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How much will this affect my mileage on a 04.5 crew cab 4X4?

Now the truck has 3.73 and I get about 15-16mpg average. I have an AFE 4" exhaust and a quadzilla tune set on 75hp for the winter. At 70mph, I'm usually running 2200-2300rpm. Will the 3.42 gear set drop that down enough to make a noticable mileage difference? I never tow anything over 10,000lbs and usually only tow a few thousand at a time. I'm sure with the amount of torque this thing has it'll have no problem pulling with that gear set.

Thanks
 

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3.73 to 3.42 would be roughly a 150 rpm drop, the 6 speed I think gives you around a 200 rpm drop.

couldn't tell you if either one would make substantial difference in mpgs. In either case you're looking at a high cost to do it. Would take a long time to recoup.
 

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If you want to try just put on 285/75/16 tires. It drops the rearend ratio to a 3.42. I have this setup and cant really tell to much difference. You will tell a very slight difference in power as your turning bigger tires. I tow everyday with this setup and still get my norm 7-8 mpg :D
 

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Don't go looking for major mileage increase's through gears or any other add on, maybe a1 mpg or so, not worth the money spent, you will never recover the costs., You may be better off buying a small car to drive when the truck is not needed..
 

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I agree as said above, my "new" 265's have the RPM at 2k even at 72-73mph, the rpm actually changed going from bald tires to the new more aggressive tire due to extra tread depth. Changing tire size would be the cheaper route to go with, you have to buy tires sooner or later so spend the extra $ on a little larger tire when it is time. I personally didnt see a big difference in milage, the only thing that i have found for better milage is the right foot modification.
 
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