found a parts truck

[mars2878]

I have a 1999 Suburban k1500 LT 5.7L 4l60e w/ the auto 4wd button t-case.
I have access to a 1999 k2500 ccsb 7.4L 4l80e manual t-case.

I already took the all the interior parts that I can use, I'm currently pulling the hydro boost system.

I'm thinking about pulling the spindles & ULA's along w/ the rearend to do the 8-lug conversion, which would essentially give me a 1500HD.

So here are my questions:
1 - I see that the front diff are different, not sure how, can I use mine w/o complications?
2 - would the 4l80e/241 swap be straight forward? obviously just a driveshaft from a properly outfitted burban or get it cut, cut hole in floor for the shifter. what about the wiring/ecu?

I have the full donor to play w/, just need to know to grab while I'm there.

Thanks in advance for your help

 

[df2x4]

- would the 4l80e/241 swap be straight forward? obviously just a driveshaft from a properly outfitted burban or get it cut, cut hole in floor for the shifter. what about the wiring/ecu?

You'll need a new front driveshaft as well being a 4WD. The wiring and PCM stuff is actually pretty simple. You'll need a tune for the PCM to run the 4L80E properly though. Here's my swap thread for my '97 C1500. A little different than what you're dealing with (2WD and 96-97 PCM instead of 4WD and 98+ PCM) but it should answer some questions.

https://www.gmt400.com/threads/97-c1500-4l60e-to-4l80e-swap.38819/

 

[454cid]

I'm thinking about pulling the spindles & ULA's along w/ the rearend to do the 8-lug conversion, which would essentially give me a 1500HD.

Um.... you're going to do what?

 

[Supercharged111]

I think 1 mount from the bigger diff lines up, the other 3 require fab. Grab the front driveshaft and trans and case may bolt up. Same formula as a diesel 1500.

 

[mars2878]

Um.... you're going to do what?

what do you mean?

my understanding is that a heavy half is just 8-lug axles & different springs, am I mistaken?
so I just need to swap out the rear axle, leaf springs, spindles & UCA's. As far as the front diff, my understanding is that the unit in the 2500 has beefier internals & may or may not use the same mounting points? I don't plan on doing anything 4wd related that would warrant a beefier front diff. If I have time, I may grab it anyways & compare/decide later as I only have a limited time to get what I want off of it & have to prioritize what I want/need before the donor goes to the great beyond.

 

[mars2878]

I think 1 mount from the bigger diff lines up, the other 3 require fab. Grab the front driveshaft and trans and case may bolt up. Same formula as a diesel 1500.

def grabbing the front driveshaft if I grab the tranny & t-case

 

[mars2878]

You'll need a new front driveshaft as well being a 4WD. The wiring and PCM stuff is actually pretty simple. You'll need a tune for the PCM to run the 4L80E properly though. Here's my swap thread for my '97 C1500. A little different than what you're dealing with (2WD and 96-97 PCM instead of 4WD and 98+ PCM) but it should answer some questions.

https://www.gmt400.com/threads/97-c1500-4l60e-to-4l80e-swap.38819/

I did read yours, thank you. I read several others as well, some leave more questions than answers, while also having a lot of conjecture.
I'm thinking that I'll grab the ecu out of the donor as well, its the same yr, w/ the wrong engine but correct tranny & t-case, that should be an easy fix for them. Or maybe I'll hit up the local guy who parts these trucks out, maybe he has one w/ the correct setup?

 

[df2x4]

I did read yours, thank you. I read several others as well, some leave more questions than answers, while also having a lot of conjecture.
I'm thinking that I'll grab the ecu out of the donor as well, its the same yr, w/ the wrong engine but correct tranny & t-case, that should be an easy fix for them. Or maybe I'll hit up the local guy who parts these trucks out, maybe he has one w/ the correct setup?

Keep in mind that unless the truck you grab the PCM from has the same rear end gears as yours your speedometer won't read correctly and your shift points will be off. Possibly some other little odds and ends too. That's why I suggested getting a custom tune on the PCM you already have. I'd imagine hunting down a PCM with your exact setup might be difficult. For me (being a V6 truck) it would have been impossible. I already had a tune from Black Bear though so they altered it for free.

As far as adding the input speed sensor to the PCM connector, if you don't have a factory service manual with the connector diagrams then I'd go ask for them at performancetrucks.net. That's what I did to verify what was in my FSMs and they were very helpful.