This is an optional Traxxas Rear Machined Ring & Pinion Gear (Spiral Cut)
Spiral-cut 37-tooth ring and 13-tooth pinion differential gear sets are CNC-machined from a solid block of steel. The teeth are cut with a slight curve to minimize backlash between gears and maximize tooth traction with more surface area than straight-cut gears. Spiral-cut gears are ideal for high-torque, high-speed, brushless applications.
