cat sx2
 

The spur gear and the motor pinion are bare so stones and other dirt could get into it and cause the spurgear to become bald, is there a cover or something which could stop this happening as it is inevitable it will happern?

Only protection it has is the body and undertray. Make sure there a good snug fit together and use good velcro? Other than that try and avoid gravelly areas.:confused:

pretty much all modern competition 4wd cars are like this. with the shell fitting properly around the undertray, you really shouldn't have an issue.