Duramax 6.6 and Allison Transmission Swap

[Agelai]

I’ve read many threads on this, but no one really put together the cost to do this. Here’s what I’ve found so far, tell me what I’m missing and I’ll add it.

price for duramax swap


Complete engine drop in: $13,500
Allison transmission: $4,000
Radiator and hoses:
Mounts:
Body lift:
Axles:
Gauges and sending units:

 

[TOBASH]

Engine computer, transmission computer, custom coding for engine computer, acceleration and brake pedals wired into the system, custom wiring harness, custom motor and tranny mounts, body lift kit, custom exhaust with air sensors, intake with air sensors. Custom oil and transmission dipstick tubes, custom fuse box with custom relays, possibly custom steering column to get around the custom exhaust system. Probable conversion to 12v with replacement of windshield wiper motor/lights/etc…

That’s just off the top of my head.

Read Mogman’s thread about what he went through.

 

[Mogman]

I bought a wrecked truck, that gave me all the major components needed IE accelerator pedal, ECM/TCM/TTCM. wire harness etc.
I was asked one time how much it cost but it was actually only around 8-10K total, the wrecked truck cost under 4K delivered.
And it took 7 months of work, but I am old and slow and fairly anal about getting it right.
by the time I got finished I swore I would NEVER do that again but after the first time I drove it I started looking for another donor M998

 

[Agelai]

Ok I’m scared now…. I was thinking it would be a little simpler.

 

[springer1981]

Ok I’m scared now…. I was thinking it would be a little simpler.

If you've never done something like this before, this isn't an easy one to start with. There is nothing that "bolts in" and nothing is "plug and play".

When I initially bought my HMMWV I bought a 2002 Chevy 3500 with a 88,000 mile Duramax the same day with the intentions of doing a swap. After driving my HMMWV for a while I decided it ran too good to chop up for the Duramax. This isn't a daily driver and I didn't need it to do highway travel etc. I ultimately rebuilt the Chevy completely with a custom build. Then I did a 4L80 transmission upgrade in the HMMWV and I have been very happy with it.

I would have been comfortable doing the Duramax conversion but it is a LOT of work to do it right. You are basically building a HMMWV from the ground up.

 

[Mogman]

Ok I’m scared now…. I was thinking it would be a little simpler.

IMHO if you do not have a well equipped shop including a lift than it would be a hard project to do well, that is why "shops" that do this charge 12-20K just in labor.
If you have not already done so go and look at my build thread,

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

BY NO MEANS am I saying this is the only way to do this or if it is even the right way to do it but I do have 5K on it so far and have not have to go back and "redo" anything, except for replacing the GPS speedometer.
Is it worth the effort, you are DAMN RIGHT! but still a major effort.
Now having said that there was at least one company selling the "complete" install kit for 12K, without the actual donor parts, engine trans etc. etc.

 

[thoner7]

What are the companies doing these swaps? I can admit it would be way over my head. I’d feel more comfortable trying a 12v Cummins but even that I am not qualified to do.

 

[thoner7]

I bought a wrecked truck, that gave me all the major components needed IE accelerator pedal, ECM/TCM/TTCM. wire harness etc.
I was asked one time how much it cost but it was actually only around 8-10K total, the wrecked truck cost under 4K delivered.
And it took 7 months of work, but I am old and slow and fairly anal about getting it right.
by the time I got finished I swore I would NEVER do that again but after the first time I drove it I started looking for another donor M998

4k for a donor truck seems really cheap

 

[Mogman]

What are the companies doing these swaps? I can admit it would be way over my head. I’d feel more comfortable trying a 12v Cummins but even that I am not qualified to do.

Probably not any easier, would need to adapt an Allison.
I have no idea who is doing these, last I heard it is a 25K swap with a used engine, probably higher now.

 

[springer1981]

Probably not any easier, would need to adapt an Allison.
I have no idea who is doing these, last I heard it is a 25K swap with a used engine, probably higher now.

Why would he have to adapt to an Allison? The Allison is harder to deal with from a standalone TCU stand point. If he considers a Cummins swap he could much more easily adapt it to a 4L80 that already bolts up to the rest of the drive train. Basically just an engine swap.

 

[Mogman]

Why would he have to adapt to an Allison? The Allison is harder to deal with from a standalone TCU stand point. If he considers a Cummins swap he could much more easily adapt it to a 4L80 that already bolts up to the rest of the drive train. Basically just an engine swap.

Sorry, I did not consider that, the 4L80 is just a FORB 3L80 which is the least efficient transmission GM ever produced and the 4L is not far behind, maybe not too big of a deal if one has enough horsepower to spare. (read not a big fan)
The 4L is not one I would go to if I had a choice and the OD is rather puny at 0.75:1 than the Allison at 0.61:1 or the 6L90 (easy enough to stand alone, I have one in the Detroit) at 0.67:1 and it is a much more efficient transmission than the 4L, one of the reasons why the Detroit (a helmit top at 7300lb, like pushing a brick through sand) cruises comfortably at 75MPH@2300RPM, now that transmission would be a decent match with the turbo 6.5L and the 3:07 gears.
EDIT Oh yes the 6L has a rock crawling 4.03:1 1st gear, the 4L has a 2.48:1

 

[VP0985]

I bought a wrecked truck, that gave me all the major components needed IE accelerator pedal, ECM/TCM/TTCM. wire harness etc.
I was asked one time how much it cost but it was actually only around 8-10K total, the wrecked truck cost under 4K delivered.
And it took 7 months of work, but I am old and slow and fairly anal about getting it right.
by the time I got finished I swore I would NEVER do that again but after the first time I drove it I started looking for another donor M998

This is the best way in my experience. Buying a wrecked donor truck. Copart is an easy website to navigate and the auctions are Interesting to watch live.

Sent from my SM-G990U using Tapatalk

 

[thoner7]

I’m a total novice but my understanding was that a company like ca conversions has figured out the Allison stand alone issue and imyou could order a reman unit straight from them.

 

[thoner7]

I assume the duramax would be quieter than the Cummins right?

 

[Retiredwarhorses]

Dmax conversions are $50-75k….anyone who says thats crazy has just never done one, the only way to keep
costs down is to do it your self And source your own parts.
Don’t believe me…make the calls to Mtn Machine, Predator etc…and when they quote you? Add another $15-20k on it, especially if it’s Predator, the main thing you need to really pay attention too is WHO is doing the work, don’t follow the money, follow the shop.
I’ve been asked numerous times to start doing them in the shop, just not interested in the headaches of doing them, I already have to work on them when they come in, it’s like owing a super expensive Italian GF.

 

[Mogman]

Dmax conversions are $50-75k….anyone who says thats crazy has just never done one, the only way to keep
costs down is to do it your self And source your own parts.
Don’t believe me…make the calls to Mtn Machine, Predator etc…and when they quote you? Add another $15-20k on it, especially if it’s Predator, the main thing you need to really pay attention too is WHO is doing the work, don’t follow the money, follow the shop.
I’ve been asked numerous times to start doing them in the shop, just not interested in the headaches of doing them, I already have to work on them when they come in, it’s like owing a super expensive Italian GF.

My experience is different than RWH, with the exception of being able to blow out the boots on the cheap Chinese half shafts I have not been able to break anything, and believe me I have tried and I have the base M998, going on 10K and as dependable as any other vehicle I own again with the exception of the boots on the half shafts.
My cost including the donor vehicle was around 10-11K and it is SOOO much more relaxing to drive as it does not seem like it is about to explode any second.

And yes it is much quieter than the Detroit as far as noise from under the hood.

Disclaimer: I have been stuffing diesels where they do not belong since the mid 70s when my brother-in law (RIP Leon Linton!!) and I were stuffing Perkins 6-354s in 3/4 ton Chevy trucks and I have a fully equipped shop. and I fabbed up just about everything myself.

But as RWH has pointed out is is not for the faint of heart and was probably the most challenging swap I have done.

 

[Retiredwarhorses]

My experience is different than RWH, with the exception of being able to blow out the boots on the cheap Chinese half shafts I have not been able to break anything, and believe me I have tried and I have the base M998, going on 10K and as dependable as any other vehicle I own again with the exception of the boots on the half shafts.
My cost including the donor vehicle was around 10-11K and it is SOOO much more relaxing to drive as it does not seem like it is about to explode any second.

And yes it is much quieter than the Detroit as far as noise from under the hood.

Disclaimer: I have been stuffing diesels where they do not belong since the mid 70s when my brother-in law (RIP Leon Linton!!) and I were stuffing Perkins 6-354s in 3/4 ton Chevy trucks and I have a fully equipped shop. and I fabbed up just about everything myself.

But as RWH has pointed out is is not for the faint of heart and was probably the most challenging swap I have done.

its not a matter of if something will break, just when…the most common is differential stuff, especially stub Axles, a lot of this also has to do with the tune, make it dump 700ft lbs and 1k of HP and you got issues.
99.9% of all folks pay a shop for this conversion, that’s why I stated as such…you can’t use your conversion as a bench mark for the 99.9%, someone who has little to no mechanical abilities should start calling the shops that do this to get a better idea on price…but be prepared for sticker shock.

 

[thoner7]

FWIW Plan b has 46k on their website for a swap. Mash motors is 41k Predator is 59k.

Mogman- how much do you charge lol!!

 

[Mogman]

FWIW Plan b has 46k on their website for a swap. Mash motors is 41k Predator is 59k.

Mogman- how much do you charge lol!!

Well the cost is only half the story, it took me 7 months to finish of course I had a regular job at the time and it was my first Dmax conversion and I am old and lazy!

I also rewired the entire truck from the taillights to the headlights including a full set of stepper motor (electronic/analog) gauges, real trucks have needles!

The entire build I kept telling myself I would NEVER do THAT again, but after I finish the FAV and the Unimog I will probably rip the GEP turbo 6.5 and the 6L80 out of the Detroit and stuff a Dmax in it, if I live that long.....

 

[Mogman]

I never tried 1000HP, my engine has a big Cheetah turbo and a Fleece pump and injectors it can probably be coaxed to well over 700HP.
If you can afford a 1000HP Dmax you can afford to keep your mechanic busy.
At this time I am running the stock 365HP/660FT/LB tune and that is plenty even with the S788 shelter on back.
I was running a 435+HP tune in the beginning when I was trying to break stuff but I did not like the high EGTs, now I know 12-1300F continuous while towing etc. is fairly normal for the Dmax, would fry a Detroit.
I am running 900-1100F with this tune.