174 Manual Drive Trains and Axles Copyright by Goodheart-Willcox Co., Inc. Input shaft Fifth Output shaft 5th gear synchronizer moves into engagement with 5th gear Figure 8-36. This is one version of a 4-speed transmission with a floor shift. (General Motors) Fifth Gear In fifth gear, the input shaft main drive gear turns the countershaft gear, reversing direction, Figure 8-35. The fifth gear synchronizer outer sleeve moves forward. This engages the fifth gear with the counter gear. Since the fifth gear is already in mesh with a gear on the output shaft, the synchronizer move- ment locks together the counter gear and the output shaft. The difference in gear sizes results in a 7:1 gear ratio. Manual Transmission Designs Today, there are many manual transmission designs for rear-wheel drive vehicles. Transmissions that have more forward speeds provide a better selection of gear ratios. Extra gear ratios are needed for the smaller, low-horsepower, high-efficiency engines of today. Some of the most common transmissions are discussed in the following section. 4-Speed Transmissions The 4-speed transmission has four forward gears. These transmissions were the high-performance models on cars in years past. Today, 4-speeds are still occasionally used. Older 4-speeds usually had external linkage. The link- age on newer models is usually internal. Figure 8-36 shows a common 4-speed transmission. 5-Speed Transmissions The 5-speed transmission resembles a 4-speed, Figure 8-37. These transmissions have five forward gears. Fifth gear is usually overdrive. Linkage and case materials are similar to the 4-speed. It is always used with a floor shift. Many 5-speed transmissions were created from exist- ing 4-speeds by adding extra gears on the countershaft and output shaft. 5-speed transmissions are popular because of the improvement in gas mileage with the overdrive gear. Figure 8-35. In fifth gear, the fifth gear synchronizer assem- bly moves forward into engagement with the fifth gear on the countershaft. Power flows through the input gear, fifth gear on the counter gear, fifth gear synchronizer assembly, and fifth gear on the output shaft. (Borg-Warner) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 28 27 32 33 34 1. Drive gear bearing retainer 2. Seal 3. Snap ring 4. Drive gear bearing 5. Drive gear 6. Stop ring 7. 3rd & O/D speed clutch assy. 8. Stop ring 9. Overdrive gear 10. Second gear 11. Stop ring 12. 1st & 2nd speed clutch assy. 13. Stop ring 14. First gear 15. Rear main bearing 16. Extension housing 17. Vent plug 18. Mainshaft 19. Retainer clip 20. Speedometer gear 21. Rear oil seal 22. Reverse idler gear 23. Reverse idler gear bushing 24. Reverse idler shaft 25. Snap ring 26. Woodruff key 27. Thrust washer 28. Countershaft roller bearings 29. Countershaft 30. Countershaft gear 31. Countershaft sleeve 32. Expansion plug 33. Snap ring 34. Drive gear roller bearings