Often neglected and often needing attention, these gears fit inside the differential of all Minis. The spider gears transmit all the load from the ring and pinion gears to the axles. The gear faces are very hard and not likely to have severe wear but the inside of the gear that rides on the pinion shaft will most like be worn oblong. "Torque" steer, the tendency for the car to dart from side to side under changing speeds, will often be caused by a worn out differential. New spider gears are an important part of the remedy to this problem.