Gold pan upgrade
I raced these cars back in the 80's try finding a graphite chassis also MIP made a diff for these which was way better than stock. Another thing you can do is hand file the idler gears and dif gear they will be much smoother and last longer as they were fairly burred up butas one of the previous post said that is the week point. Someone made a metal Idler gear but they never panned out. Good luck