easiest way is to add some final drive ratios (less calculation headache)
in the *_Gears.ini to the section [FINAL_DRIVE].
just take a look at existing files, to see how it works.
you also need to enable it in the *.hdv:
FinalDriveSetting=3 // indexed into GearFile list
the FinalDriveSetting is pointing to the default final ratio in the setup screen (index starts at 0)