GMT 900 HD Body Swap

[LML Duramax 95 Z71]

I've been toying with the idea of swapping a GMT400 body, specifically an ext cab long bed body on to a GMT900 HD+ chassis. Now I know the idea sounds crazy at first but I've done a little research and the wheelbase of a double cab 6.6ft box on the new truck is only 2 inches longer than the 400. So in theory besides punching new body mount and bumper mount holes, the swap shouldn't be too hard right? If I'm missing anything please do point it out to me but so far I'm thinking that its very do-able.

Yes, yes I know some of you will say just keep the new truck complete, but I much prefer the look and feel of the old GMT400s, and I want the performance and tech of the new trucks with the LML Duramax and all that. Also I know that it will take a lot of work to get the GMT400 chassis capable of not twisting and or breaking under that nearly 1000lb-ft of torque if it ever gets grip at low speeds or on launch by some miracle. Personal preference, don't need people telling me it's dumb or all that I just want some insightful help.



Also on a slightly related note, does anybody know of putting a built manual behind the LML? What are the computer issues and how are they solved? I absolutely despise automatics so I will be putting one behind my Duramax one way or another. Again personal preference people.

 

[Jrgunn5150]

GMT900's are CANBUS/GMLAN aren't they? If so, it would be easiest to get a standalone harness for the Duramax.

Duaramax engines DO fit in the 400 chassis, so I see no reason why the body couldn't sit on a 900 chassis if you moved the mounts around.

And again, Duramax's do fit in the 400 chassis, that's probably the easier route to take.

 

[LML Duramax 95 Z71]

GMT900's are CANBUS/GMLAN aren't they? If so, it would be easiest to get a standalone harness for the Duramax.

Duaramax engines DO fit in the 400 chassis, so I see no reason why the body couldn't sit on a 900 chassis if you moved the mounts around.

And again, Duramax's do fit in the 400 chassis, that's probably the easier route to take.

Yeah that's what I was thinking. I understand the engine swap may be easier but with all that torque, the whole chassis would be subjected to much more strain than it was ever designed to handle.

What is CANBUS/GMLAN exactly?

 

[Jrgunn5150]

My point with Duramax's fitting in a 400 chassis, is that there are already some running around supporting the motor just fine. The only broken frames I have ever seen were from rust.

CANBUS/GMLAN is how vehicles are wired nowadays. The wires aren't just carrying electricity, they are carrying data. The taillights, washer reservoir, seatbelt, seat, every single thing has a sensor and communicates to the ECU, and the ECU is looking for those signals.

 

[LML Duramax 95 Z71]

My point with Duramax's fitting in a 400 chassis, is that there are already some running around supporting the motor just fine. The only broken frames I have ever seen were from rust.

CANBUS/GMLAN is how vehicles are wired nowadays. The wires aren't just carrying electricity, they are carrying data. The taillights, washer reservoir, seatbelt, seat, every single thing has a sensor and communicates to the ECU, and the ECU is looking for those signals.

So, any missing piece of the puzzle means difficulties?

 

[Jrgunn5150]

So, any missing piece of the puzzle means difficulties?

If starting with a CANBUS vehicle yes. IDK if the LML is on that system or merely OBDII. On a recent episode of Roadkill on YouTube, they Late Model Hemi swapped a 69 Charger and had to use the dash, taillights, shifter, everything to get it to run. Looked like poop.

 

[LML Duramax 95 Z71]

If starting with a CANBUS vehicle yes. IDK if the LML is on that system or merely OBDII. On a recent episode of Roadkill on YouTube, they Late Model Hemi swapped a 69 Charger and had to use the dash, taillights, shifter, everything to get it to run. Looked like poop.

Yeah roadkill, I love it! I think LML is just OBDII though so it shouldn't be that big of a deal.

 

[thz71]

If starting with a CANBUS vehicle yes. IDK if the LML is on that system or merely OBDII. On a recent episode of Roadkill on YouTube, they Late Model Hemi swapped a 69 Charger and had to use the dash, taillights, shifter, everything to get it to run. Looked like poop.

Not true. That can all be tuned out they used all of that stuff because they wanted to not because they had to. Have you done any measuring g to compare the frame widths from a 400 to a 900?

 

[House003]

I would love to see this done.

 

[LML Duramax 95 Z71]

Not true. That can all be tuned out they used all of that stuff because they wanted to not because they had to. Have you done any measuring g to compare the frame widths from a 400 to a 900?

The body of the 900 is a little bit wider but not a huge amount so I would assume the frames are the same way. Even if it is, I can just make some steel body mount brackets to extend the cab mount to the frame mount.