Cummins 3.9L, 5.9L B Series Flywheel Ring Gear, 3978313

Works with 3905831, 4933355, 3914432, 3914431, 3936821 flywheels
Cross Reference 3978313

Note: Some of these flywheel numbers can also use different ring gear numbers depending on the engine serial number. Make sure to measure and count the teeth on your ring gear.

159 Teeth, 15.9 O.D.