The program can NOT replace real world experience... and the real world disagrees with your program...

that program looks like it would be great in a perfect world BUT it does NOT take into consideration aero dynamics and the additional load
the wind resistance adds. For this reason its just the opposite. Even though the 3.55's and 3.92's get a passing grade they also LACK the mechanical advantage to overcome that additional load at speed. I have seen 3-4MPG average INCREAS from going from 3.55 to 4.56 gears. I only gained 300 RPMS...


Hank does that program use the transmission ratios as well? or just rear gearing... Im starting to think that DC used that program to INCORRECTLY choose the best gear for these trucks.

SPEED SAFE, AIR RAM

 

so are 3.55s with 33 hurting my gas mileage? or is that ok

 

You need to take into consideration your transmission overdrive ratio and your rear gear ratio... with that we can do the math to see what would be the best ll round gear. I like to keep the RPMs close to 2,000RPMs at 60mph for overall best performance and fuel economey.

In my 3rd Gen Ram I have a .75 overdrive and 4.56 gears

Trans gear x rear gear = OVERALL GEAR RATIO

.75 x 4.56= 3.42

Now we need to use that OVERALL GEAR RATIO to figure out what the RPMs will be at 60MPH:

SPEED x OVERALL GEAR RATIO x 336 / TIRE HIGHT = RPM

60MPH x 3.42 x 336 / 30" = 2,298RPMs I get 19-20MPG with this combo

With my 20's which are 32.5" tall:

60MPH x 3.42 x 336 / 32.5 = 2,121RPM's I get 18-19MPG with this COMBO

NOW the intresting part is... although my RPMs are lower with the 32" tall tires I get better fuel economey with the 17's which have higher RPMs at 60MPH....

So like I have posted time in and time out... RPMs are not the ONLY factor in fuel ecoomey and the load on the vehicle at any speed has a great effect on fuel economey...

So do the math and let us know what you learn.

SPEED SAFE, AIR RAM