4spd vs 6spd Allison question.
If I can find 2007 Chev/GMC 3500 with the 8.1 I would like to think about picking one up. I drive my 2002 by the tach, 65 mph=2100 rpm. That seems to be the sweet spot for best mileage. I know I am...
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It's a big block gasser. Mileage is going to s uck equally regardless of what slushbox is hooked to the back of it.
Only place you might pick up a smidge of gas mileage is haulin arse, bobtail, the 2nd OD of the 6 speed may give you a bit of a bump with a few less rpms, but at that speed you're burnin gas like it's free anyways.
Now, to get the Alli over the 4L80 whatever it is, is a big deal if you plan on keeping the truck. 5 or 6 speed. I would be more worried about the miles and condition of an old truck not whether it has the double OD.
Only place you might pick up a smidge of gas mileage is haulin arse, bobtail, the 2nd OD of the 6 speed may give you a bit of a bump with a few less rpms, but at that speed you're burnin gas like it's free anyways.
Now, to get the Alli over the 4L80 whatever it is, is a big deal if you plan on keeping the truck. 5 or 6 speed. I would be more worried about the miles and condition of an old truck not whether it has the double OD.
