#### Transcript GFG - Worldtruck's Blog | The Best Technical Guider

```Automobile
Gearbox
• BY:
GAURANG PRAJAPATI
1
The word “Transmission”
• The word transmission means the
mechanism that transmits the
power from the engine crank shaft
to the rear wheels.
2
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.
3
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.
4
Gear Ratio
Thus,
NB/NA = DA/DB= nA/nB
NB = NA (nA/nB)
5
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 A
DB = Diameter of gear B
6
Types of Gearbox
• Sliding mesh gearbox
• Constant mesh gearbox
• Synchromesh gearbox
• Epicyclic Gearbox
7
Sliding mesh type gearbox
1.Constant mesh
gears.
2.Primary shaft
(Clutch shaft)
3.Spigot bearing.
4.Main shaft.
5.Lay shaft
(counter shaft)
8
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.
9
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.
10
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.
11
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
12
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.
13
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.
14
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.
15
Sliding mesh type gearbox
Gear position
16
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
17
First gear
18
Second
19
Third
20
Top
21
Reverse
22
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.
23
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 driver’s gear stick to the
sliding gearbox.
24
Selector Mechanism
25
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
26
Interlock Mechanism
27
Interlock Mechanism
• Prevents two gears engaging
simultaneously
• If this occurs the gearbox will lock
up and shaft rotation will be
impossible.
28
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 takeoff units is associated with specialized
29
Power take-off arrangement
30
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.
31
Constant mesh gearbox
32
Constant mesh gearbox
• When the left dog clutch is slid to
left by means of the selector
mechanism, it’s teeth are engaged
with those on the clutch gear we
get the direct gear.
33
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.
34
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.
35
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.
36
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
37
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.
38
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.
39
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.
40
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.
41
Synchromesh Gearbox
42
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.
43
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.
44
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.
45
Engagement of direct gear in
Synchromesh Gearbox
Cones M1 and M2 mate to
equalize speeds.
46
Member G1 pushed further
to engage with dog k1
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.
47
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.
48
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.
49
It’s too simple to Understand
50
Selector Mechanism with gear
lever on top of the transmision
51
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.
52
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.
53
Selector Mechanism with gear
lever on top of the transmision
• Various gear position
are marked on the
gear lever knob itself.
54
Epicyclic Gearbox
PLANET
SUN GEAR
RING GEAR
55
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.
56
How The Gears Move
The white band with
blue bars behind the
planets represents the
planet carrier.
57
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.”
58
Speed Ratio
C
B
• Here gears B and C mating with
each other and connected by
means of arm A.
• So according to principle
A
Speed of the gear B w.r.t arm A = - TC
Speed of the gear B w.r.t arm A
TB
59
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.
60
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.
61
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.
62
ZF-Ecomid
GEARBOX
63
Some Technical Data
Model
9S75
Input torque max Nm
770
900
13.6
9.56
Forward gear
8.91-1.00
6.47-0.73
Reverse gear
11.74
8.53
Crawler
Ratios
Speedometer
Mechanical
1.556
Electronic
Installation
Shift system
Shift
actuation
Z=6
Flange mounted on engine; installation potion horizontal to the left or
vertical
Four-speed section
Crawler / reverse gear with dog clutch engagement, all other gears
synchronized.
Range change group
Synchronized.
Four speed section
Mechanical with turning shaft control with double H or superimposed
H shift pattern
Range change group
Double H: changes are carried out and controlled automatically .
Superimposed H: changeover using preselector switch on shift lever.
Weight (approx. Kg)
Approx. 125 kg weight without additional equipment
Oil volume horizontal/ vertical
position.
Approx 10.5 dm3 / 9.5 dm3
According to relevant ZF list of lubricants, TE-ML 02
64
ZF-Ecomid Gearbox
• ZF-Ecomid transmission consist
of a 4-speed section with crawler
and reverse gear .
• The transmission is of countershaft type.
• The rear mounted planetary range
change group double the number
of ratios in 4-speed section.
65
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
66
•
•
•
•
•
•
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
67
Shift Actuation
1. Range Change Group Double H Shift
Mechanism
2. Range Change Group Superimposed H Shift
Mechanism
68
Selector patent-1
Selector patent-2
Superimposed H shift pattern
Selector patent-1
69
Selector patent-2
Double H Pattern
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.
70
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.
71
Superimposed H Shift
Mechanism
• The shift mechanism
divided into 3
• There is spring loaded
Neutral position in
gates 3/4 and 7/8.
72
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.
73
Shifting of Transmission
• ZF-Ecomid transmissions are synchromesh 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.
74
Shifting of Transmission
• There isn’t 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.
75
Transmission Shift Pattern
1. Double H Shift Pattern.
2. Superimposed H Shift pattern.
76
Double H Shift Pattern
7
• The double H
shift pattern has
what is known as
neutral position
in gates 3/4 (low
range ) and 5/6
(High Range).
5
3
1
R
N
8
N
6
4
2
C
77
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.
78
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.
79
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.
80
Superimposed H Shift Pattern
7
• The superimposed
H shift pattern has
(idling) in the 3/4
(low range change
group) and 7/8
(high range change
group) gates.
5
N
3
1
R
8
N
6
4
2
81
C
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 midposition of the gate.
82
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.
83
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.
84
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.
85
Gear Selection
Down Shifting
Gate
86 change
Up Shifting
Gear Selection
• For superimposed H if someone wants to shift from
4th gear into the 5th gear in the basic transmission
then he
1. must Preselect high ratio (high range group) on selector
switch
2. Disengage the clutch pedal
3. Shift into neutral – at which point the range change group
starts to change over.
4. Select gate ½.
5. Shift the basic transmission into 1st gear – the range change
group will by now have shifted into high ratio
6. Engage the clutch
7. Leave preselector switch in the selected range group
87
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
88
PART
IDENTIFICATION
ZF-GEARBOX
89
Slave
cylinder
Oil line
Air line
90
Z-bracket
Gear
shifting
bracket
Bush
91
Neutral
Gear
sensor
Reverse
gear
sensor
92
Speedometer
Sensor
93
Crawler
gear sensor
94
Gear
Shifting
Bracket
95
Oil Drain
Plug
96
THANK
YOU
97
```