I would highly recommend not having any gears on the rear axle, as this creates much friction. If Iām correct, you are using two double AA battery packs? If so, these are very heave and will reduce your over all achieved speed. I would recommend getting one or two buwizz 2.0 batteries. As they have twice the power as LEGO batteries, which is more the reason to remove the gears on the rear axle, or at least use wd40 on them to keep them from melting! This is a good concept, but Iām not sure how well it will work. One last thing, definitely lessen the steering angle, otherwise it will constantly roll over. Wish you luck