2Sliding Gear Transmission Old school, used from late 1800’s to 1940’s?Has two or more shafts in parallel with sliding spur gears.
3Sliding Gear Transmission If either gear is rotating, shifting is difficult and gear “clashing” will result.Some manufacturers may still have a sliding gear for reverse.
4Collar-shift Transmission Has two parallel shafts with gears in constant meshThese “collars” slide on a hub that is splined to the output shaft, thus transferring power.Gear “clashing” will occur if the gear speeds are not matched by double clutching.
5Double ClutchingThe shifter, rather than going straight to the next gear, makes a stop in neutral and then the clutch is released.This is to allow the engine to slow down (or with a tap on the gas, speed up when downshifting) so the transition into the next gear is much more smooth.The driver then depresses the clutch again and completes the shift into the target gear, and finally the clutch is released again, putting the car back into gear.
7Synchromesh Transmissions Gears are in constant mesh and are collar shiftedAll forward gears are of a helical design
8Synchromesh Transmissions Collars are equipped with synchronizersSynchronizers eliminate the need to equalize gear speeds before engagementUsed on all current models of cars – may use a spur gear for reverse
9Synchromesh Transmissions Engine torque is applied to the input shaft (clutch shaft) when the clutch is engaged.The input shaft is fitted with a gear (input gear or clutch gear)
10Synchromesh Transmissions The front of the output shaft is machined to accept a bearing that fits into the input-shaft.The different speed gears (1st, 2nd, 3rd 4th, etc.) rotate on the main shaft.
11Synchromesh Transmissions Parallel to (below or beside) the input and output main shaft is the counter shaftThe counter shaft is fitted with different sized gears.
12Synchromesh Transmissions All of these gears are in constant mesh with the gears on the output shaft except …One gear is in constant mesh with the input shaft gear.
13Synchromesh Transmissions Gear changes occur when the selected gear is connected to the output shaft.This is accomplished by locking a collar onto the selected gear.The collars are moved by shift forks.
14SynchronizersBring components that are rotating at different speeds to one synchronized speedThe four types of synchronizers are:Block (most common type used today)Disc and platePlainPin
15Block Synchronizer Assembly HubSleeveBlocking ringInserts or spring-and-ball detent devices
16Synchronizer Hub The hub is is internally splined to the mainshaft The inserts slide back and forth in slots on the hub.Some inserts use a ridge to detent the slide with an internal groove on the sleeve.
17Synchronizer InsertOther inserts are of a ball and spring design
18Synchronizer Sleeve The sleeve surrounds the synchronizer assembly Internal splines mesh with the outside splines of the hubThe sleeve is internally grooved perpendicular to the splines to catch the ridge of the insert
20Synchronizer SleeveThe outside of the sleeve is also grooved to accept the shift fork
21Blocking RingsBronze or brass blocking rings are found at the front and rear of the synchronizer assembly.
22Blocking Rings …are notched to accept the insert keys on the hub. Thus the blocking ring and hub turn at the same speed.
23Blocking RingsBeveled dog teeth are found on the driven gear and the blocking ring. These are used for alignment during shifting.The inside of the blocking ring is shaped like a cone to mate with the conical shoulder of the driven gear.
24Blocking RingsThe inside of the blocking ring’s surface contains sharp grooves.These grooves disperse oil to maximize friction between the ring and gear.
26Synchronizer Operation First, the sleeve is moved toward the gear by the shift lever and engages the hub assemblySecond, the movement of the sleeve causes the inserts to press the blocking ring onto the cone of the gear
27Synchronizer Operation Third, when the components reach the same speed, the synchronizer sleeve slides over external dog teeth on the blocking ring and over the dog teeth of the speed gear’s shoulder. This action locks the gear to the main shaft.
28Advanced Synchronizer Designs New materials are being introduced for blocking rings including powdered and organic materials.Manufactures are also using double and triple cone designs to maximize friction and reduce wear.
30Transmission Types Three-speed transmission Third gear is direct drive (1:1 ratio)They are rarely used todayFour-speed transmissionFourth gear is direct drive (1:1 ratio)The additional speed ratio is usually between first and second gearA third hub and sleeve assembly is added to provide for reverse
31Transmission Types Five-speed transmission a four-speed transmission with an overdrivehelps increase fuel mileage and engine lifeSix-speedFound on performance cars
32Transmission Types Overdrive units: Popular before advent of four-, five-, and six-speed transmissions
40Transmission Operation Power flow in neutralThe input shaft drives the counter shaftAll of the gears on main shaft rotateThe synchronizers are not engaged with any gearNo power is transferred to the output shaft
41Power flow in first gear The power enters the transmission through the input shaftThe first/second synchronizer sleeve is engaged with the first gear dog teethThe power is transferred from the input shaft, through the countershaft, and up to the first gearThe first gear drives the output shaft
42Power flow in second gear The power enters the transmission through the input shaftThe first/second synchronizer sleeve is engaged with the second gear dog teethThe power is transferred from the input shaft, through the countershaft, and up to the second gearThe second gear drives the output shaft
43Power flow in third gear The power enters the transmission through the input shaftThe third/fourth synchronizer sleeve is engaged with the third gear dog teethThe power is transferred from the input shaft, through the countershaft, and up to the third gearThe third gear drives the output shaft
44Power flow in fourth gear The power enters the transmission through the input shaftThe third/fourth synchronizer sleeve is engaged with the fourth gear dog teethThe power is transferred from the input shaft to the fourth gearThe fourth gear drives the output shaft
45Power flow in fifth gear The power enters the transmission through the input shaftThe fifth gear synchronizer sleeve is engaged with the fifth gear dog teethThe power is transferred from the input shaft, through the countershaft, and up to the fifth gearThe fifth gear drives the output shaft in overdrive
46Power flow in reverse gear The power enters the transmission through the input shaftThe reverse gear synchronizer sleeve is engaged with the reverse gear dog teethThe power is transferred from the input shaft, through the countershaft, through the reverse idler gear, and up to the reverse gearThe reverse gear drives the output shaft in reverse