CHAPTER 63: POWERPOINT LESSON

Use the textbook to define these Technical Terms:

1. Backup Light Switch-

2. Countershaft-

3. Electronic Speedometer-

4. Gear Backlash-

5. Gear Ratio-

6. Gear Reduction-

7. Main Shaft-

8. Manual Transmission-

9. Overdrive Ratio-

10. Shift Forks-

11. Synchronizers-

Use the textbook to answer these discussion questions:

1. Identify and define all the major parts of a manual transmission.

Read the chapter summary below:

Summary:

■ A manual transmission must be shifted by hand to change the amount of torque going to the other parts of the drive train.

■ A transaxle combines both the transmission and the differential into a single housing. It is commonly used in front-wheel-drive vehicles.

■ The basic parts of a manual transmission include the input shaft, transmission gears, synchronizers, shift forks, shift linkage, gear shift lever, output shaft, and transmission case.

■ A manual transmission is designed to change the vehicle’s drive wheel speed and torque in relation to engine speed and torque.

■ Gears are used to transmit turning effort from one shaft to another.

■ A gear ratio is the number of revolutions a drive gear must turn before the driven gear completes one revolution.

■ First (low) gear has a high gear ratio and produces more torque. High gear has a low gear ratio and produces very little torque.

■ Manual transmissions commonly use two types of gears: spur gears and helical gears.

■ The moving parts in a transmission are lubricated by splash lubrication, typically using 80W or 90W gear oil in a manual transmission.

■ Bearings reduce the friction between the surfaces of rotating parts in the transmission.

■ The transmission case supports the transmission bearings and shafts, and provides an enclosure for gear oil.

■ The extension housing encloses the transmission output shaft and holds the rear oil seal input shaft.

■ A manual transmission normally has four steel shafts mounted inside its case: an input shaft, a countershaft, a reverse idler shaft, and an output shaft.

■ The transmission output shaft, also called main shaft, holds the output gears and synchronizers.

■ Transmission gears can be typically classified into four groups: input shaft gear, countershaft gear, reverse idler gear, and output shaft gears.

■ A transmission synchronizer has two functions: it prevents the gears from grinding or clashing during engagement and locks the output gear to the output shaft.

■ The shift forks fit around the synchronizer sleeves to transfer movement to the sleeves from the gear shift linkage.

■ Transmissions with more forward speeds provide a better selection of gear ratios for improved acceleration.

■ In neutral, all the synchronizer sleeves are located in the center of their hubs and no power is transmitted to the output shaft.

■ The overdrive gear keeps engine speed down at highway speeds to increase both fuel economy and engine service life.

■ An electronic speedometer uses a transmission output shaft speed sensor to operate the dash instrumentation.

■ Several sensors and electric switches may be mounted on manual and automatic manual transmissions.

■ Late-model automated manual transmissions use computer-control and electric solenoids or servo motors to actuate the large gearbox.