Fundamental Technology

 Manual Drive Trains and Axles

Introduction

An automobile can be divided into four major systems or basic components : 1 the engine, which serves as source of power: 2) the power train, or drive, which transmits the engine’s power to the car’s wheels ; 3) the chassis, which supports the engine and body and includes the brake, steering, and suspension system; and 4) the car’s body, interior, and accessories, which include the seats, heater and air conditioner, lights, windshield wipers, and other comport and safety features.

Basically, the drive train has four primary purposes: to connect and disconnect the engine’s power to the wheels, to select different speed rations, to provide a way to move the car in reverse, and to control the power to drive wheel for safe turning of the automobile. The main components of the manual drive train are the : clutch, transmission, differential, and drive axles ( figure 1-1). The exact components used in vehicle’s drive train depend on whether the vehicle is equipped with front-wheel drive, rear-wheel drive, or four-wheel drive.

Today, most cars are front-wheel drive ( FWD). Power flow through the drive train of  FWD vehicles passes though the clutch or torque converter, through the transmission, and then moves to front differential, the driving axles, and onto the front wheels. The transmission and differential are housed in a single unit ( figure 1-2) called a trans axle.

Some large and many performance cars are rear-wheel drive (RWD). Most pick-up trucks and many SUV's are also RWD vehicles.  Power flow in a RWD vehicle passes through the clutch or torque converter, transmission, and the drive line ( drive shaft assembly ). Then it goes through the rear differential, the rear-driving axles, and onto the rear wheels.

Four-wheel drive ( 4WD ) or all-wheel drive (AWD) vehicles combine features of both rear- and front-wheel drive systems so power can be delivered to all wheel all the time or when the conditions or driver selects two-wheel or four-wheel drive. Normally, a 4WD pi Normally, a 4WD pi Normally, a 4WD pickup or full-size SUV has 4WD; the drive train is based on a RWD vehicle modified to include a  front drive axle and transfer case.  When a smaller SUV or car has AWD or 4WD, the drive train is modified system. Modification include a rear drive axle and assembly that transfers some of the engine’s power to the rear drive axle.

There are two sets of gear in the drive train: the transmission and the differential. The transmission allows the gear ratio to change and the differential unit changes the power output from the transmission and allows the drive wheels to rotate at different speeds during turns; this prevents tire scuffing. Through the use of different gear ratios, torques is multiplied.