Automobile Gearbox

1
Automobile Gearbox

• BY
• GAURANG PRAJAPATI

2
The word Transmission

• The word transmission means the mechanism that
  transmits the power from the engine crank shaft
  to the rear wheels.

3
Function of Transmission

• Provide a means to vary torque ration between the
  engine and the road wheels as required.
• Provides a neutral position.
• A means to back the car by reversing the
  direction of rotation of the drive is also
  provided by the transmission.

4
Gear Ratio
The gear ratio, or velocity ratio, between a
pair of gear wheels is in inverse ratio to the
number of teeth on each.
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Gear Ratio
Thus, NB/NA DA/DB nA/nB NB NA (nA/nB)
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Gear Ratio
Where NA rev per min of gear A, nA   number of
teeth on A NB rev per min of gear B, nB  
number of teeth on B DA Diameter of gear ADB
Diameter of gear B
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Types of Gearbox

• Sliding mesh gearbox
• Constant mesh gearbox
• Synchromesh gearbox
• Epicyclic Gearbox

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Sliding mesh type gearbox

• Constant mesh gears.
• Primary shaft (Clutch shaft)
• Spigot bearing.
• Main shaft.
• Lay shaft (counter shaft)

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Sliding mesh type gearbox
Primary shaft

• This shaft transmits the drive from the clutch to
  the gearbox .
• At the end, the shaft is supported by a spigot
  bearing positioned close to the splines on to
  which the clutch driven plate is connected.

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Sliding mesh type gearbox
Primary shaft

• The main load on this shaft is taken by a
  bearing normally a sealed radial ball type,
  positioned close to an input gear called a
  constant mesh pinion.

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Sliding mesh type gearbox
Primary shaft

• The gear is so named because it is always in mesh
  with a larger gear
• Small driving gear is called a pinion and a large
  gear a wheel.

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Sliding mesh type gearbox
Layshaft

• This shaft, which is normally fixed to the
  gearbox casing, supports the various-sized
  driving pinions of the layshaft gear cluster

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Sliding mesh type gearbox
Main Shaft

• This splined output shaft carries spur gearwheels
  that slide along the shaft to engage with the
  appropriate lay shaft gears.
• At the front end, the main shaft is supported
  by a spigot bearing situated in the centre of the
  constant mesh pinion.

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Sliding mesh type gearbox
Main Shaft

• A heavy duty radial ball bearing is fitted at the
  other end to take the force of the gears as the
  attempt to move apart.

15
Sliding mesh type gearbox

• The power comes from the engine to the clutch
  shaft and thence to the clutch gear which is
  always in mesh with a gear on the lay shaft.
• All the gears on the lay shaft are fixed to it
  and as such they are all the time rotating when
  the engine is running and clutch is engaged.

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Sliding mesh type gearbox
Gear position
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Sliding mesh type gearbox
Neutral

• All main shaft gearwheels are positioned so that
  they do not touch the layshaft gears.
• A drive is taken to the layshaft, but the
  mainshaft will not be turned in neutral position

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First gear
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Second
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Third
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Top
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Reverse
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Disadvantage of Sliding mesh Gearbox

• Gear noise due to the type of gear.
• The difficulty of obtaining a smooth, quit and
  quick change of gear without the great skill and
  judgment.

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Selector Mechanism

• A fork is used to slide a gearwheel along the
  main shaft in order to select the appropriate
  gear.
• It is mounted on its own rod and links the
  drivers gear stick to the sliding gearbox.

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Selector Mechanism
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Selector Detent

• It holds the gears and selectors in position and
  so prevent gear engagement or disengagement due
  to vibration.
• The figure shows a typical arrangement suitable
  for a layout having the selector fork locked to
  the rod

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Interlock Mechanism
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Interlock Mechanism

• Prevents two gears engaging simultaneously
• If this occurs the gearbox will lock up and shaft
  rotation will be impossible.

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Power take-off arrangement

• In addition to the mechanism use for driving a
  vehicle along a road, a power supply is often
  required for operating external items of
  auxiliary equipment.
• A light truck having a tipping mechanism is one
  example, but the most varied application of power
  take-off units is associated with specialized
  off-road vehicles

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Power take-off arrangement
31
Constant mesh gearbox

• All the gear are in constant mesh with the
  corresponding gears on the layshaft. The gears on
  the splined main shaft are free
• The dog clutch are provided which are free to
  slide on the main shaft.
• The gears on the lay shaft are fixed.

32
Constant mesh gearbox
33
Constant mesh gearbox

• When the left dog clutch is slid to left by means
  of the selector mechanism, its teeth are engaged
  with those on the clutch gear we get the direct
  gear.

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Constant mesh gearbox

• The same dog clutch when slid to right makes
  contact with the second gear and second gear and
  second gear is obtained.
• Similarly movement of the right dog clutch to the
  left result in low gear and towards right in
  reverse gear.

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Double Declutching with Constant mesh Gearbox

• For the smooth engagement of the dog clutches it
  is necessary that the speed of the clutch shaft,
  layshaft and main shaft gear must be equal.
• Therefore to obtain lower gear, the speed of
  clutch shaft, layshaft and the main shaft gear
  must be increased.
• By Double declutching this can be done.

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Double Declutching with Constant mesh Gearbox

• The clutch is disengaged and the gear is brought
  to neutral.
• Then the clutch is engaged and accelerator pedal
  pressed to increased the speed of the main shaft
  gears.

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Double Declutching with Constant mesh Gearbox

• After this the clutch is again disengaged and the
  gear moved to required lower gear and the clutch
  is again engaged.
• As the clutch is disengaged twice in this
  process, it is called double declutching

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Advantage of Constant mesh Gearbox compared to
Sliding mesh Gearbox

• As the gear remain always in mesh, it is no
  longer necessary to use straight spur gear.
  Instead helical gear is used which are quieter
  running.

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Advantage of Constant mesh Gearbox compared to
Sliding mesh Gearbox

• Wear of dog teeth on engaging and disengaging is
  reduced because here all the teeth of the dog
  clutches are involved compared to only two or
  three teeth in the case of sliding gears.

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Synchromesh Gearbox

• Similar to constant mesh type, because all the
  gears on the main shaft are in constant mesh with
  corresponding gears on the layshaft.
• The gears on the main shaft are free to rotate on
  it and that on the layshaft are fixed to it.

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Synchromesh Gearbox

• Avoids the necessity of double declutching.
• The parts which ultimately are to be engaged are
  first brought into frictional contact which
  equalizes their speed, after which these may be
  engaged smoothly.

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Synchromesh Gearbox
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Synchromesh Gearbox

• A engine shaft.
• Gears B,C,D,E are free on the main shaft and
  always mesh with corresponding gears on lay
  shaft.
• Members F1 and F2 are free to slide on splines on
  the mainshaft.
• G1 and G2 are ring shaped members having internal
  teeth fit onto the external teeth on members F1
  and F2 respectively.

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Synchromesh Gearbox

• K1 and K2 are dog teeth on B and D respectively
  fit onto the teeth of G1 and G2.
• S1 and S2 are the forks.
• T1 and T2 are the ball supported by springs.
• M1,M2,N1,N2,P1,P2,R1,R2 are the frictional
  surfaces.

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Synchromesh Gearbox

• T1 and T2 tend to prevent sliding of members
  G1(G2) on F1(F2).
• When force applied on G1(G2) through forks S1(S2)
  exceeds a certain value, the balls are overcome
  and member G1(G2) slides over F1(F2).
• There are usually six of these balls
  symmetrically paced circumferentially in one
  synchromesh device.

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Engagement of direct gear in Synchromesh Gearbox
Cones M1 and M2 mate to equalize speeds.
Member G1 pushed further to engage with dog k1
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Engagement of direct gear in Synchromesh Gearbox

• For direct gear, member G1 and hence member F1 is
  slid towards left till cones M1 and M2 rub and
  friction makes their speed equal.
• Further pushing the member G1 to left cause it to
  override the balls and get engaged with dogs k1.
• So the drive to the mainshaft is direct from B
  via F1 and the splines.

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Engagement of direct gear in Synchromesh Gearbox

• Similarly for the second gear the members F1 and
  G1 are slid to the right so that finally the
  internal teeth on G1 are engaged with L1.
• Then the drive to mainshaft will be from B via
  U1, U2, C, F1 and splines.
• For first gear, G2 and F2 are moved towards left
• The drive will be from B via U1, U3, D, F2 and
  splines to the main shaft.

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Engagement of direct gear in Synchromesh Gearbox

• For reverse, G2 and F2 are slid towards right.
• In this case the drive will be from B via U1, U4,
  U5, E, F2 and splines to the main shaft.

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Its too simple to Understand
51
Selector Mechanism with gear lever on top of the
transmision
52
Selector Mechanism with gear lever on top of the
transmision

• There are forks mounted on the sleeves on three
  separate selector rods which are supported in the
  gearbox casing.
• Each selector sleeve can slide on its rod.
• There are slots on the selector rods and the
  sleeves are provided with spring loaded balls to
  avoid unwanted engagement of the gears.

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Selector Mechanism with gear lever on top of the
transmision

• These balls resist the movement of the forks
  until some force is applied to the gear lever to
  overcome their resistance.
• Grooves are provided on the gear bosses where the
  selector forks can fit in.
• Transverse motion of the gear lever selects the
  forks which is to be engaged and the longitudinal
  movement then slides the forks and its gear to
  engage the selected gear.

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Selector Mechanism with gear lever on top of the
transmision

• Various gear position are marked on the gear
  lever knob itself.

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Epicyclic Gearbox
PLANET
SUN GEAR
RING GEAR
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Epicyclic Gearbox

• An epicyclic gearbox consists of two, three or
  even four epicyclic or planetary gear sets.
• A simple gear set has a sun gear, about which
  planets turns round.
• These planet gears are carried by a carrier and a
  shaft and are also in mesh with a ring gear.

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How The Gears Move
The white band with blue bars behind the
planets represents the planet carrier. 
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Principle of Algebraic Method
The gear ratio of a pair of mating gear
wheels with respect to the link carrying the axes
of the gears is always the same whether the link
carrying axes is fixed or moving.
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Speed Ratio

• Here gears B and C mating with each other and
  connected by means of arm A.
• So according to principle
• Speed of the gear B w.r.t arm A - TC
• Speed of the gear B w.r.t arm A TB

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Controls in Epicyclic Gearbox

• There are two controls i.e. the brake and the
  clutch.
• The brake is in the form of a band that surrounds
  a drum attached to the gear (in case of sun gear)
  or the outer surface of the gear itself (in case
  of ring gear).
• The clutch used is of multiplate type.

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Controls in Epicyclic Gearbox

• Both the brake and the clutch are applied by the
  fluid pressure.
• These are selected by hydraulic shift valves
  which are usually located at the bottom of the
  gearbox.

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Advantage of Epicyclic Gearbox

• All gear are in constant mesh and to engage any
  desire gear one simply has to apply the
  particular brake or the clutch.
• For this, the drive from the engine need not to
  be disconnected as in case of ordinary gearbox.
• Thus gear changing operation becomes very easy
  with an epicyclic gearbox.

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ZF-Ecomid

• GEARBOX

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Some Technical Data
Model Model 9 S 7 5 9 S 7 5
Input torque max Nm Input torque max Nm 770 900
Ratios Crawler 13.6 9.56
Ratios Forward gear 8.91-1.00 6.47-0.73
Ratios Reverse gear 11.74 8.53
Speedometer Mechanical 1.556 1.556
Speedometer Electronic Z6 Z6
Installation Installation Flange mounted on engine installation potion horizontal to the left or vertical Flange mounted on engine installation potion horizontal to the left or vertical
Shift system Four-speed section Crawler / reverse gear with dog clutch engagement, all other gears synchronized. Crawler / reverse gear with dog clutch engagement, all other gears synchronized.
Shift system Range change group Synchronized. Synchronized.
Shift actuation Four speed section Mechanical with turning shaft control with double H or superimposed H shift pattern Mechanical with turning shaft control with double H or superimposed H shift pattern
Shift actuation Range change group Double H changes are carried out and controlled automatically . Superimposed H changeover using preselector switch on shift lever. Double H changes are carried out and controlled automatically . Superimposed H changeover using preselector switch on shift lever.
Weight (approx. Kg) Weight (approx. Kg) Approx. 125 kg weight without additional equipment Approx. 125 kg weight without additional equipment
Oil volume horizontal/ vertical position. Oil volume horizontal/ vertical position. Approx 10.5 dm3 / 9.5 dm3 Approx 10.5 dm3 / 9.5 dm3
Oil grade Oil grade According to relevant ZF list of lubricants, TE-ML 02 According to relevant ZF list of lubricants, TE-ML 02
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ZF-Ecomid Gearbox

• ZF-Ecomid transmission consist of a 4-speed
  section with crawler and reverse gear .
• The transmission is of counter-shaft type.
• The rear mounted planetary range change group
  double the number of ratios in 4-speed section.

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ZF-Ecomid Gearbox

• Together with crawler, this equips with 9 forward
  gears.
• Gears 1-4 from the low range and gears 5-8 from
  the high in the range-change group

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• 4-speed section
• Synchronized, Reverse gear and crawler with
  constant mesh.
• Mechanical shift operation.
• Double-H shifting or super-imposed H shifting
• Range-Change group
• Synchronized
• Automatic changeover in transition from gate 3/4
  to gate 5/6 and vice versa (pneumatic) with
  double H shift pattern.
• Changeover with preselector switch on shift lever
  with super imposed H shift pattern

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Shift Actuation

• 1. Range Change Group Double H Shift Mechanism
• 2. Range Change Group Superimposed H Shift
  Mechanism

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Selector patent-1
Selector patent-1
Selector patent-2
Selector patent-2
Superimposed H shift pattern
Double H Pattern
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Double H Shift Mechanism

• This shift mechanism divided into 5 adjacent
  gates.
• There is spring loaded neutral position in both
  gates 3/4 and 5/6.

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Double H Shift Mechanism

• Different strengths of spring detent enable the
  driver to navigate effectively through the
  transmission shift pattern.
• The pneumatic selection feature operates
  automatically when changing from gate 3/4 to 5/6
  or back again.

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Superimposed H Shift Mechanism

• The shift mechanism divided into 3 adjacent
  gates.
• There is spring loaded Neutral position in gates
  3/4 and 7/8.

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Superimposed H Shift Mechanism

• The pneumatic selection feature operated via the
  preselection switch on the shift lever when
  changing from gate 3/4 to gate 5/6 or back again.

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Shifting of Transmission

• ZF-Ecomid transmissions are synchro-mesh
  transmission.
• A synchromesh transmission is one which enables
  all gears to rotate in the same direction at
  synchronous speeds.
• This system makes process quicker and more
  reliable.

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Shifting of Transmission

• There isnt any problem of double declutching
  during up shifts.
• No intermediate throttle application and no
  double declutching when shifting down, even when
  driving downhill and in difficult situations.

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Transmission Shift Pattern

1. Double H Shift Pattern.
2. Superimposed H Shift pattern.

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Double H Shift Pattern

• The double H shift pattern has what is known as
  neutral position in gates 3/4 (low range ) and
  5/6 (High Range).

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Double H Shift Pattern

• To select gates 1/2 or 7/8, move the selector
  level against spring force in the relevant
  direction and hold against this force when
  selecting.
• The selector lever jumps back to the neutral when
  released from mid-position of the gate.

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Double H Shift Pattern

• Gate 3/4 and 5/6 are separated by a more powerful
  spring detent.
• During this gate change, an automatic changeover
  is performed in the range change group.
• The gate for reverse gear is protected by a pawl
  stop and requires more force to be applied.

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Double H Shift Pattern

• The different level of spring force provided good
  orientation within the shift pattern , i.e. the
  gates can be located with reliable certainty.

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Superimposed H Shift Pattern

• The superimposed H shift pattern has a spring
  loaded return to neutral (idling) in the 3/4 (low
  range change group) and 7/8 (high range change
  group) gates.

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Superimposed H Shift Pattern

• To select gates 1/2 or 5/6, move the selector
  lever jumps against spring force in the relevant
  direction and hold against this spring force when
  selecting.
• The selector level jumps back to the neutral when
  released from the mid-position of the gate.

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Superimposed H Shift Pattern

• The reverse gear is secured by means of a bolt
  detent and additional force has to be exerted to
  select it.

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Gear Selection

• Move the selector rapidly without too much
  force. This is important when the transmission
  oil is still cold.
• When selecting gear, hold the selector lever
  against the pressure point until the
  synchronizing process is complete and the gear
  has engaged properly.

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Gear Selection

• For Double H Change out of the ¾ gate into 5/6
  gate or vice versa by briefly striking the shift
  lever with your palm of your hand and swiftly
  moving the shift lever into the gear required
  without exerting too much force.

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Gear Selection
Down Shifting
Up Shifting
Gate change
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Gear Selection

• For superimposed H if someone wants to shift from
  4th gear into the 5th gear in the basic
  transmission then he
• must Preselect high ratio (high range group) on
  selector switch
• Disengage the clutch pedal
• Shift into neutral at which point the range
  change group starts to change over.
• Select gate ½.
• Shift the basic transmission into 1st gear the
  range change group will by now have shifted into
  high ratio
• Engage the clutch
• Leave preselector switch in the selected range
  group

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Bleeding the Transmission
Why???

• The transmission oil heats up during travel.
• This results in formation of excess pressure
  which is continuously removed via a bleed valve

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• PART
• IDENTIFICATION
• ZF-GEARBOX

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Slave cylinder
Oil line
Air line
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Z-bracket
Gear shifting bracket
Bush
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Neutral Gear sensor
Reverse gear sensor
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Speedometer Sensor
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Crawler gear sensor
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Gear Shifting Bracket
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Oil Drain Plug
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• THANK
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