Copyright Goodheart-Willcox Co., Inc. Heavy Equipment Power Trains and Systems 586 A B Track drive sprocket First stage ring gear Second stage ring gear Third stage ring gear First stage planetary carrier First stage sun gear Second stage sun gear Third stage sun gear Second stage planetary carrier Third stage planetary carrier Hydraulic motor Motor housing mounted to track frame Figure 17-22. Excavators can use triple-reduction final drives. A—A side view of an excavator final drive. The hydraulic motor drives the first stage sun gear. The three ring gears are attached to the track drive sprocket. The third planetary carrier is held stationary. B—A cutaway of a final drive. Goodheart-Willcox Publisher Goodheart-Willcox Publisher