Gear Swap vs. Fuel Economy

[DirtyD]

RPMs will go up obviously.

These cars have a sweet spot for hwy MPG around 1800-2000 RPM.

For example:

285/35/19 rear tire on your car currently turns 1904 RPM @ 70 MPH in 6th gear on the 6R80.

If you upped your rear gears to 3.55, you would turn 2146 RPM, theorectically, at the same MPH.

3.73s would be a big jump and your hwy MPG would suffer, as you are now over 2255 RPM. You would probably lose 1-1.5 MPG on the highway, but city may go up a little bit.