2000 K2500 8.1 Swap

[obsk yesing97]

Once I get a 3500hd I’ll take pictures and upload all the information and differences I find between the two. I found one a few hours away, $2k and still had a hydraulic flatbed on it. Hoping to make this thread the all-in-one swap info for the 8.1, I love all the info that’s already on here, but it’d be much better if it was in one place and not spread across 50+ links. I’m debating on finding a website or social media specific for my truck, where I can upload documents and full information for each component I plan on swapping into the truck.

Also good to know that the 01-02 are 0411 PCM’s, means I can get a factory tune. Even the parts department and owner are having issues finding information on these trucks, and I work at a GM dealer. Getting ahold of the corporate information line next week, hoping they can send me links to find all the info and part numbers I need.

Please give us any and all information you find

 

[someotherguy]

Please give us any and all information you find

Really no big mystery to the swap. The 2001-2002 3500HD's are simply GMT400's (GMT455's technically) with the 8.1. You would essentially swap everything to your project truck. Engine, PCM, harness, etc. All the little stuff like the TAC module (gas pedal, assuming these are DBW), air filter setup, those things. You'd need to source a different transmission as the 3500HD will have the extended tailshaft with drum parking brake on the back, IMO might be tricky to fit under a lighter truck. But, a year-compatible 4L80E from a 2500-3500 should be trivial to swap in place. You'll have exhaust work, driveshaft work, and whatever other wiring challenges you might face if you're trying to swap this whole works into an older (for example, OBD-1 truck.)

I'm surprised to see OP's comment "Even the parts department and owner are having issues finding information on these trucks" - just go online and find one for sale that lists the VIN and punch that into your parts lookup. Here's pics of two I dug up many years ago that the VIN is legible; a 2001 and 2002. Hope they help:

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I see OP needed a bit more info as initially he was planning to source the engine from a GMT800 so the accessory drive and supporting parts will be completely different. It probably goes without saying that the "easiest" route for this swap is to start with a 2001-2002 3500HD donor, instead of getting the engine from a GMT800.

Richard

 

[obsk yesing97]

Really no big mystery to the swap. The 2001-2002 3500HD's are simply GMT400's (GMT455's technically) with the 8.1. You would essentially swap everything to your project truck. Engine, PCM, harness, etc. All the little stuff like the TAC module (gas pedal, assuming these are DBW), air filter setup, those things. You'd need to source a different transmission as the 3500HD will have the extended tailshaft with drum parking brake on the back, IMO might be tricky to fit under a lighter truck. But, a year-compatible 4L80E from a 2500-3500 should be trivial to swap in place. You'll have exhaust work, driveshaft work, and whatever other wiring challenges you might face if you're trying to swap this whole works into an older (for example, OBD-1 truck.)

I'm surprised to see OP's comment "Even the parts department and owner are having issues finding information on these trucks" - just go online and find one for sale that lists the VIN and punch that into your parts lookup. Here's pics of two I dug up many years ago that the VIN is legible; a 2001 and 2002. Hope they help:

You must be registered for see images attach

You must be registered for see images attach

I see OP needed a bit more info as initially he was planning to source the engine from a GMT800 so the accessory drive and supporting parts will be completely different. It probably goes without saying that the "easiest" route for this swap is to start with a 2001-2002 3500HD donor, instead of getting the engine from a GMT800.

Richard

Engine is bolted in my truck just need wiring help

 

[takingadip]

Engine is bolted in my truck just need wiring help

I solved the wiring issue by buying the whole donor truck 01-02 GMT455 w/8.1L and transferring the whole dash assembly with harness included. My truck originally came with the 5.7L and now has the 8.1L. I wasnt originally going to do that but I found the pinouts on the 5.7 vs 8.1 through wall connectors were different and did not want to hack apart the harness to make it work.

 

[L31MaxExpress]

I solved the wiring issue by buying the whole donor truck 01-02 GMT455 w/8.1L and transferring the whole dash assembly with harness included. My truck originally came with the 5.7L and now has the 8.1L. I wasnt originally going to do that but I found the pinouts on the 5.7 vs 8.1 through wall connectors were different and did not want to hack apart the harness to make it work.

I used the 8.1L van engine harness, removed what I needed to make it standalone, then tied it into the factory underhood fuse block and C100 connector using the rest of the factory 5.7L wiring on my 99 Tahoe.