Spider Gears
A set of small bevel gears inside a differential that allows the drive wheels to rotate at different speeds during cornering.
Spider gears (also known as pinion and side gears) are small bevel gears housed inside the differential carrier case. Their crucial role is to allow the left and right drive wheels to rotate at different speeds when the vehicle turns a corner.
When driving in a straight line, the spider gears do not rotate relative to each other; they spin together as a unit to drive both axles equally. However, when turning, the outer wheel must travel a longer path than the inner wheel. The spider gears begin to pivot, transferring torque while allowing the outer axle shaft to spin faster than the inner one.
Because spider gears experience high friction and loads, they rely heavily on differential gear oil for lubrication. Worn or chipped spider gears can cause a clicking, clunking, or grinding noise during tight turns. If they break completely, they can lock up the differential or cause a complete loss of power to the wheels.