Chapter 8 Manual Transmission Construction and Operation 173 Copyright by Goodheart-Willcox Co., Inc. Input shaft 1st and 2nd gear synchronizer moves into engagement with 1st gear Output shaft First Input shaft Third Output shaft 3rd and 4th gear synchronizer moves into engagement with 3rd gear reversing direction again so that the low gear turns in the same direction as the input shaft. Since the outer sleeve of the first-and-second gear synchronizer has been moved rearward, the low gear is locked to the output shaft. The vehicle is in first gear. The difference in countershaft gear and first gear teeth results in a gear ratio of about 3.5:1, and the vehicle accelerates easily. Second Gear In second gear, the input shaft’s main drive gear turns the countershaft gear, reversing direction, Figure 8-32. The countershaft gear turns the second gear on the output shaft, reversing direction again. This double reversal makes the sec- ond gear turn in the same direction as the input shaft. Since the outer sleeve of the first-and-second gear synchronizer has been moved forward, the second gear is locked to the output shaft. The vehicle is in second gear. Note the difference in size between the countershaft and mainshaft teeth in second gear. A typical ratio in second gear is about 2.5:1. Third Gear In third gear, the input shaft’s main drive gear turns the countershaft gear, reversing direction, Figure 8-33. The coun- tershaft gear turns the third gear on the output shaft, reversing direction again. This double reversal makes the third gear turn in the same direction as the input shaft. Since the outer sleeve of the third-and-fourth gear synchronizer has been moved rearward, the third gear is locked to the output shaft. In third gear, the difference in size between the countershaft and second gear mainshaft teeth result in a ratio of about 1.5:1. Fourth Gear In fourth gear, the synchronizer outer sleeve moves forward, engaging the main drive gear, Figure 8-34. This locks the input and output shafts together. This is direct drive, or a 1:1 gear ratio. Notice that the countershaft gear is not used to transmit power in direct drive. This is true of direct drive in any manual transmission. Figure 8-33. In third gear, the 3-4 synchronizer assembly moves rearward into engagement with third gear on the output shaft. Power flows through the input gear, third gear on the counter gear, and third gear on the output shaft, the 3-4 synchronizer assembly, and to the output shaft. (Borg-Warner) Figure 8-31. When the driver selects first gear, the 1-2 synchro nizer assembly moves rearward into engagement with the first gear on the output shaft. Power flows through the input gear, first gear of the countershaft, the first gear on the output shaft, through the 1-2 synchronizer assembly, and to the output shaft. (Borg-Warner) Input shaft Second Output shaft 1st and 2nd gear synchronizer moves into engagement with 2nd gear Input shaft Output shaft Fourth 3rd and 4th gear synchronizer moves into engagement with input gear Figure 8-34. When fourth gear is selected, the 3-4 synchronizer assembly moves forward into engagement with the input shaft. Power flows from the input shaft through the 3-4 synchronizer assembly to the output shaft. This gear bypasses the counter- shaft. The transmission is in direct drive. (Borg-Warner) Figure 8-32. In second gear, the 1-2 synchronizer assembly moves forward into engagement with second gear on the output shaft. Power flows through the input gear, second gear on the counter gear, and the second gear on the output shaft, the 1-2 synchronizer assembly, and to the output shaft. (Borg-Warner)