Quote:
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.
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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.