The internal ratio of the TT-01 gearbox 2.6.
Your final drive ratio is: Spur divide by Pinion times Internal Ratio.
The standard TT-)1 gearing 61T Spur with 19T Pinion
Final Drive Ratio is 61/19*2.25 = 8.35
High FDR = Quick accelleration, less top speed
Low FDR = Slower acceleration, higher top speed
Cheers
Kevin