RE: tire question and 2 speed
You will not always notice the transition of the 2spd, it may be shifting a little early and not really winding out the motor.
This is not a problem or anything, you just may not hear it.
You can hold the car in the air while running, let it hang so that it is free to rock back and forth if it wants to, run it up and you should see it do a little rock when it hits the second gear. Depending on your shift point you may have to run it up slowly.
Dbow