To get 75mph at 1700rpms you'd have to have 38" tires, in which case the weight of the tires would kill your mileage.

Rearend 3.73

1-------2-------3-----4------R
2.45---1.45----1.00--0.69---2.21

Do the calculations yourself.

Gear ratio calculator

I don't believe you especially after 2 posts total.

 

Measure them. The bfg site is wrong compared to my tape measure.

 

Yeah, I only get 2000 RPMs @ 75. Granted I have a G56, but I would still need to be in the neighborhood of 1750 for it to be possible on the 48re. My 40.5s will get me close, but I don't even think that will get me there. I think I figured it out to be right around 1800.

 

so what should i do with my truck to get better gas Miles ???

 

Drive it @ 2K RPM or under, don`t be the first off the light. Look ahead and get off the gas before you need to stop. Run a steady speed and don`t drive around in a hurry. Then you could add a TST, Cool Hose and an Amsoil Nanofiber Drop-In filter. Make sure your tire pressures are up to spec. I run 65 front and 55 rear.

 

The second day we owned this '06 model we went on vacation to San Antonio. I've been driving Dodges for years and know the overhead can lie to ya, So before we left, I topped it off. Drove about 500 miles at 73-74 MPH. Filled back up and put pencil to paper. The truck got an honest 21.6 MPG. On the way back, I ran at 76-78MPH and rechecked it again when we got home. Truck got about 18.8 MPG. I have done alot of checking and rechecking since then and the majic number seems to be 74MPH. At that speed or lower on the highway, it will get 21+, if I get to 75MPH the fuel mileage immediately drops to around 19 MPG. I'm thinking that the fuel map in the ECM is not linear and at that engine speed vs. vehicle speed it is making a substantial fuel map change???? Who knows, but it will get 21+ MPG MUCH better that the 04 HEMI i got rid of. That thing had great pulling power and accelleration after I tweaked it.. But when U put a 32ft. fifth wheel on it, you need a refueling truck with a 4" main line in it to keep the fuel light out!!..

 

GAS miles? How about the next time you need fuel, try filling it up with Diesel and not gas as diesel will give you better mpg

 

very smart..... i'll try to use diesel in my diesel truck...good idea

 

i am not shor what is: TST,Cool Hose ,Nanofiber Drop-In filter