-60 seconds. This causes the computer to forget that there ever was a TCC and thus doesn't look for it. On hooking the battery up, no move "Service 4wd" message.

 

Sweet! Sounds like a cool swap.

I've thought about swapping the NP246 in my suburban 2500 to a NP26X...the NP261 is a manual shift, right?

 

Yes. Basic old manual/floor shift transfer case. Nothing to die.

 

Very cool!

I'm interested in your truck. What configuration is it? What mods? 🤔

 

2004 Silverado 1500, 5.3 4x4, reg cab/short bed.

There's not much to tell. It's just a basic beater truck that I use to run around town. The rockers/fenders/etc are completely rusted out, I'm probably the 3rd or 4th owner, and there's no telling how it's been treated over its life.

The 4l60e scrapped itself this summer at 195k miles. I didn't want to waste the money on rebuilding the 4l60e, and I wasn't about to buy another used 4l60e. For me, the logical solution was to dig up a 4l80e from a wrecked truck and swap that. When I pulled the np246 (autotrac) apart to change the input shaft (to go behind the 4l80e), I found it was trashed as well (clutches were roasted, parts were worn out/broken, etc.), so again, not spending money on rebuilding junk. I hit up Crigslist and I picked up a np261 and factory floor shifter out of another GMT800 1500 for $150. The factory 1500/4l60e driveshafts didn't fit after the 4l80e swap, so I used the front driveshaft from a 2500 (4l80e truck) and the rear is from a 1999 tahoe 1500 4x4 (a bit shorter than ideal but it works).

I have no real plans of modding this thing, rather I'm just trying to have a reliable truck that I can drive until the end of time. Cheap, reliable, and easy to fix. I've got an 02 Duramax that I use as a tow vehicle and then I've got other toys (C5, C3, Jeep XJs, etc.) to mod.

 

Did you get the wiring sorted out? I’m doing the same swap. I have the diagrams from alldata only one that looks like an issue is circuit 1695 from the front diff going to EBCM then to pin 19 on PCM C2

 

You have to modify your electronic t-case harness to be a clone of a manual t-case wiring harness, so there's lots of wires you can remove and some that need to be spliced. Unplug the entire t-case harness and lay it out on the garage floor.

You need to find the wiring diagram for both the manual t-case and electronic t-case, lay them side by side, and then you should see exactly what has to be corrected.