I bought the truck used and I am trying to figure out if it still has the stock gearing.
Would like a little bit better mileage is possible, but anyways I was curious about what RPM you Guys and Gal's are running at 70.
I run at just under 1750 RPM at 70. And get an average of just under 13 MPG but it is mostly city, However oddly enough I don't get much better on the freeway.
Here is a posting response from a while back with someones elses question about gearing
If I know your tire diamter and RPM at 60, I can probably figure for you.
To calculate at 60MPH:
Multiply tire diameter by 3.14159 (PI) You: 38 inch tiresX3.14159=119.38 inches (tire circumferance)
Divide Tire Circ by 12 (circumferance in feet of tire) Yours is 9.94
5280 (feet per mile) 5280 divided by 9.94 or 5280/9.94= 531.18 tire revs per mile
531.18X 4.30(your axle ratio)= 2282
2282 x trans ratio= engine rpm's at 60MPH
2282X.712(O.D.)= 1624 engine RPM's
2282x 1.0 = 2282 RPM's in direct drive (gear before over drive)
So...1624 RPM's at 60MPH in overdrive
I'm not calculating RPM's at 65MPH because I've had a few beers and I might hurt my brain!
Will work on though!
Site with Ford trans ratios
Ford Motor Company Transmission Gear Ratio's
not to hyjack and post with 7.3 readings. but had to comment on the gearing difference. i would think that if doing 70 gets you 1750rpms wouldnt that make the mpgs go up? cause mine isnt like that.
not really... if the RPM are too low then the motor has to work harder to keep the speed...
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