Mechanic Glossary

Differential Ring Gear

The large, circular gear bolted to the differential case that meshes with the pinion gear to transfer power to the wheels.

The ring gear is the largest gear in the differential. It receives torque from the small pinion gear. This changes the direction of drive force by 90 degrees to turn the axles. The ratio between the teeth on the ring gear and the pinion gear determines the vehicle's final drive ratio.

Ring gears are hardened steel to handle extreme engine torque. If the backlash is set incorrectly, the teeth will slip and shear off. A chipped tooth will cause a rhythmic clunking sound that changes speed with the wheels.

Frequently Asked Questions

You will hear a repeating clicking or clunking sound under acceleration. The loose metal chip will quickly destroy the rest of the gears.
Apply gear contact marking compound to the teeth, spin the gears, and examine where the pinion gear contacts the ring gear teeth.
It varies by vehicle. Heavy trucks might use a 10.5-inch ring gear, while passenger cars use smaller 7.5 or 8.5-inch gears.
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