I just installed a TankToko metal upgrade kit to the gearboxes of my SU-122 and am truly impressed with the mobility this vehicle now has. The installation was fairly simple once I figured out how to remove the brass collar from the original vinyl drive gear. I used my cordless drill and chucked the collar and it came off no sweat. I used my small vice to put the new collar and gears on the stock parts and voila. The new set up is much noisier than my original T34 but I will work with that now that the suspension doesn't buckle and skip. Who knows, maybe I will add metal tracks?