The only real way to test the setup is to drive ur car on the track.
The obvious "We Weee...." sounds are from the motor.
If you are really, really scare that you might blow up something , Use a Multimeter, connect it to the motor. And check how much the current reading. (hopefully ur instruction will tell you how much current the motor chows)
Just to let you know thou, the higher ratio is used for tight tracks. as i drive around the track like a tank driver