Lil Red - Duramax 6600/Allison 1000 Conversion & OBS/NBS Dash Conversion

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I've been asked a few times these past few months about the new body style (NBS - 1999-2007 model year) dash I installed in Lil Red (1989 Chevy K1500).



They asked whether the newer dash was too wide for the OBS (Old Body Style) cab interior, they asked about the HVAC (heating-venting-air conditioning) package used in my truck, and they asked about the electrical harnesses I used.



The newer dash is wider than the original, but it fits if the door panels are modified to be as thin as possible. The top photo shows the modified 1989 door panel. Basically, the door panel is only about 1/8" thick where it fits against the new dash. I cut that section out of the original door panel and plastic welded in a piece of 1/8" ABS flat sheet to replace it. Then, the new ABS piece, once shaped to fit exactly, was covered in vinyl imitation leather. The final touch was using an automotive interior spray color dye to get the door panels to color-match the new dash. Once completed, the ends of the dash and the door panels "just" touch when the doors are closed. The above photo shows just how much of the original door panel had been removed.

The Heating/Venting/Air Conditioning (HVAC) package beneath the dash and the dash-mounted controller I'm using are the original 1989 units. However, if doing all this again, I'd be tempted to install a new HVAC package that matched the model year of the new dash. This way, the ducting could be easier to complete and the dash HVAC controller would be plug-n-play with both the HVAC package and the new wiring harness borrowed from the Duramax/Allison donor truck.

Speaking of electrical harnesses... I recommend using the GM factory Duramax donor truck's electrical system harnesses along with a reprogrammed factory ECM (Kennedydiesel.com and others can reprogram your factory ECM to correct for tire size and final gearing, as well as remove the factory security key lock code, if you wish - though I recommend keeping it if you can). With the exception of Lil Red's lighting system (head/tail/courtesy, etc) the remainder of the truck's wiring was swapped out for the new. This actually made the conversion easier and simpler - though you have to be committed once the original wiring system has been stripped out...

Beginning with the complete OE Duramax donor's wiring harnesses and various control modules allow you to incorporate any of the luxury and safety features into your build that are found in the newer trucks. These optional features don't have to be used/incorporated, but they are possible when using factory parts. You can pick and choose. For example, the airbag system could be transferred to your earlier truck. The 4-wheel ABS system could be transferred. Then there's the security system, audio system, climate control, even OnStar and any other feature that was found in your Duramax donor truck. In talking to (or through email) hundreds of conversion project owners, these factory offered features have been incorporated in part or in whole in some number of the trucks that have been converted through the years. The various aftermarket harnesses/ECMs are more expensive and they don't provide for any extras. Plus... if your conversion maintains stock functionality, any GM dealer or diesel service tech can help you with trouble codes or routine troubleshooting - now and into the future. This makes your truck more valuable if you ever decide to sell it.



There's no going back... This is a very early photo showing how Lil Red's interior looked after the original dash and most of the wiring had been removed. The process was a little scary at this point, which helps to explain why it took time to make the decision...

The indecision about whether to strip out the original wiring (and swap the dash) cost me nearly a year, because at that point in time (late 2002) no one outside of GM had converted an earlier GM truck to D/A power. Seemed like a big-big risk at the time, given that this truck was such a peach to begin with, and here I was stripping out some very important parts that would make going back nearly impossible. Now, I know it's not a big risk...

Once I fully committed to moving forward, serious effort began in late 2003 and the truck first became drive-able in early April 2004 - some 4 months later. A short list of what was necessary to get to this point was motor mount design and fabrication, the dash conversion, intercooler fabrication/completion, a working air conditioning system, custom GM Corporate 9-1/2" 14-bolt 6-lug rear axle with a new Eaton posi-traction rear differential (plus new bearings, seals and ring/pinion gears), rear disc brake conversion using new 2003 model year factory GM parts, fully functioning push-button 4WD system (push-button control panel & transfer case control module), installing the new factory wiring harnesses for the NP263HD transfer case made for the Allison 1000 and Duramax engine control, new custom front/rear driveshafts, fuel tank/lines modifications, designing/implementing the layout for all of the under-hood components, completing the new bodywork/paint, installing an all new interior - including leather bucket seats/console and from new carpet/pad to a new headliner. There were a host of other additions that are likely not necessary for your project... Sounds like a lot, but it all came together in less than 4 months - when spending as few as 1 to a several hours/day working through the list as the design, photography and assembly of this brand new first-ever Duramax/Allison conversion came together.

All in all, I actually enjoyed the process, and my enthusiasm grew the closer to the finish line I became. In hindsight though, I know that having the Conversion Guide would have cut the time spent to complete the conversion in half - if I'd had it to begin with. Solutions for all of the challenging parts of the conversion that I wrestled with are all included in the Duramax Diesel Conversion Guide. And of course, all of the nuts and bolts of the conversion process are also included in the guide, showing how I did it. Plus, personal help is just a phone call or email away.

All that said, I ask that those planning a conversion to consider retaining their project truck's original dash and HVAC package, and just modify the truck's original instrument gauge panel surround to accept the newer instrument panel gauge cluster from the Duramax donor - and install the modified Duramax donor's steering column (you'll need to reposition the firewall mounting bracket on that column). This simplifies the total conversion. A typical car audio shop should be able to help you create a new gauge panel surround that adapts your current dash to accept the new Duramax gauge cluster - if you need help doing that part - this is what they do for custom speaker installations, etc.

I found that installing the new dash doubled the time it took to complete the conversion in my truck. You have to be committed and you need to accurately assess your skill level if you decide to swap the dash. If you really want the newer style dash, I suggest waiting till after the D/A conversion has been completed and you've been driving the truck for a while.



However, in all of the car shows and diesel events I've attended with this truck, I will say that I'm surprised that the newer style dash usually draws more attention/comments than does the clean OE appearance of the Duramax under the hood. Not sure what to make of that...

The dash install and most other items shown here are discussed in more detail in the Duramax Conversion Guide, and a bit more info can be found farther on in this thread.

>>> Nearly all of those who began with our Guide and mounts were able to complete their own conversion project without outside help. However, if anyone were to hit a snag in their project, I ask that they call or send me an email detailing the problem. There is a solution for every problem. Email/phone consultation is free. I've been through the process enough times to know how to help you. While it hasn't been necessary yet, I've offered a couple of conversion builders one last confidence boost before they began their own project... "bring your truck to me if necessary, and I'll help you get it running." - Jim