HV-Maxx 6.5/4.5?

[mwe-maxxowner]

Have you done the fan mod? 12/72 may prove to be a little too high gearing with the hv unless you've lightened your truck some. If you've done the fan mod (from traxxas forums, basically you have a 12 volt fan in place of the stock novak fan on the esc, and overvolt it by wiring it to the full 16.8 volts, and you can also put an 80mm cpu fan blowing directly on the motor, this allows you to safely gear much higher.)