Which dually - 8.1 vs pre-DEF 6.6?

[Frankenchevy]

Looking for a crew cab dually. As a dedicated dump trailer/equipment trailer vehicle. I read that 06-07 dmaxs are the least problematic. Also read that 03-05 are fine once original injectors are replaced. 8.1 is obviously more simple, but lower fuel economy I’m guessing…and less torque. Which way would you go?

Here’s the dmax. 131k and the won’t budge on the price ($17k). Injectors and turbo replaced at 80k. Leather trim level and clean interior.

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Here’s the 8.1. 122k and second owner since it was a year old. Has the common ABS module issue. Just have to open it up and resolder a couple pins. Cloth interior, but pretty clean. They said they’d take $12k right out of the gate.

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[carfanatic63]

8.1 all day.

 

[bluex]

Honestly if it primary purpose is towing anything over 10k lbs the diesel in a better buy.

 

[Frankenchevy]

8.1 all day.

I just read that 8.1s all consume oil. Is this your experience.

Honestly if it primary purpose is towing anything over 10k lbs the diesel in a better buy.

For longevity’s sake or fuel consumption?

 

[bluex]

For longevity’s sake or fuel consumption?

Just because that's what they are for an are much better at it.

I used to be solidly in the "why does everyone need a big diesel truck" camp. Gas trucks do it just fine. I started towing heavier stuff an it started to make more sense. My gas truck does it sure but it struggles on hills (I'm on the edge of the mountains), gets horrible mileage even empty an just overall feels rougher on the truck. The diesel seems to do it more effortlessly, gets better mileage loaded or unloaded etc.

I don't want another/different truck so it's getting a cummins soon but if I was looking at purchasing something that comes with a decent diesel already (ie not a 6.2/6.5 ) then I wouldn't consider a gasser for a primary towing vehicle. If it was only gonna tow 3-4 times a year then maybe since the cheaper maintenance might be able to offset the fuel mileage.

From your description it sounds like it'll spend more time with a trailer on it than off so that's a no brainer for the diesel in my book.

 

[Frankenchevy]

I have no experience with a modern BBC, so I am not at all aware of their towing characteristics. I am a Cummins guy when it comes to diesels, but I don’t want anything newer than 07. My buddy just dumped $10k into his modern diesel with 100k on the clock. Seemingly minor stuff too. We have a newer Cummins as well, but pretty low hours and mileage.

I’d be open to a dually automatic version of my 04 Cummins or a dually automatic 7.3, but they are considerably more expensive in similar condition. I feel like older people gravitate more towards the IFS of the GM products and you can find them in nice condition for a reasonable price more often. A 130k 04 Cummins as nice as that duramax would be double the price.

 

[legopnuematic]

I don't have any experience with a Duramax personally, but some with an 8.1/6 speed. Not a race truck by any means but pulled good.

Not sure what the mileage was like but I'd imagine high singles low doubles loaded.

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Don't have a picture of it when it was pulling it but that same GMC hauled this dump bed, think it was like 24k lbs total, between truck, trailer, and dump box.

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And there is the legendary 8.1/6 speed truck, over 500k on it and continuing to haul junk around

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Not to say the 8.1 is better than a Duramax, or the other way around, I think both are very capable.

Duramax definitely has some PITA things about it, stuff like the water pump and turbo access, compared to the Cummins platform at least.

 

[bucket]

What is the torque rating on the 6.6?

I have done A LOT of heavy towing with '03, '05, '06 and '07 Duramaxes. They pull good and they are relatively reliable. Fuel mpg in the real world is NOT what all the diesel guys brag about. They have a very finicky pcm and can cause some very annoying driveability issues. They are kind of a bitch to work on. And expensive.

I don't have a bunch of experience with the 8.1 trucks, but I do know that they also pull very well. It is comparable to a stock Duramax. The fuel mileage is definitely worse than the Duramax, but around here, gas is often a full dollar cheaper than diesel. They are much easier to work on, generally.

So my opinion, in short:

Both are designed as 100% tow engines.
Both are designed for 300k mile service.
Diesel is expensive.
Gas is cheap.
Duramax is difficult to work on.
Big block is easy to work on.
Duramax gets OK mpg
Big block gets terrible mpg.

I'd go with whichever truck you like the best, as far as condition, looks and whether or not you will be the one working on it. As long as both those trucks are not hiding anything and neither have a major failure, cost of ownership (including purchase and fuel) will be about the same.

 

[bucket]

Oh, I forgot to elaborate on the finicky Duramax PCM thing. I have no idea how many times I've been pulling a load down the highway and I've lost all power and had to pull off the side of the road, clear random fault codes, then get back along my way. It's always some stupid pidly little insignificant thing that the tuning isn't happy about, so it goes into some kind of limp mode that is basically undriveable. All the trucks too, not just one or two of them.

 

[Frankenchevy]

And there is the legendary 8.1/6 speed truck, over 500k on it and continuing to haul junk around

Any oil consumption as many have reported?

Duramax definitely has some PITA things about it, stuff like the water pump and turbo access, compared to the Cummins platform at least.

The third GEN and earlier Cummins are stupid easy to work on.

 

[Frankenchevy]

Oh, I forgot to elaborate on the finicky Duramax PCM thing. I have no idea how many times I've been pulling a load down the highway and I've lost all power and had to pull off the side of the road, clear random fault codes, then get back along my way. It's always some stupid pidly little insignificant thing that the tuning isn't happy about, so it goes into some kind of limp mode that is basically undriveable. All the trucks too, not just one or two of them.

That would be annoying enough for myself, but with somebody else in the truck, it would be downright problematic. And yes, I will be the one working on them because I have trust issues with mechanics.

 

[Redfish]

I had a 2007 "Classic" with the LBZ Duramax and it was wonderful. The new body style '07s had the first of the DPFs and all the problems that went with them. I never had any codes. My only complaint, ever was that the fuel mileage was not as good as what some folks were saying. I could get 18 on the interstate at best. Towing mpg depended on weight, wind drag and velocity.

I have to say that Duramax was one of the best engine and transmission combinations I have ever used.

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[legopnuematic]

Any oil consumption as many have reported?

The third GEN and earlier Cummins are stupid easy to work on.

No oil consumption that I knew of, but that red truck got parked at some point due to a bad slave cylinder. On those the trans has to be pulled to change them.

The same people that had that red 3500 also have a 2500hd 8.1/Allison that they bought new and I do not recall any mention of using oil.

Agree 100% on working on a Cummins truck. While the Duramax and Power strokes (and the 93-94 7.3 turbo IDI) engines are pretty solid platforms in general, the packaging of a turbo diesel V8 is just ugly compared to an inline engine.