Maxx wont move
Check the following:
Step 1
Make sure the pinion [gear on the motor] is making contact with the spur gear [big gear on the transmission/gearbox]
Step 2
Check that the spur gear has not stripped - if it has - replace it with a steel RRP product. The teeth should be visible.
Step 3
Check the slipper clutch - tighten the nut in the center of the spur gear all the way down then llosen it by about 1/4 turn.
Step 4
Check that the transmission is not stuck in neutral, which may happen when the motor idles too high. Reduce the idling and select reverse on the transmitter. See if the selector shaft in the front of the transmission moves. Select reverse, gas, see if it moves. Select forward and see if it moves.
Step 5
Assuming non the of the 4 steps mentioned helped in resolving this problem, take the MAXX to a hobby shop or someone who knows nitro trucks