Modern Automotive Technology PowerPoint for by Russell Krick Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

Chapter 59 Drive Shafts and Transfer Cases

Contents Drive shaft assembly Drivelines Transfer cases

Connects the transmission output shaft with the rear axle assembly Drive Shaft Assembly Connects the transmission output shaft with the rear axle assembly

Components Slip yoke Front universal joint Drive shaft Rear universal joint Rear yoke

Functions Sends turning power from the transmission to the rear axle assembly Flexes and allows vertical movement of the rear axle assembly Provides a sliding action to adjust for changes in driveline length Provides smooth power transfer

Operation The transmission output shaft turns the slip yoke The slip yoke turns the front universal joint, driveshaft, rear universal joint, and rear yoke on the differential

Driveline Flex Universal joints let the driveline flex as the rear axle moves up and down

Slip Yoke Splined to the transmission output shaft Allows for changes in driveline length by sliding in and out of the transmission The outer diameter is machined smooth, providing a bearing surface for the bushing and oil seal in the transmission

Slip Yoke

Drive Shaft Hollow steel tube with permanent yokes welded on each end Very strong and light Lightweight units may be made of thin-wall aluminum with longitudinally aligned graphite fibers for added strength May be single-piece, or two-piece

Typical drive shaft assembly

Drive Shaft Balance In high gears, the drive shaft turns at the same speed as the engine The shaft must be accurately balanced The shaft is rotated on a balancing machine at the factory Steel balancing weights are welded to the shaft to reduce vibration

Drive Shaft Balancing Weights

Vibration Damper The drive shaft may be equipped with a large, ring-shaped weight mounted on rubber Helps keep the shaft turning smoothly by absorbing torsional vibration

Universal Joint Swivel connection capable of transferring a turning force between shafts at an angle to one another Made of two Y-shaped yokes, connected by a cross Bearings on each end of the cross allow the yokes to swing into various angles while turning

Universal Joint

Types of Universal Joints

Cross-and-Roller

Cross-and-Roller Cardan universal joint Most common type of joint The bearing caps are held stationary in the drive shaft yoke The roller bearings reduce friction The cross is free to rotate inside the caps and yokes

Several methods are used to retain the bearing cap in the yoke Bearing Cap Retention Several methods are used to retain the bearing cap in the yoke

Cross-and-Roller Drive Shaft Assembly

Constant Velocity Joint A cross-and-roller joint tends to accelerate and decelerate during each revolution, setting up torsional vibrations A constant velocity joint has two cross-and-roller joints connected by a centering socket and center yoke By using two joints, the output shaft speed fluctuations are counteracted

Constant Velocity Joint Speed changes at the output of the first joint are offset by speed changes at the other joint

Constant Velocity Drive Shaft

Ball-and-Trunnion Joint Constant velocity design Eliminates shaft speed fluctuations Allows for slight length changes in the driveline

Center Support Bearing Holds the middle of a two-piece drive shaft Bolts to the vehicle’s frame or body Common on pickup trucks and large vehicles with long wheel bases The rubber mount prevents noise and vibration from transferring into the passenger compartment

Center Support Bearing

Center Support Bearing

Two main types—Hotchkiss driveline and torque tube driveline Drivelines Two main types—Hotchkiss driveline and torque tube driveline

Hotchkiss Driveline An exposed drive shaft operates a rear axle assembly mounted on springs Most common type of driveline Universal joints are used at both ends of the drive shaft Cross-and-roller universal joints are most commonly used

Torque Tube Driveline Uses a solid steel drive shaft enclosed in a large hollow tube Only one swivel joint is used at the front The rear of the torque tube is a rigid part of the rear axle housing

Transfer Cases Used to send power to both the front and rear axle assemblies in a four-wheel-drive vehicle Mounted behind, and driven by, the transmission Two drive shafts run from the transfer case, one to each drive axle

Transfer Case

Four-Wheel Drive versus All-Wheel Drive Four-wheel drive has a transfer case separate from the transmission drive ranges such as 2H, 4H, and 4L are provided All-wheel drive has the transfer case included as part of the transaxle

Four-Wheel Drive versus All-Wheel Drive

Transfer Case Construction Constructed much like a manual transmission uses shift forks, splines, gears, shims, and bearings Made of cast iron or aluminum Filled with lubricant (oil) that cuts friction

Transfer Case Construction

Transfer Case Ranges Two-wheel drive, high range (2H) normally provides a gear ratio of 1:1 Four-wheel drive, high range (4H) Four-wheel drive, low range (4L) normally provides a gear ratio of approximately 2:1

Power Flow

Two-Wheel Drive (High Range) Provided for normal driving when four-wheel drive is not needed Torque flows from the input gear to the locked planet gears and ring gear, which rotate as a single unit Torque is transferred to the main shaft through the planet carrier Power flows out the rear yoke

Four-Wheel Drive (High Range) Torque flows through the input gear, the planet gears, and ring gear as in 2H The sliding clutch is shifted into the main clutch gear Torque flows through the drive chain, to the front output yoke, to drive the front axle assembly Both axles drive the vehicle

Four-Wheel Drive (Low Range) Torque transfer is almost the same as in 4H The ring gear is shifted forward into the lock plate, holding the ring gear stationary The planet gears walk inside the ring gear, producing a gear reduction

All-Wheel Drive Does not use a conventional transfer case Designed for a front-wheel-drive transaxle or a transmission The transmission or transaxle is modified to allow power flow to the front and rear drive axles

All-Wheel Drive A fluid coupling controls the power split to the front and rear axle assemblies