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Manual Transmission Fundamentals

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Presentation on theme: "Manual Transmission Fundamentals"— Presentation transcript:

1 Manual Transmission Fundamentals
Chapter 71

2 Objectives Describe the relationship between gears and torque
Understand the basic types of gears Calculate gear ratios Trace the power flow through three-, four-, and five-speed transmissions Name all of the transmission parts

3 Introduction Manual transmission Used with clutch Transmission
Shifted between gears manually Transmission Used in rear-wheel-drive cars Transaxle Used in front-wheel-drive cars

4 Purpose of a Transmission
Provide a means of changing torque to fit engine operating requirements Low gear Crankshaft turns three times to one turn of transmission output shaft Small gear drives a larger gear Gears provide leverage

5 Using Gears to Increase Torque and Gear Ratio
Driving gear smaller than driven gear Output speed decreases Output torque increases Gear radius Distance from center of a gear to its outside edge Gear ratio Number of teeth on driven gear divided by number of teeth on driving gear

6 Transmission Gear Ranges and Overdrive
Transmissions in cars and light trucks Three-six forward gear ranges Overdrive Opposite of gear reduction Output shaft turns faster than input shaft Ratio a step beyond 1:1 ratio of high gear Planetary gears Automatic transmission with lock-up torque converter

7 Final Drive Ratio and Gear Types and Operation
Ratio between transmission output shaft and differential ring gear Gear tooth shape Allows teeth to roll into and out of mesh with minimum friction Contact pattern: where teeth of two gears meet Pitch diameter: diameter of meshed gear Manual transmission uses two types of gear Spur and helical gear

8 Spur Gears Simple gears with straight-cut teeth Backlash
One tooth carrying the load at time No end thrust Transmission will not attempt to pop out of gear Backlash Clearance between meshing gear teeth Clicking sound results as one gear rolls out of contact and new one rolls in As backlash noise gains speed, it turns into gear whine

9 Helical Gears and Idler Gears
Helical gears replaced spur gears Quieter Continuous flow of power across gear teeth Minimum backlash Greater gear strength More area of tooth contact Cause end thrust under load Idler gears Used between two other gears Changes output rotation direction

10 Transmission Parts Power flows from clutch disc to input shaft
Each forward gear has a synchronizer Keeps two meshing gears from clashing Shift linkage acts on shift forks within transmission to select gear range Power flows from input shaft to countergear Then to mainshaft or output shaft Parts are housed in transmission case Has drain and fill plugs for adding and draining oil

11 Transmission Lubrication and Transmission Bearings
Transmission parts Separated by oil at all times Splash lubrication Oil moved throughout case by rotating gears Bearings support ends of almost all rotating parts Allow parts to rotate with very little friction Reverse idler shafts and gears Supported by bushings

12 Transmission Gears and Shafts
Countergear Single part made of a series of gears that mesh with various gears on mainshaft Mainshaft Includes all transmission gears and synchronizers Manual transmission Forward gears in constant mesh Reverse idler gear is only gear that moves into mesh with another gear

13 Synchronizer Assembly
Helps two gears spinning at different speeds mesh without clashing Blocking ring synchronizers Shift collar fits around hub outside Gears are in constant mesh Rotate freely on bearing areas Splines on outside of hub become meshed with gear teeth Synchro assembly Locks input shaft gear to output shaft gear


15 Gear Shift Mechanisms and Shift Patterns
Major components: Shift forks: fit into grooves cut in outside of synchro collar Shift linkage: internal shift rail or external rod Detent mechanism: holds transmission in gear Spring tension: holds detent balls into detent notches in shift rail Interlock mechanism: prevents selection of two gears at once Shift patterns: various patterns for different transmissions

16 Transmission Power Flow
Modern transmissions are constant mesh Synchro collar: only thing that moves All manual transmissions operate in a similar fashion Whether there are three speeds or six speeds Five-speed transmissions: most common today Most have direct power in fourth gear Fifth gear provides an overdrive

17 Four-Speed Transmission Power Flow
Four-speed transmission without overdrive Neutral: synchro sleeves centered and do no mesh with clutch teeth of any gear High gear: power runs straight through the transmission from input to output shaft Third gear: power enters through input shaft Second gear: rear synchro sleeve engages engage the second-gear clutch teeth First-gear: rear synchro sleeve is moved toward rear to engage first-gear clutch teeth Reverse: synchro sleeves are in neutral position

18 Five-Speed Transmission
Gear flow in five-speed Same as in first four speeds Extra gears in extension housing Fifth gear: synchro sleeves in transmission case in neutral position Power flow through end of countergear to gear at the end of countergear Some have both reverse and fifth gear in extension housing or rear section of case

19 Speedometer Drive Some cars use electric speedometers
Receive signal from vehicle speed sensor (VSS) Vehicles with VSS If the tire diameter is changed: computer can often be programmed with new tire information Speedometer will be accurate Speed inputs to the computer will be meaningful

20 Switches and Sensors Computer technology
Provided several electronic features to transmissions VSS on late-model transmissions Shift blocking solenoids Reverse lockout Gear range selector switch Sensors are not prone to wear like a switch that has electrical contacts

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