geared motor

[Lil Giants]

So the motor you have pictured is 10RPM? Multiply 3.75 axle ratio = 37.5RPM

2nd gear was a little slow on the junk 740, so maybe you got it right with a bit faster ratio & .7 inch taller tire. Those tires RC4WD too? (I would assume so) very thin side walls, the tires will squat alot without packing adding.

The hinge looks much better, how well it will work will depend on how sharp you turn. Perhaps with your front axle so far ahead of the hinge, you won't need to many degrees angle to turn sharply.