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Running at 75-80 with a truck is never going to get you good mileage no matter what gear you run, IMHO. I have 3.55s w/31" tires on my '92 F350 4x4 and a 5.8L engine. Those gears are barely adequate for my application. RPMs are ~1750 @65 MPH. Granted my truck is heavier and pushing extra drivetrain, but I see no reason to consider anything below 3.55 with any size tire on a truck. One of these days when I win the lottery I can see 4.56s in my future.
I didn't mean that 75-80 was the best speed for fuel economy. I know its not. I just meant that with too low (numerically higher) gears, the rpms will be too high at that speed to get decent milage. I drive at that speed fairly often and most of the time it it to keep up with traffic. I still average 15-16 mpg city/highway weather I do that or not. So, It can't be that bad.
92 F150 Ext Cab XLT compromise of both my tire size i am using is 31x10.5r15 but i am going to go to 33" tires sometime in the future
Don't put bigger tires on if you plan on using the truck to haul a large trailer. In your case 4.10 gears is the starting point and more if larger tires are installed.
hey texas guy 001 and conanski thanks for the great feed back. it has really opened my eyes and my mind as too what gears can be used to still get the best of both fuel and economy. now i am seriously considering the 3.55 or the 3.73. hey texas guy 001 the tire size i am currently running are 245 60 15 front and 275 60 15 rear bfg's. just got the tires about 10 months ago. by the way texas guy 001 and conanski with the tires i have what gears do you both think would be good to run with these tires............thanks again for the great feed back..............
I have never heard of anyone swapping out an 8.8" for a Dana 44, probably because there is no good reason to. They are similar in strength, and while the Dana 44's were available in a few late 70's F-150's, they were never put in trucks from 1980 & up. So it won't be a bolt-in, you will need to move spring perches, shock mounts, etc. Since there isn't much of a strength difference there isn't a reason to go through all that. Plus, you need a VSS for your speedometer to work.
even if i strip the front and rear axles off a 250 and the suspension of both put a load assist airbag system on the rear end put a brake controller and a 7 blade rv trailer electrical setup on it?