Copyright Goodheart-Willcox Co., Inc. 573 Chapter 17 Final Drives Objectives After studying this chapter, you will be able to: ✓ Explain the purposes of a final drive. ✓ Describe the power flow through integrated inboard and outboard final drives. ✓ List examples of nonintegrated final drives. ✓ Explain the operation of tandem chain final drives used in construction equipment. ✓ Explain the power flow through excavator final drives. ✓ Explain the operation of elevated drives in articulated rubber track tractors. ✓ Describe the methods used for checking final drive oil levels. ✓ Describe the different methods for adjusting skid steer chain drive tension. ✓ Explain the process for replacing skid steer chain drives. ✓ Perform failure analysis on a final drive. H eavy equipment systems multiply torque in several locations, including the torque converter, transmission, differential pin- ion and ring gear, and the final drive. Introduction to Final Drives A final drive is a gearing system that multiplies the machine’s torque and reduces the speed one final time prior to the drive wheel or drive sprocket being driven. Heavy-duty bearings in a final drive support the machine’s load and absorb torque and shock loads. Final drives also serve the following purposes: • Drop the drive’s power flow to a lower axis (traditional dozer). • Elevate the drive’s power flow to a higher axis (elevated rubber track tractor). • Drive tandem wheels through drive chains (skid steers and motor graders). • Change the direction of power flow by 90° (spiral bevel gear set). In a traditional automotive light-duty truck application, the dif- ferential’s spiral bevel ring and pinion gear set is the powertrain’s only final drive. However, most off-highway machines have separate final drives. Off-highway machines may or may not use a spiral bevel gear set. If torque multiplication were provided by the transmission only, the machine would require a much heavier transmission. In addition, stronger shafts would be needed to deliver the power from the trans- mission to the drive wheels or tracks. The use of final drives allows for smaller transmission components (bearings, gears, and shafts) to deliver power to the final drives, where the torque is multiplied one more time prior to driving the wheel or sprocket. Several types of final drive gearing are used on off-highway machines. They include the following: • Spiral bevel. • Bull-and-pinion. • Planetary gears. • Chain drive.