If you have a crunchy noise coming from the gearbox when you put the power down on a straight or exiting corners the gear mesh has slipped apart.I had this problem on my tamiya cars using gear diffs and the fix is easy.In the gearbox you have a 5x14 shim behing the gear,you can either put in 1 or 2 more of these but then you need to buy the rebuild kit(14.99)or get a header card from some parts (carboard)and cut one out,regrease your diff and its solved,being a tool maker i made mine out of brass about .3 mm thick,hope this helps anyone .
