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How Does it Work /
Manual
Transmission
How a Manual Transmission Works
A standard transmission or manual transmission is the traditional type of transmission
used in automobiles. The manual or standard transmission consists of a series of
heliacal gears, syncros, roller bearings, counter shafts and gear selectors. The
main clutch assembly is used to engage and disengage the engine from the transmission.
Heliacal cut gears are used to select the ratio desired the sector fork move gears
from one to another by using the gearshift knob. Syncros are used to slow the gear
to a stop before it is engaged to avoid gear grinding, the counter shaft hold the
gears in place and against the main input and output shaft. A stick shift transmission
has no torque converter so there is no need for a transmission cooler. A stick shift
transmission needs a simple fluid change for proper service. (there is no transmission
filter in a stick shift transmission).
Transmission Shifter
Most manual transmissions have one reverse gear and four to six forward gears.
Some cars also have eight forward gears while thirteen to twenty-four gears are
present in semi trucks. To differentiate among the available standard transmissions,
they are addressed by the number of forward gears. For example, if the standard
transmission has five gears, it will be referred to as 5-speed standard transmission
or 5-speed standard.
Typical Standard Transmission Configuration
Inside the transmission shafts contain all forward and reverse gears. Most transmissions
contain three shafts: input shaft, output shaft and counter or lay shaft. Other
than standard transmission, there are other transmissions like continuously variable
transmission,
automatic transmission and semi-automatic transmission. In the manual transmission,
a pair of gears inside the transmission selects the gear ratios. Whereas, in an
automatic transmission, combination of
brake bands and
clutch packs control the
planetary gear which selects
the gear ratio. If there is a provision to select a gear ratio manually in automatic
transmissions, the system is called a semi-automatic transmission. The driver can
select from any of the gears at any point of time. In some automobiles like racing
cars and motorcycles that have standard transmissions, the driver can select the
preceding or the following gear ratio with no clutch operation needed. This type
of standard transmission is known as sequential transmission. In this transmission
the clutch is still used for initial take off.
Clutch and Flywheel Assembly
The main clutch plays the role of a coupling device which separates the transmission
and the engine. If the clutch is absent and the car comes to a stop the engine will
stall. In automobiles, the clutch can be operated with the help of a pedal
located on the floor of the vehicle. In an automatic transmission instead of a clutch, a torque converter is used to separate
the transmission and engine.
Typical Stick Shift Patterns
A desired gear can be selected by a lever which is usually located on the floor
in between the driver and passenger seat. This selector lever is called the gear
lever or gear selector or gear shift or shifter. This gear stick can be made to
move in right, left, forward and backward direction. When the gear is placed on
the N position or neutral position, no gear will be selected. To move the car in
the backward direction, the R gear or reverse gear should be selected.
Standard transmissions are more efficient and less expensive to produce than automatic transmissions. A Standard transmission is about 15% more efficient
compared to an automatic transmission. Standard transmissions are generally stronger
than
automatic transmissions
and off road vehicles take advantage of a direct gear selection
so they can withstand rough conditions. Less active cooling is also required in manual
transmission system because less power is wasted.
Popular Problem Checks
Car will not go into gear:
- clutch disc is broken completely
- internal transmission damage
- failed clutch master cylinder
- seized clutch slave cylinder
- broken clutch fork pivot
- broken clutch cable
Car goes into gear but it fades out or is slipping
- clutch is worn out and needs replacement
- clutch is oil soaked from a external engine oil leak
Car makes grinding noise while operating or shifting gears
- one of the roller or thrust bearings has failed
- the gear syncro is worn out not forcing the gear stop before it is engaged
causing a grinding gear.
- a counter or main shaft bearing has failed causing misalignment of the gears
troubleshooting Noise and Problems
- If the vehicle is running and a whirring sound is heard, then it goes away
when the clutch is depressed, the transmission input bearing has failed.
- If the transmission is quiet in neutral but when you depress the clutch
a squealing noise is observed, a clutch throw out bearing has failed.
Tips: Never let little noises go unattended; a small noise can cause
a large noise and transmission operation failure. Never overload a vehicle or
tow beyond the capacity this can cause premature transmission failure.
How Does it Work
/ Manual
Transmission
Check Manufacturer Specific Manual
Transmission Question and Answers
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