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Downgrading from an 8.1 to a 6.0

desertrat67

desertrat67

Hawk Driver
Joined
Jul 5, 2001
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Location
Dumfries, VA
Howdy guys,

I have been trying to decide what path to take for a truck. My wife and I would like to get a small to medium sized camper (think no more than 8000 lbs.) to use and I think a 2500 Avalanche would do us fine. Four seats for us and the boys and a small bed for the days I need one. My only concern is the 8.1L engine. I have had a big block before and a 6.0L as well. I would be using the truck as a driver for winter driving and occasionally in the summer on days when riding the motorcycle wouldn't be the best option(having to carry shit or pick things up for work, etc.) and do not like the idea of getting 10 mpg again. Our '05 2500 HD was getting 13-14 average (NV4500 and 4.10 gears) with the 6.0L and had nice power in that truck and I know the newer ones made a little more power. I know selling the 8.1 wouldn't be hard, but how difficult is it to swap a 6.0L in place of the 8.1L? Is it only a matter of new motor mounts and the correct ECU for the engine, or would there be a lot more entailed in the swap?
 
I don't think the effort is worth 3mpgs... Especially since the 6.0 is gonna barely do better mpg wise loaded whereas it pretty much doesn't make a difference with the 8.1.

As far as swapping goes don't forget you're talking about switching the Allison 1000 for a 4l80 or 6l80 unless you're starting with an avalanche for sure.
 
I say run the 8.1 until you have a specific reason to swap but in my case it would be more of an ability to preserve cash flow, lol
 
If you want four doors and a 6.0, just buy that. I think would be a waste of time and money to swap a bigger engine for a smaller. Use that money to buy a nicer crewcab. Plus the big block will pretty much the same fuel mileage no matter what you're doing with it.
 
Stomis said:
I don't think the effort is worth 3mpgs... Especially since the 6.0 is gonna barely do better mpg wise loaded whereas it pretty much doesn't make a difference with the 8.1.

As far as swapping goes don't forget you're talking about switching the Allison 1000 for a 4l80 or 6l80 unless you're starting with an avalanche for sure.
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The Avalanche had the 4L85E in it, so that is something that would not have to be touched. As for the mileage vs cost of swapping, I could make back what I spend on a 6.0 with the sale of the 8.1, so the overall cost wouldn't be too much, I would think. I guess I could get a small beater to drive for my winter and occasional summer commuter and ot care what mileage I get when I use it to tow.

KirsL said:
If you want four doors and a 6.0, just buy that. I think would be a waste of time and money to swap a bigger engine for a smaller. Use that money to buy a nicer crewcab. Plus the big block will pretty much the same fuel mileage no matter what you're doing with it.
Click to expand...

Kris, I like the Avalanche and the 2500 only came with a 8.1L, hence the reason to change. I guess the 8.1L wouldn't be all together that bad if it was only driven infrequently.

If only GM hadn't been dumb and offered the 07+ Avalanche in a 2500 like they did the Suburban. And if they had just put that damn 4.5L Duramax in the 1500 and 2500LDs instead of shelfing it.

Thanks for the feedback.
 
Well lots of people have been hoping for the baby duramax. GM is just being stupid by not doing it. The Avalanche is a nice platform. If you're thinking a getting a beater to drive anyway. Then I'd go with better towing power of the big block, but that's me.
 
my 99-6.0/4L80 has consistently gotten 11.5 rural driving, maybe 13.5 on the highway....empty
I'd stay with the 8.1 too
 
Another vote for the 8.1...cause big blocks simply rule!..
Gas is cheap now too...and I've never regretted having "too much power"...to save even 5 mpg is not worth the effort and expense in my opinion..
I bet the 8.1 might deliver better mpg under certain conditions,like towing,when the 6.0 would have to work harder to maintain the speed and uphills..
 
Yet another vote for the 8.1L. My experience has been they get more or less the exact same unloaded mileage as a 6.0L, but totally kick the 6.0L's butt when towing something as their mileage stays more or less the same while the small block falls way off.
 
my 6.0L/4L80E never got decent gas mileage unloaded, I would never swap out a 8.1L for a 6.0L for that reason.
 
I've towed with small blocks and big blocks.....My current 8.1 is not worth trading when I consider how well it tows. A 6.0 may be able to tow as good on short/light hauls, but I would think that a 6.0 will work much harder to do the same job that the 8.1 does easier and die sooner. There's nothing I love more than passing diesels on a long grade with my gasser when I'm pulling. Yes, I don't pass all of them, but I like to think the ones I do pass have a dumbfounded look on their faces trying to figure out what gas motor just passed them. If you're pulling with the 6.0 that thing is probably working way too hard pulling any hills.

Keep the 8.1 and buy a beater for town. That's my plan.
 
I have the 8.1L Suburban and get around 11-12 MPG on the highway. Towing our double axle trailer/boat, I get 8.5-9.0 MPG going at 75 MPH. I can easily go 80 without straining the engine and I must say, it tows with all kinds of extra strength. To me, it's worth towing with the 8.1 and it does it with ease. Even passing vehicles, no problem. I have 3.73 gears.
 
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