Who here daily drives their square body? (long(

[Firebirdjones]

Originally Posted by Rubble

The mileage thing is funny because you can ask 10 different people and you get 10 different answers.Still goes back to my decision to drive an old square for daily driver,how come these newer/new 3/4 ton trucks can't get any better mileage,or any significantly better than a 25-30 year old truck?? My 85 I had 25 years ago would average 13-15 mpg with a 350/400/208 with 31" tires!! Where is all the technology ?????
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That's always been a question in my mind. My fathers 03 3/4 ton 4x4 with the 6.0/4L80 and 4.10 gears averages about 15 mpg for him. Not horrible but not what I would consider all that great for something with fuel injection and overdrive. Everyone thinks the 6.0 should be a gas hog,,,I mean lets face it,,,it's not a big engine,,,it's only 364 cubes, there is no reason for it to be considered a gas hog. It only has 9 cubic inches over the 355 I used to run in my blazer. I now run the same 2004 6.0 engine in my 72 4x4 blazer with a 4L60 and 3.73 gears and get 17/22 city/highway with an optimized tune. I think that's alot of the answer to your question. GM puts such a lazy tune in these things (low timing tables/pig rich WOT AFR's) makes the engines lazy. My neighbors 03 duramax 3/4 ton is getting him 17-18 mpg which doesn't seem all that special to me for a diesel. Again I'm sure there is something left on the table with the tune though. If I can get 14 mpg out of my 79 1 ton with a 502 in it, no overdrive, and 3.73 gears, then there should be potential in any pickup truck out there if optimized properly.

[kwin]

Originally Posted by Firebirdjones

That's always been a question in my mind. My fathers 03 3/4 ton 4x4 with the 6.0/4L80 and 4.10 gears averages about 15 mpg for him. Not horrible but not what I would consider all that great for something with fuel injection and overdrive. Everyone thinks the 6.0 should be a gas hog,,,I mean lets face it,,,it's not a big engine,,,it's only 364 cubes, there is no reason for it to be considered a gas hog. It only has 9 cubic inches over the 355 I used to run in my blazer. I now run the same 2004 6.0 engine in my 72 4x4 blazer with a 4L60 and 3.73 gears and get 17/22 city/highway with an optimized tune. I think that's alot of the answer to your question. GM puts such a lazy tune in these things (low timing tables/pig rich WOT AFR's) makes the engines lazy. My neighbors 03 duramax 3/4 ton is getting him 17-18 mpg which doesn't seem all that special to me for a diesel. Again I'm sure there is something left on the table with the tune though. If I can get 14 mpg out of my 79 1 ton with a 502 in it, no overdrive, and 3.73 gears, then there should be potential in any pickup truck out there if optimized properly.

I think the 4l80e is a part of the reputation for poor fuel economy, compared to the 60 its heavier and requires more energy to turn. I think gearing , tranny and how they are worked is a big part of the reputation for being a pig. Certainly tune helps , I currently get 21 highway in my 91 burb, with everything in palce 6.0 4l60e proper tune and gearing I hope to be closer to 24 mpg. That being said thats not the main reason for the swap.

[Firebirdjones]

Originally Posted by kwin

I think the 4l80e is a part of the reputation for poor fuel economy, compared to the 60 its heavier and requires more energy to turn. I think gearing , tranny and how they are worked is a big part of the reputation for being a pig. Certainly tune helps , I currently get 21 highway in my 91 burb, with everything in palce 6.0 4l60e proper tune and gearing I hope to be closer to 24 mpg. That being said thats not the main reason for the swap.

Yes I agree, the 4L80 is a disadvantage when it comes to fuel mileage. It's a stout tranny, but takes HP to turn it, and it doesn't have as much of an overdrive in it (only .75) compared to the 4L60 with a .70 4th gear. Not alot of difference but if we are getting technical, it's part of the equation.

21 highway from a burb is excellent with that 6.0. I'm getting 22 mpg out of my 6.0 in a 72 4x4 blazer using the 4L60 just as you did. I'm extremely pleased with it.