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:

– OEM LBZ/4l85e with T42 TCM van harnesses – OEM LMM/4l85e with T42 TCM van harnesses – OEM LMM/6l90e van harnesses.   * All of these can be converted to “Engine Only” for use with 4l85e and US Shift standalone trans control or switched to Allison 6 speed.

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.

Dmax Swap
Phone Number

We know you prefer to talk on the phone rather than typing…BUT

At Dmax Swap we get a lot of technical questions, and that’s great because we have the answers when it comes to Duramax conversions; We have put a Duramax in everything but an airplane!!! We have been tuning with EFILive and building high performance Duramax powered vehicles since 2002, so there is nothing we can’t help you with. We have you covered from complete engine and transmission builds to custom calibrations for any application.

We always contact customers, that have purchased tuning from us, prior to programming their modules.  We have each customer follow our ordering guide which walks them through the ordering process, consisting of purchasing products, completing a tune request form so that we can document their build and give us the proper information to make recommendations as well as design the calibrations to work for their build and finally, where to send their donors.  We are happy to provide recommendations for components or other performance upgrades and even recommendations for cooling, electrical, and even transmission and transfer case solutions.  But we need DATA!

We make email our primary form of communication. This benefits both the customer and us mutually:
– Questions are answered and documented.
– We have all of the information needed to properly formulate a recommendation or solution.
– Both the customer and we have records of what was discussed and delivered.
– The communication can be organized with the proper customer information or order number

We don’t provide support for:
– Other companies tuning, electrical, or harness products.
– Late model integrations. This means we only support vehicles prior to 1998.   This doesn’t mean we don’t know how to put an LBZ in 1/2 ton 2003 Chevy Tahoe and make it all work… it’s just not the focus of our business or part of our business model.

We have seen the value of keeping things documented for reference and clarity; It saves significant time and reduces errors. We work off of this model and have written this article to explain it briefly so our visitors/customers can understand the logic. As new common questions arise, we continue to update the FAQ, refine our ordering guide and even create videos, to make the experience as complete and streamlined as we can.

We look forward to hearing from you and helping you save the world… One Duramax at a Time!!!