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STEP 2 CHA DRIVE TRAIN DIAGNOSIS TFTN0201AJ Inspect 4WD System & Transfer CHA0396 OBJECTIVE PERFORMANCE: ? ? ? Be able to describe the outline of the 4WD system. Be able to describe the various 4WD operation systems. Be able to inspect and measure the transfer type TX12. RESOURCES: The following resources have been prepared for this module. ? ? Transfer unit TX12 model General tools and SST (filler gauge, gear pullers and drifts 1

STEP 2 CHA SKILL CHECK ? DRIVE TRAIN DIAGNOSIS TFTN0201AJ Be able to inspect and measure the transfer type TX12. 2

STEP 2 CHA DRIVE TRAIN DIAGNOSIS TFTN0201AJ CONTENTS 1. FOUR WHEEL DRIVE SYSTEM 1 Function of the System 2 System Type 3 Features of 4WD 4 Disadvantages of 4WD System 2. TRANSFER 1 Construction Type of TX12 Transfer 2 Function of Transfer 3 Transmission of Torque (TX12 type 4 Features of Shift Positions 5 Transfer for FF Based Vehicle TARGET Ability to go to an ESM topic destination Ability to describe the outline of the four wheel drive system Ability to describe the function of the transfer system Here’s what you do . . . . (1 6 Gear Component Inspection (TX12 model type 7 Inspection Points Ability to understand the measurement and inspection points of the transfer system Here’s what you do . . . . (2 3. VISCOUS COUPLING 1 General Description 2 Center Differential Ability to understand the viscous coupling system SKILL CHECK If you feel confident about your knowledge and skills of these tasks, you can proceed to the next module. Ask your course instructor for guidance. 3

STEP 2 CHA DRIVE TRAIN DIAGNOSIS TFTN0201AJ 1. FOUR WHEEL DRIVE SYSTEM 1 Function of the System The four wheel drive system is a system that delivers the engine torque for both the front and rear wheels. It is generally combined with a transfer mechanism. Engine torque distributed for the front and rear wheels can provide better driving performance, stability and drivability, especially on slippery roads. The difference absorption of the rotation speed between the front and rear wheels, which

occurs when cornering due to the difference of the front and rear wheels, is eliminated using a differential function and a drive train partition function. 2 System Type

CLASSIFICATION The driving system of a 4WD vehicle is divided into two categories, part-time 4WD and full-time 4WD. Moreover, the full-time 4WD is classified into two types by the torque distribution system between the front and rear wheels. Part-time 4WD 4WD Full-time 4WD Variable torque distribution type (ALL-Mode 4WD CHA0397 Fixed torque distribution type PART-TIME 4WD 2WD (Rear wheel drive 4WD (All-wheel drive Front differential ENG. T/M T/F Rear differential Front differential ENG. T/M T/F Rear differential CHA0398 4

STEP 2 CHA DRIVE TRAIN DIAGNOSIS TFTN0201AJ CHA0400 Features With the part-time 4WD system, a vehicle is normally driven by two front or rear wheels. As necessary, the 4WD system can be selected by the shifting lever or a switch. Torque distribution Engine torque is always distributed in a fixed ratio to the front and rear (mostly in the 50:50 ratio. Torque distribution is proportional to the dynamic weight distribution on the front and rear tires if all four tires are on the road surface and have the same frictional coefficient. Even if one of the front or rear tires slips, the same engine torque as in the normal condition is transmitted to the other tires and the vehicle gets the same traction based on each tire grip condition. FULL-TIME 4WD Viscus coupling Center differential gear Viscus coupling Front differential gear ENG. T/M T/F Rear differential gear Viscus coupling CHA0400 5

CHA0401

Fixed torque distribution type

With the full-time 4WD system, a vehicle is always driven by all four wheels. This type generally has a center differential system that distributes the engine torque to the front and the rear wheels to absorb the difference between the front and rear wheel rotations. Some models adopt a viscous coupling as a limited slip differential to maintain traction at all times, contributing to better stability when one of the front or rear, or right or left drive wheel slips on a rough road or slippery road.

Variable torque distribution type

Engine torque is distributed in a variable ratio to the front and rear wheels according to the road and/or driving condition.

ALL-Mode 4WD

The 4WD control unit applies to drive the front axle as required via the multiple disc clutch installed in the transfer unit. When the system is set in the AUTO mode, the front and rear torque distribution is operated by hydraulic pressure or electromagnetism and