I suppose you can use any shaft size, if the pinion gear and spur gear you use have the same pitch. For that power I dont think so the gears are made of very soft metal. I destroyed my front and rear box ...on the buggy.. and I was running the 6200kv motor with 2S 1800mA lipo. Thats about 45 000rpm but much less power. Check out 3 racing they sell a complete diff that has ball-bearings... waiting for the front one allready have 1 in the back and no problems yet.
What kind of assessment is it possible to write about a factory component? The car is a very good little construction for his price. My small son's smile denotes everything when he travels by car with him. I ordered the spare parts because everything is available at a renowned distributor 3x for this much money.the