Stripping spur gears is common when running radio control cars. Going hard on acceleration and/or hard on brakes on an RC car will generally cause this to happen, just like a real car. 

They are designed as a give point in the driveline so other more expensive components (like diffs and driveshafts) don't fail so often.
While a stripped spur gear is not covered under warranty on an RC car, the good news is the parts are usually inexpensive so you will be back up and running in no time. 

If you need a replacement spur gear or any other part for your car please contact our Customer Support team with a part number (found in your car manual) and they will get back to you with price and availability.