Copyright Goodheart-Willcox Co., Inc. Heavy Equipment Power Trains and Systems 598 • Final drives provide one last speed reduction and torque multiplication before propelling the drive wheel or track sprocket. • A final drive can be integrated with an axle housing or can be a stand-alone component in its own housing. • Inboard final drives can have a planetary gear set design or a bull-and-pinion gear design. • Outboard planetary final drives can be single reduction or double reduction. • Low-track dozers can use a bull-and-pinion final drive, known as a drop axle. • Caterpillar elevated sprocket undercarriages use single- or double-reduction planetary final drives. • Combines, cotton pickers, cotton strippers, and self-propelled forage harvesters use either bull-and-pinion final drives or planetary final drives. • Skid steers and motor graders use two drive chains to propel tandem drive wheels. • Excavator final drives receive their input from a hydraulic motor and have two or three planetary gear sets. • Skid steer chain drive tension should be checked every 500 hours or once every three months. • Tandem chain drives have their own oil reservoir. • Some outboard final drives can be replaced without the need to split a track or remove a drive wheel. • Some skid steer chains do not have a master link and are removed and installed as a complete chain assembly. • Shims are often used to adjust bearing preload or shaft endplay. • Component failures include wear, fracture, corrosion, and distortion. • Component fracture types include fatigue, brittle, ductile, and combination fractures. Summary Technical Terms abrasive wear adhesive wear asperities beach marks brinelling brittle fracture bull gear combination fracture corrosion wear double-reduction final drive drop axle ductile fracture excavator final drive false brinelling fatigue fracture final drive fretting corrosion harvester final drive horizontal oil level mark impact fracture inboard bull-and-pinion gear final drive inboard final drive inboard single-reduction planetary final drive nonintegrated final drive outboard double-reduction planetary final drive outboard final drive outboard single-reduction planetary final drive overload failure ratchet marks single-reduction final drive spalling stress riser tandem chain drive tensile strength torsional stress fracture true brinelling yield strength