More factors besides low gear + axle, which is why some PG trans work well.
AT: add the stall ratio, stall speed, launch RPM (crankshaft inertial mass), and converter-flex plate stored inertial mass.
MT: add the launch RPM and clutch-flywheel-pressure plate stored inertial mass.
If the total is too high the car is not repeatable or violent on launch.
Torque multiplication. Which is why auto trans low gears will be ~1.80 to 2.70 and manual trans will be very high 2s and more commonly low to mid 3s.
