Duramax Van Harnesses
The Duramax 6.6 turbo diesel was offered in Chevy and GMC van applications in the following configurations:
LBZ/4L85e
LMM/4L85e
LMM/6L90e
LML(LGH)/6l90e
The Duramax used in Van application is significantly de-tuned far below the pick up truck power levels due to the transmission being significantly limited on torque capability. These engines are all tuned to a maximum of 300hp and the operating systems used for the engine/transmission control are specifically designed for shuttle bus style, torque delivery and shift quality. The important limitation is the maximum torque capability of the transmission and the Duramax engine easily produces 800 foot pounds of torque with only slightly improved permanence tuning which is far beyond the torque handling capability of the 4L85 and 6L90 transmissions. This is why the torque management is so extreme on up shifts to protect the transmission, but it is also why the shift quality is very poor and there is harsh Defuel on up shifts.
The LMM Duramax, produces:
660 lb-ft of torque with an Allison 1000 and OEM pickup truck calibration
Only 460 ft-lbs max torque capacity with a 4L85e
Only 531 ft-lbs max torque capacity 6L90e
Harnesses we do not support:
In all of these applications our strongest recommendation is to ditch the 4L85 or 6L90 transmission and convert to an Allison six speed. We can utilize your van harness and convert it to accept a six speed Allison transmission control system. You will have to purchase a different transmission control module to work with the 6 speed Allison.
We can support the 4L85 transmission as an “Engine Only” standalone harness to run behind any Duramax engine and utilize a US shift standalone transmission control system for the 4L85e so you can get maximum performance and ideal shift quality, especially when modifying the 4L85 transmission to handle more than 500ft-lbs of torque with mods like 300m input shaft and other internal upgrades..
For the LMM/6L90e the only option is to switch to either the Allison 6 speed or 4L85e. We do not support the 6L90e behind any LMM Duramax.
For the LGH/6L90e we also recommend converting to the six speed Allison but we can support the 6L90 although it will only be programmed with stock power level.