Duramax Conversion

[jim1131]

Hello Steel Soldiers,

I have a donor truck with a Duramax LLM for a swap on my 1165. Im thinking of putting the full drive train complete with trans, transfer case, wiring harnesses and control modules and want to know if anyone in this group has done a complete swap off another truck. What problems might I run into? I know that the exhaust pipes need to be worked on as well as drive shaft issues too but will the transfer case mated to the Allison trans clear the frame on my 1165? Will my factory front and rear air conditioning run on a 12 V system? I will be using the original alternator and air conditioning compressor currently mounted on the Duramax. The engine is running great and has low miles for that year truck.

 

[Mogman]

How not to install a Duramax in a M998

Well hopefully this will not be the epitaph for this project, I thought a thread with the progress and possible pitfalls that lay ahead might be interesting to someone, constructive criticism, hints and comments from actual experience will be of course welcome. Some of this has been told before...

www.steelsoldiers.com

I did a M998 but many of the issues will be the same, I was not able to fit the late style fuel tank in this conversion.
I just turned 14K and had to "redo" very little.
I am by NO means saying this was the correct way, just how I did it.

 

[jim1131]

This is a REV truck with the ECV front, I believe it does have the new style fuel tank and plenty of room for the radiator fan in the front.

 

[Mogman]

I put two alternators on it and ran dual voltage system, no the AC will not run on 12V, no problem with room for fan
You will need to reduce the height unless you want to do a large lift, I did mine with 2" would recommend 3"

 

[Mogman]

Putting dual alts on the LMM is easy, it already has the mounts or at least most of it

 

[Mogman]

BTW you need to ditch those 3.07 gears, seems the T/C front output shaft does not like running with the engine turning 2700+ rpm at 75mph, (multiple failures) I am running the 2.56 gears and turning about 2150RPM at 75MPH which is about 100RPM or so higher than my 2008 GMC C3500HD LTZ with 3.73 gears turns at 75MPH, no need to twist that DMAX that high, I am going when I can afford it to 39.5" tires which should put me close to stock RPM.

 

[Vapor Trail]

I wonder if there's a better setup or better bearing to use for that?

 

[Mogman]

I wonder if there's a better setup or better bearing to use for that?

There is no logical reason to twist the Duramax at 2700RPM+ at normal highway speeds, even without the T/C failure issue.
BTW when it does fail it takes out the engine (usually rips the pan off) and transmission, just rips the side out.
There seems to not be an issue with the 2.73 gears although I do not understand why anyone would not want the lowest ratio available.

 

[Vapor Trail]

Oh sorry, I get it. I thought you were talking about that prop shaft bearing mounted between the t/c and the diff. Your talking about the actual t/c shaft