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Old 06-22-2009, 05:34 PM   #1
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Duramax / Allison?

I was at an extremely interesting place today; a company in southern California that is converting vehicles to hybrid, full electric, fuel cell & CNG. There were too many astonishing cars and trucks (including military...) to count. On our facility tour, we came across a small area filled with new engines & transmissions, from vehicles being converted. One that caught my eye, was a brand new GM Duramax turbodiesel & Allison transmission, out of an '09 Silverado. I casually asked if they wanted to get rid of the engine/trans, and they said thay would be happy to sell it, what would I like to offer. I threw out; $1000. They said they would think about it. One of the companies I'm partner in, is doing a complex fueling station for their testing, and our relationship is quite good. My thought is: would this powertrain be a reasonable conversion for a classic Airstream coach? I'm NOT a mechanic, although I have restored / rebuilt a few ancient British cars. I'll probably buy the engine/trans regardless, because it is brand new, I absolutely love the combination in my personal truck, and it's probably worth somewhere around ~$8-10k.


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Old 06-22-2009, 06:11 PM   #2
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There is doubt that this is a perfect combination. $1,000? I would be very surprised if they let the set-up go for so little but if so grab it! Funny that you should put up this post. My cousin and I were discussing just this past weekend what a perfect fit it would be for this combo fitted into a 345!

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Old 06-22-2009, 06:33 PM   #3
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I have often thought of the same combo. Jayco uses this combo in their Seneca motorhome line ($85k to $100k line). I personally think the Duramax/Allison combo would be far better then the 454 and TH400s that most have, though I am fairly certain that some significant fabrication would be involved.
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Old 06-22-2009, 11:25 PM   #4
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My Silverado 2500 has the Duramax / Allison. It has been an absolutely terrific combo. We tow a 16,000 lb fifth-wheel toyhauler, for a combined total around 23,000 lb. Tows beautifully, and anyone out west knows you have to climb pretty big hills just to get out of town... Those who have one know that you can't just call it a Duramax, the Allison trans is perfectly matched to the engine, and is a great unit. Ours (slightly modified 2005) puts out about 400 hp, & ~750 lb ft torque. It surprises quite a lot of folks...

There is a guy in FL who is a GMC motorhome "guru". He's been putting together a GMC coach with a Duramax/Allison conversion. Appears much more involved than using an Airstream coach, because the GMC is front wheel drive. The Allison trans is really bulky, and I think would work far better in a traditional RWD coach like the Airstream. I'll be talking with the place that has the engine, I think they would have all the electronics, etc, as they are converting the truck to hydrogen-electric hybrid. Too much of a project for me at this point, I would have a custom car builder do the swap.
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Old 06-23-2009, 04:42 AM   #5
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I wonder why the converter bought a diesel? It seems they would be several thousand dollars ahead per unit to obtain a gasoline version, unless they could make a profit on the sale of the discarded engine.
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Old 06-23-2009, 05:00 AM   #6
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AWESOME COMBO in my estimation! As "Inland Andy" once stated, "You can tow the Queen Mary with that rig" (or something to that effect).
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Old 06-23-2009, 08:01 PM   #7
M Hohnstein
1987 34.5' Airstream 345
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Nice to dream, but that drive train requires computer controls that you won't find at AutoZone. If any one finds stand alone ECM controls for the application, fill me in.
Rule of thumb, need a complete donor vehicle for such an upgrade.
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Old 06-23-2009, 08:25 PM   #8
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Yes, a totaled donor would be great.
This is good thinking...and to break the 10mpg envelope!
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Old 06-23-2009, 10:38 PM   #9
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Plenty of totalled Silverado HD's around... Well, at least some. Based on my experience towing with our Duramax / Allison truck, I would guess fuel mileage to be around 10.5-11 when not climbing our great SoCal mountains. It is also very simple to boost power up to over 750 lb ft torque. A beefed up torque converter would be a good idea, the rest of the Allison can easily handle it.
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Old 06-30-2009, 08:46 AM   #10
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I too have thought about this. The problem I found is that so much of the plumbing is on top of the motor and I didn't see how it would fit under my dog house without re-fabricating it all. I think I figured the front grill would need to be moved forward about 2 inched. And then the computer with all the safety inter locks. All the dash gauges would need changed and we all know the nightmare under the dash. I've seen it in a older truck, but trucks have more room to work with around the engine.
I bought a DVD with instructions of how to do it. After I look at it good I dropped that idea.
I'd like to find a wrecked 2007 or up N-serial Isuzu truck with the 4 cylinder diesel and 6 speed trany. That thing is short and compact and powerful.
But then as long as the old 454 keeps a going at 6 to 6.5 mpg guess I'll keep putting gas in it.

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Old 06-30-2009, 08:52 AM   #11
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It would be nice to have a duramax. I've looked at the chevy crate HO502. Makes 450 hp @ about 5K and 550 ft lbs torque @ 3500. 480 ft lbs @ 1750. I think that's the way I'm going. Can get one for about 6K, just add carb, exhaust, & distributor. Any good options for a OD tranny that doesn't take a computer? Would a 700R4 hold up?
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Old 07-01-2009, 01:51 AM   #12
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Looks like a 502 would be far simpler than a Duramax conversion. Now, if you could mate an Allison 1000 transmission to the 502, that would be very nice. GM did produce a lot of vehicles with the 8.1 / Allison combo, and it is highly regarded by owners apparently.
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Old 07-01-2009, 06:16 AM   #13
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700R4 is what I use, with a Gearvendors behind that mind you. Converter clutch is toggle switched, it drops RPM only 100/150 rarely lock it. Most of the time putter along @ 2500 in direct/conv. open and GV in OD, 70 mph.
However, the 700 alone is strong enough and if you work with a quality unit it gets the job done just fine.
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Old 07-18-2009, 09:54 AM   #14
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