Chapter 8 Manual Transmission Construction and Operation 165 Copyright by Goodheart-Willcox Co., Inc. Snap ring Sleeve Bearing washer Thrust washer Snap ring Reverse idler shaft Reverse idler gear Needle bearings Thrust washer Blocking ring Inserts Insert spring Outer sleeve Insert spring Blocking ring Splines Spring Ball Oil grooves Inner hub Slots for inserts Output shaft Figure 8-12. This shows the location of the blocking rings in relation to the sleeve and hub assemblies and the mainshaft gears. Note that the parts would actually be closer together than what is shown in this somewhat exploded view. (General Motors) The blocking ring, when fully engaged, fits between the mating gear and the outer sleeve. However, the sleeve does not move into engagement with the teeth on the gear until the ring and gear are brought to the same speed. Synchronizer operation Synchronizer operation is relatively simple. The driver pushes the clutch pedal to disengage the clutch and uses the gearshift lever and linkage to operate the synchronizer outer sleeve. When the outer sleeve is moved toward the gear to be engaged, the internal teeth of the sleeve mesh with the external teeth of the blocking ring. This causes the blocking ring to turn at the same speed as the sleeve, which is turning at output shaft speed. (If the blocking ring is held in place with inserts, it is already turning at sleeve speed.) As the outer sleeve continues to move, it pushes the blocking ring into engagement with the cone surface of the mating gear. The mating gear is unloaded because no engine power is being delivered while the clutch is disen- gaged. Friction between the two surfaces brings the mating gear to the same speed as the outer sleeve and, therefore, to the speed of the output shaft. The ring and cone surfaces become solidly engaged. The sleeve continues its forward (or rearward) movement, and it engages the mating gear with- out clashing. This locks gear, sleeve, hub, and output shaft together. Now, the gear is engaged with the output shaft, and the clutch pedal can be released. Power flows through the gear and on to the rear wheels. Note that direct drive is provided by engaging the sleeve and blocking ring directly with the cone surface on the main drive gear. Also, note that some transmissions use a single sliding gear for low and reverse. The gear is free to 1 2 3 4 5 6 7 8 1. 2-3 synchronizer assembly 2. 2nd speed blocking ring 3. 2nd speed gear 4. 1st speed gear 5. 1st speed blocking ring 6. 1st speed synchronizer assembly 7. Reverse gear 8. Output shaft Figure 8-11. Basic synchronizer components. The inner hub is splined to the output shaft. The outer sleeve fits over the inner hub. Blocking rings allow the sleeve to slide into and mesh with the mainshaft gear without clashing. Spring-loaded inserts and ball keep the sleeve centered on the hub until the shift fork pushes the sleeve on the hub. Note that the helical lines around the output shaft are oil grooves. (General Motors) Figure 8-10. Exploded view shows the parts of the reverse idler gear assembly. The reverse idler shaft is normally locked in place. Thrust washers control endplay. (Chrysler)