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I have a 2006 LLY in a van chassis that will be going in a 61 GMC5500. It has the 4l80 transmission an being from a van is only 460lb/ft of tq. My research has shown me that this engine is physically the same as an LBZ. Can I run an ECM from a pickup truck and achieve the same hp/tq levels as a pickup? My plan is to also upgrade to an Allison.
 

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Uh, in a word . . . NO!

But, in a few words: LBZ compression is lower and the torque curve is different. Why is that important? Because the 6-speed TCM is looking at the TPS, temps, rpm, converter lockup, and load, before making a shift decision. In addition, all of the engineering software was based on the rear axle ratio and truck GVW. Then the ECM and fuel map are doing about the same thing. So to transplant all of the computer stuff to your grossly different 5-speed LLY and hope it will work . . . it won’t.

There has been 2 decades of misinformation and confusion on the LLY and LBZ differences. The best synopsis I have seen was 10-12 years ago in a post I have long forgotten. It is listed verbatim below and my thanks to the original author. Find a COMPLETE LBZ, 6-speed package, do the transplant, throw your stuff away.

Changes include:
Cylinder block casting and machining changes strengthen the bottom of the cylinder bores to support increased power and torque
Upgraded main bearing material increases durability
Revised piston design helps lower compression ratio to 16.8:1 from 17.5:1
Piston pin bore diameter increased for increased strength
Connecting rod “ I ” section is thicker for increased strength
Cylinder heads revised to accommodate lower compression and reduced cylinder firing pressure
Maximum injection pressure increased from 23,000 psi (1,585.8 bar) to more than 26,000 psi (1,792.6 bar)
Fuel delivered via higher-pressure pump, fuel rails, distribution lines and all-new, seven-hole fuel injectors
Fuel injectors spray directly onto glow plugs, providing faster, better-quality starts and more complete cold-start combustion for reduced emissions
Improved glow plugs heat up faster through an independent controller
Revised variable-geometry turbocharger is aerodynamically more efficient to help deliver smooth and immediate response and lower emissions
Air induction system re-tuned to enhance quietness
EGR has larger cooler to bring more exhaust into the system
First application of new, 32-bit E35 controller, which adjusts and compensates for the fuel flow to bolster efficiency and reduce emissions"
 

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Uh, in a word . . . NO!

But, in a few words: LBZ compression is lower and the torque curve is different. Why is that important? Because the 6-speed TCM is looking at the TPS, temps, rpm, converter lockup, and load, before making a shift decision. In addition, all of the engineering software was based on the rear axle ratio and truck GVW. Then the ECM and fuel map are doing about the same thing. So to transplant all of the computer stuff to your grossly different 5-speed LLY and hope it will work . . . it won’t.

There has been 2 decades of misinformation and confusion on the LLY and LBZ differences. The best synopsis I have seen was 10-12 years ago in a post I have long forgotten. It is listed verbatim below and my thanks to the original author. Find a COMPLETE LBZ, 6-speed package, do the transplant, throw your stuff away.

Changes include:
Cylinder block casting and machining changes strengthen the bottom of the cylinder bores to support increased power and torque
Upgraded main bearing material increases durability
Revised piston design helps lower compression ratio to 16.8:1 from 17.5:1
Piston pin bore diameter increased for increased strength
Connecting rod “ I ” section is thicker for increased strength
Cylinder heads revised to accommodate lower compression and reduced cylinder firing pressure
Maximum injection pressure increased from 23,000 psi (1,585.8 bar) to more than 26,000 psi (1,792.6 bar)
Fuel delivered via higher-pressure pump, fuel rails, distribution lines and all-new, seven-hole fuel injectors
Fuel injectors spray directly onto glow plugs, providing faster, better-quality starts and more complete cold-start combustion for reduced emissions
Improved glow plugs heat up faster through an independent controller
Revised variable-geometry turbocharger is aerodynamically more efficient to help deliver smooth and immediate response and lower emissions
Air induction system re-tuned to enhance quietness
EGR has larger cooler to bring more exhaust into the system
First application of new, 32-bit E35 controller, which adjusts and compensates for the fuel flow to bolster efficiency and reduce emissions"
The vans never got a LLY.
 
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