Duramax LMM with Allison

Q & A Section:

Your Lead time says 2 weeks, are you running on time? - That is our current lead time and we take great pride in meeting our agreed completion dates.  If we are running longer the website will be adjusted to reflect accordingly.  Please watch the video What Happens and What to Expect on the contact page for all of the details on timing.

What Transmission Can I use? - See the Statement of Work above.  Most of our customers use the Allison Transmission that was originally paired with the Duramax from the factory.  If using an Allison please note that the 5 speed must be used with LB7 and LLY and the 6 speed must be used with the LBZ and LMM.  The 4L80/85E that was in a Van type Chassis is another option and others choose the ZF6 Manual that was also available from the OEM.  Your choices are only limited to what will bolt up to the engine.  We can set up the harness to work with just about anything including Marine Transmissions, Pulling Truck Clutch Only and Air Boat Gear Reduction Boxes.  Please email for more details on modifying the harness when swapping the transmission that was bolted to your Duramax when it left the factory.

Do you sell harness parts or connectors? - We no longer sell individual parts, terminals or connectors to the public but will happily support our current and previous harness customers with the parts they need.

Will you modify, fix, refresh or clean up a harness for a factory 2001 or newer Duramax Pickup, Kodiak or Topkick? - We only support standalone conversions of Duramax harnesses and nothing else.  A standalone harness is intended for engine swaps in vehicles that did not originally have a Duramax Engine from the factory.  Generally, the swapped vehicles are pre 1996.  We can not work on any harness going back into any GM truck newer than 1996 due to Federal Emissions Regulations.

Will you build a Plug and Play harness for OBS, GMT400, GMT800, GMT900, Top Kick, Kodiak, H1 Hummer, H2 Hummer, Tahoe, Suburban, (basically any Chevy - GMC Truck) or any other make or model vehicle to swap in a Duramax? -  Due to the complexity of modern vehicles and their control systems we specifically avoid any "Plug and Play"type swaps.  Nothing about a standalone harness will plug into the vehicle you are working on.  All tie in is completely up to the installer/customer and is not something we support in any way.

Can you build a harness to swap a newer Duramax where an older Duramax was?  (such as 01-05 truck getting an LBZ or LMM) - See the answer directly above.  Note: older engines in newer trucks (such as an LB7 in a truck newer than 2004) is the same answer as above.  Federal Emission laws prevent us from providing this service.

Will you add length to the harness? - We do not offer changes in length.  Every harness leaves our door at the exact same length it was when it left the factory.

Will Tow-Haul work? - It unfortunately does not work in standalone setups.  In the donor truck, Tow Haul was controlled by the BCM in all 2001- current trucks.  Since the BCM is not used in a standalone setup Tow Haul is not possible.

Will Tap Shift work? - We do not supply pigtails for Tap Shift Input.  Contact Fleece for LB7 and LLY or Dmaxswap for LBZ Tap Shift Solutions.  LMM is not available as the function was handled in the BCM.

Will the Electronic Transfer Case Shift work? - That is a completely separate system in the donor vehicle and is not part of a standalone harness.  Contact Dmaxswap.com as they have a solution for LB7, LLY and LBZ Electronic Transfer Cases.  Otherwise swapping to a manually shifted t-case is popular.

Can you add Idle Up or AC request Idle Up? - An AC compressor will not stall a Duramax so this feature is not needed in standalone.  As for an Idle Up button, we do not support that feature in any of our Duramax Standalone harnesses.

I'm doing a 4 Wheel Drive Frame Swap.  How do I get my axle to engage? - Although that circuit is not part of a standalone harness we will provide our harness customers with the schematic and pin-out of the front axle actuator if needed.

How do I handle Starter Solenoid Control, Park-Neutral Starter Interrupt (Neutral Safety) and Back up Lights? - If you are swapping into a vehicle that has the 1969-1994 GM type steering column (with the Automatic shifter on the column) all of those circuits are already in your truck.  We do not provide the purple wire that goes to the starter as that is part of your vehicle side electrics and those circuits are completely up to the customer and/or the installer.  LB7 and LLY will have Starter Interrupt and Back Up Lamp Pigtails labeled.  99% of our customers do not need them as those functions are in the swapped vehicle shifter.  If you are the 1% we will send the schematics of the switch on the side of the trans so it can be utilized.  You will need to use a relay as the switch is not rated for the current requirements of a Starter Solenoid.  Determining how to use the Allison PNP (NSBU) Switch for Starter Interrupt is completely up to the installer.  We only supply the schematics as a reference.

How will I handle AC Compressor Clutch Control? - We will return the Compressor Clutch Pigtail in the box.  You or your installer can then tie the compressor to your vehicle's AC management system.  Whether it's an original factory air or a Vintage Air type setup it will work perfectly with the correct fittings and refrigerant charge.

Can the ECM Control Electric Fans? - Unlike LS ECM's the Duramax ECMs do not control Fan Relays. A Derale Thermoswitch is the easiest solution.

Will Cruise control work? - Yes LB7, LLY and LBZ have a cruise function directly in the ECM and every harness is set up with those pigtails standard.  It will work with any GM cruise switch on the turn signal stalk of a 1969-1994 GM Type Column.  Other alternative switches are available through Rostra and Dakota Digital.

Can I reuse the Donor (2001 - Up) Gauge Cluster? - Some if not all of the gauges in the donor cluster were controlled by the BCM which is not part of standalone harnesses as a result they cannot be reused.

What Gauges can I use? - LB7, LLY and LBZ ECM's have outputs for Speed and Tach signals.  With an aftermarket Programmable Speedometer or Tachometer you can hook up to those signals and program the gauges to work with the Duramax ECM easily.  Contact your gauge manufacturer for more info. For Water Temp and Oil Pressure your gauge cluster will have come with senders which will need to be installed in the Duramax block.  Factory Gauge clusters such as the ones in Squarebody Chevys can be used but the installation and connection is completely up to the installer.  Tons of info on various forums will cover that subject. Note:  Only 01-02 LB7 will have a pigtail for Oil Pressure to directly feed a gauge.  The easiest solution is using the OBD port for Gauges that comes on every harness we produce to plug your cluster in and have it pull all of the data directly from the ECM.  By far this is the easiest solution for LB7, LLY, and is the only solution for the LMM Family.  Note that Dakota Digital changed their BIM module in 2021 and the part number ending in -2 will no longer work with the LBZ ECM.  Dmax swap is working directly with DD engineering to correct the problem but it will require DD to release a revised part number.  The timing of the new part is unknown at this time.

Can you lengthen or add a second OBD Port? - A splitter is a much more simple and cost effective solution.  Note: we do not recommend more than one device on the port.  Multiple devices can cause communication problems between the ECM and TCM.  If you need a longer port, extensions are readily available on sites like Amazon and Ebay.

Do you support LML LGH or L5P? - We are partnered with www.dmaxswap.com in the support of LML and LGH.  The L5P prototype harness has been built and programming/testing is in process at Dmaxswap.  Contact Dmaxswap.com to be put on the list for the product launch.

Do you support Cummins, Powerstroke, or any other harnesses? - At this time we only support Duramax and our R&D for 2022 is closed for taking on projects outside of the Duramax Family.

Do you build Allison standalone harnesses for Cummins Swaps? - We only support Allison Transmissions when they are part of a Duramax Swap.

Plain English Disclaimer:  We will provide additional data as needed but skills on the customer end are required and any attempts to make any of the above-mentioned systems, conveniences or features function are completely up to the customer and/or the installer.


For $576.00 your LB7 LLY LBZ or LMM Duramax ECM/TCM (Engine to Chassis) harness is reworked to standalone and will look factory fresh.  Right now turn around is 2 weeks.  It will have a Delphi Automotive Under Hood Rated Fuse/Relay block with a legend and dust cover and a 5 foot long OBD Port.  Just three connections are required to make the engine and transmission function as a Standalone: 12V Battery, 12V Ignition (Key On) and a Single Ground. Your harness will be ready with the correct connector to accept the donor truck Accelerator pedal.  Your Donor Harness is Cleaned and Degreased and only High Temp Tubing/Tape is used.  Your Donor will be completely refreshed and you will be shocked at how good it looks compared to what you sent.  One customer said, "It was like Christmas Morning opening the box."  Our goal is to have every customer that happy with our work.

Express and Savanna Van harnesses add $175.00 we'll greatly simplify the layout making the trans section one piece.  Topkick/Kodiak add $175.00 to reconfigure for a layout that will allow ECM/TCM/Fuseblock mounting 10 feet from the engine.  (Topkick/Kodiak Only)

Much more than adding a fuse block is done.  Here's what we do to every harness that comes through our door:

When your donor harness arrives it will be Tagged, Peeled, Degreased and fully Inspected under magnification.  When that process is complete you will be contacted by phone (3-4 business days after arrival) to build up the work order for your specific setup.  From that point the harness will be finished and ready to ship within the 2 week time frame.  It will arrive looking like a new harness since we only use High Temp Split Loom Tubing, GM Spec High Temp Tape, and printed plastic Labels.  No butt connectors, gooey household electrical tape, swap meet loom or masking tape anywhere!  All excess terminals and wires are removed completely from the ECM and TCM not just chopped off at the connectors. Minor repairs to crash or rodent damaged wires (up to 10) are included in the standard price.  If you have damaged or missing connectors replacements will be quoted on our work order call.  We stock Every connector for Duramax and Allison so your lead time won't be longer if a replacement connector is needed.

Here's an example of our standard work order:

Convert customer supplied Duramax engine and transmission harness for standalone use as follows:

• Remove all factory convoluted (loom) tubing and tape.  Completely clean and degrease harness.

• Retain Allison TCM or setup for 4L80E, 4L85E, TH400, Powerglide, or Manual Transmission. (customer choice)

• Reconfigure harness for individual connector runs and a centralized ground.

• Install a Delphi Covered Fuse Block with ECM, FICM and TCM power relays as needed. 

• Check all terminals and bulk wire runs under magnification and electrically test power and ground circuits.

• Install OBD2/ALDL Connector - 4 Feet Long. (will reach under the dash in most applications)

• Identify Park Neutral Position connection pigtails and provide schematic for starter on request. (LB7 and LLY only)

• Identify Back Up Lamp connection on PNP switch and provide schematic on request. (LB7 and LLY only)

• Retain Duramax Alternator controlled by PCM.

• Retain or Remove Glow Plugs and other circuits per customer direction. (Off Road, Competition Use Only)

• Identify Cruise Control pigtail connections at PCM and provide schematic on request. (LB7, LLY and LBZ only)

• Remove all Air Conditioning control related circuits. Return Compressor Pigtail to customer for use with Vintage Air or other AC.

• Remove Coolant Level indicator control circuit.

• Identify Wait to Start, TCC and MIL lamp pigtail connections at ECM.

• Identify Tach, Speedometer, and 4WD Low pigtail connections at the ECM. (LB7, LLY & LBZ only.)

* Every Duramax Harness is re-covered with new GM Spec High Temp Loom and High Temp Harness Tape.

* Express Van and Savana harnesses can also be converted. (they will be significantly simplified especially the trans section)

​* Pricing is $576.00 for a Truck Engine to Chassis Harness and $671.00 for a Van Engine to Chassis Harness. 

ECM and TCM Tuning is also available.  For example a base standalone tune (aka Single Tune) is $350.00 or an EFI Live DSP5 standalone + performance tune with Switch is $550.00.  Contact DMaxSwap.com for additional details.  

Please do not ship any modules to us.  You need to retain your modules and work with the tuner directly.  ​​