Note: Descriptions are shown in the official language in which they were submitted.
~5~ 7
Background of the Invention
(1) ~ield of the Invention
The present invention relates to a traveling drive
transmission for a vehicle such as a tractor, and more
particularly to a tra~eling drive transmission adapted to
transmit power from an. engin.e output shaft to a traveling
drive shaft through two alternative lines,
23 Description of the Prior Art
Known traveling drive transmissions for vehicles such
as tractors used in agriculture, civil engineering and
construction, have means to switch between a high speed
range and a low speed range on an input side of a first
speed changing mechanism or main speed changing mechanism9
and in.some cases planetary gearing systems are employed
to eff9ct such switching, The prior art constructiorls QS
such are complicated and unsuitable for incorporating into
a tractor transmission havlng tightly packed gear trains,
Summary of the Invention
Having regard to the above state of the art~ the primary
object of the present i~vention is to provide a traveling
drive transmission of simple constructio~ allowing speed
changing between a high speed range and a low speed range
to be carried out by a ons touch operation, The transmission
accordiDg to thi~ invention is also adapted to perform an
sngine braking function and to enable the ~ngine to be
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8~
started by traction.
To achieve this object, a traveling drive transmission
for a vehicle according to this invention comprises a first
transmission line provided by an engine output shaft
directly connected to a traveling drive shaft operatively
connected to a travel speed changing mechanism, a second
transmission line provided by the engine output shaft
operatively connected to the traveling drive shaft through
a reduction gearing mechanism, the second transmission line
providing a slower speed than the first transmission line,
and clutch means for selecting betweeD the first transmission
line and the second transmission line to transmit power
Bv operating the clutch means a high speed range or
a low speed range is selected forwardly of the travel speed
changing mechanism to enable the tractor to travel at speecls
suited to specific operations. ~lis selecting operation is
carried out more simply than changing of the meshing
relations of gears according to the prior art. In addition,
this 3imple clutch operation is effective to prevent the
engine from stopping at the time of an increased load
falling on the traveling drive shaft, The speed range
switching mechanlsm according to thi3 invention has a
qimpler construction than prior art mechanisms utilizing
planetary ~earing,
~nother object of the present in~ention is to provide
a traveling drive transmission capable of smooth acceleration
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5~7
and deceleration by the above noted speed range switching
operation without involving a temporary drop in the
traveling speed which is a disadvantage of the exlsting
gear mesh changing systems
To this end the present invention provides the clutch
means iocluding a hydraulic clutch mechanism mounted on
the first transmission line and a on2 way clutch mounted
on the second transmission line,
This arrangement has the following advantage, ~en a
load on the traveling drive sha~t increases, the hydraulic
clutch is operated. Then the traveling drive shaft rot~tes
at a lower rate than an output rate of the reduction gearinfr
mechanism, which autoMatically results in a high torque
rotation being smoothly transmitted to the traveling drive
shaft through the one way clutch of the second transmission
line, Thereby the load on the engine is reduced to avoid
its stopping and normal speed changing op~ration may be
carried out,
A further object of the present invention is to enable
th0 engine to be started by traction when an engine starting
system is out of order. To achieve this obJect, the present
invention provides a further one way clutch mounted between
the engine output shaft and the traveling drive shaft to
provide a third transmission line adapted to transmit power
only from the traveling drive shaft to the engine output
shaft.
5r7
Other objects and advantages of the invention will be
apparent from the following description,
Brief Description of the Drawings
.~ig. 1 is a graphic view of a tractor transmission
according to the present invention,
~ ig, 2 is a view in vertical section of a principal
portion of the transmission,
Fig 3 i3 an enlarged view of a part of the principal
portion,
Figo 4 is a view in vertical section of a transmission
according to another embodiment of the invention,
Fig, 5 i5 a view taken on line A-A of Fig. 49 and
Fig, 6 i~ a view taken on lirle B-~ o~ Fig. 5
Description of the Preferred Embodiments
Re~erring to Fig, l graphically showing a whole
transmission of an agricultural tractor~ number 1 denotes
an engine and number 2 denotes a tractor bodyO A first
case 3 and a second cas~ 4 are detachably interconnected
throùgh an intermediate case 5. ~umber 6 denotes a travelin~
system clutch adapted to coDnect and disconnect torque drive
from the engine 1 to ar. engine output shaft 7. Ihis clutch
6 is contained in a front ¢a~e 8 disposed ~orwardly of the
first case 3
The engine output shaft 7 ha~ a hollow cons-truction
5~7
and is supported at a bearing 9 of the first case 3, l~
traveling drive shaft 10 in coæ~ial alignment with the e~,~ine
output shaft 7 is supported at bearings 11 of the first case
3. The traveling drive shaft 10 also has a hollow construction.
The engine output sha.ft 7 and the traveling drive shaft
10 are operatively connected to each other through a hydr~ulic
clutch mechanism 12 and a reduction gearing mechanism 13,
The clutch mechanism 12 and the gearing mechanism 13 are
contained in the first case 3,
A first travel speed changing mechanism 14 is mounted
rearwardly of the hydraulic clutch mechanism 12 in the first
case 3. This speed ch~nging mechanism 14 shown iD Fig. 1
is the constant mesh type adapted to provide four speeds.
The speed changing mechanism 14 comprises a group of gears
15 mounted on the traveling drive shaft 10 and a group of
gears 17 mounted on a speed change shaft 16 extending below
and parallel to the traveling drive shaft 10.
~ second travel speed changing mechanism 18 is contained
between a rear portio~ of the first case 3 and the intermediate
case 5, The second travel speed changing mechanism 18 mainly
comprises a hollow speed change shaft 19 extending coaxially
with the traveling driv~ qhaft 10~ an auxiliary speed change
shaft 20 extending below and parallel to the ~peed change
shaft 19 and coaxially with the speed change shaft 16~ and
groups of speed change gaars 21 and 22 mounted on the shafts
19 and 20, The second travel speed changing mechanism 1
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~$i35~
is shown to further cornprise a backing means 23 and a
creeping speed means 24 to provide three forward speeds
and one backward speed, ~lore particularly9 the second travel
speed ch.nging mecllanism 18 provides a first fo~ard speed
when a shifter 25 is directly connected to the speed chan~re
shaft 16, a second forward speed when a shifter 26 is shifte~
rightward in the drawing to effect speed changing by means of
the gears 21 and 227 a third forward speed when the shiftcr
25 is shifted rightward to transmit power by ~ay of the
creeping speed means 25, and a backward speed when the shifter
26 is shifted leftward to tr~Dsmit power by way of the baclcin,~
means 230
A traveling transmission shaft 27 is operatively
connected to the auxiliary speed change shaft 20 which is
an output shaft of the second speed changing mechanism 18.
Although in the drawi~g these shafts 20 and 27 are connectecl
to each other by a coupling, they may be ~ormed to be one
continuous shaft,
The traveling transmission shaft 27 is operatively
connected to a di~ferential mechanism 28 contained in the
second case 4~ ~ right and left pair of differential OUtpllt
shafts drives rear wheels 30 through a fiDal reduction
mechanism 2~,
Furthermore, the transmission of Fig, 1 is provided
with a front wheel drivs or mid pow~r tc~eoff drive mechanism
31, This mechanism 31 includes a transmission line 33
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i85~
extending parallel to the bottom of the casing and havin~
2 clutch mechanism 3" and operatively connected to the
traveling transmission shaft 27, The power takeoff drive
mechanism 31 is operatively connected also to a power t.~eoff
mechanism 34 provided at an underbelly of the first case 3
below the first speed changing mechanism 34,
Apart from the traveling system described so far, there
is provided a power takeoff drive shaft 35 directly connected
to the engine 1 and extending through the interiors of the
engine output shaft 7, the tra~eling drive shaft 10, and the
speed chaDge shaft 19, A power talceoff clutch mechanism 36
is provided at the rear end of the power takeoff drive shaft .,
35, .By operating this clutch mechanism 36, the power t~{eoff
drive shaft 35 drives a rear power ta~eo.ff shaft through a
16 power t~ceoff speed changing mechanism (not shown) disposed
in a rear portion of the second case 4. This power ta~;eoff
line includes a shift gear 37, When the shift gear 37 is
shifted leftward in the drawing, live power talceoff is
provided through the clutch mechanism 36, 1rhen the shift
gear 37 is shifted rightward~ gro~ld power takeoff is provided
through a gear mounted on the traveling transmission shaft 27,
In the above described transmission the present invention
provides an improvement in transmission at an input side of
the first speed changing mechanism 14, This improvement
is now described in detail with reference to Figs, 2 and 30
The hydraulic clutch mechanism 'l2 comprises a bowl
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shaped clutch body 40 securely fitted together witn a gear
38 on the output shaft 7 by a key 39, a piston 42 fitted in
the clutch body 40 a~iQlly slidably against the force of a
resilient member 41 in form of a disc spring, a plurality
of clutch cliscs consisting of driving friction discs 43 all~]
driven frietion discs 44, and a bowl shaped driven clutcll
hub 45, The elutch hub 45 is in spline engagement with the
forward end of the traveling drive shaft 10, ~le forwarcl
half of the elutch hub 45 concentrieally surrounds the rear
end periphery of the output shaft 7,
The elutch hub 45 is formed with a spline 45~ on its
outer pheriphery to engage the driven frietion dises 44.
An annular dise stopper 46 is mounted by means of a stopper
ring 47 opposite an opening end of' the eluteh body 40.
Retainer mean.s 49 is removably attaehed to the dise stopper
46 by bolts 48, The retainer meaDs 49 is adapted to en~age
at a radially inward eclge thereof with an end of the spline
45~ of the hub 45 in the axial direetion,
The bearing 9 is substantially ~itted in an annular
support 50, The support 50 is fitted against a ~ront opening
of the first ease 3 to seal off lubrieating oil and is
remo~ably attaehed to a wall 53 by bolts 52, l`he support
50 and the wall 53 together render an engine eluteh ehamber
54 oil-free,
A traveling dri~e shaft housing 55 is removably attL~cllecl
to support 50, and a eluteh release hub 58 ~lidably by means
of a. clut~h forlc 57 is Mounted on a tubular portioD of
the casing 55, l~hen the hub 5S slides leftward in tlle
drawing and pushes a clutch lever 599 it disconnects a clutch
plate 61 of the engine clutch 6 from a fl~heel 60.
The clutch plate 61 is splined to the output shaft 7
through a hub 62. i~pplication of hydraulic pressure to the
piston 42 is turned on and off by operating valYe means not
sho~ hydraulis circuit therefor comprises ~n oil passage
63 defined in. the support 50~ an oil passage 64 defined in
the drive shaft casing 55 and communicating with the passage
63, an oil passage 65 defined in the output shaft 7 and
communicating with the passage 64, and an oil passage 66
defined in. the clutch body 40 and communicating with passage
65. i~ cooler passage 67 may be provided in communication
with the oil passage 65 to cool the clutch discs and the like,
The reduction gearing mechan.ism 13 comprises a transmission
~haft 69 supported below and para.llel to the output shaft 7
by a pair of forward and rearward bearings 68 9 a gear 70
mounted on the shaft 69 in mesh with the gear 38 on the
output shaft 79 and a gear 71 mounted on a rearward end o.f
the shaft 69 in mesh with a gear 7Z on the travellng drive
shaft 10. The reduction. gearing mechanism 13 provides a
~econd transmission line B operable when the clutch 12 is
disconDected~ as distinct from a first traDsmission line
effecting direct driving throu~h the ~lutch discs and the
li~e by sliding of the piston 42 to connect the clutcll 12.
-- 10 --
The second transmission line B provides, for example, a
22 per cent reduc-tion of the rate provided by the first
transmission line A.
The second transmission line B further includes a one
way clutch 79 adapted to transmit power only from the
reduction gearing mechanism 13 to the traveling drive shaft
10. This clutch 73 is, for example, the sprag type and is
mounted in the following manner.
The gear 72 is defined peripherally of an annular base
74. The base 74 is relatively rotatably supported through
axially spaced bearings 76 by a hub 75 splined to the forward
end of the traveling drive shaft 10. The clutch 73 is fitted
between the bearings 76 and between the base 74 and the hub
75. A thrust stopper ring 77 is interposed between a forward
end of the hub 75 and the driven clutch hub 45.
A ring plate 78 is mounted in the driven clutch hub 45
between opposing faces of the output shaft 7 and the traveling
drive shaft 10, the ring plate 78 being adapted to engage
the hub 45 and the end surfaces of the two shafts 7 and 10.
A one way~clutch 79 is mounted between an inner surface of
the hub 45 and an outer surface of the output shaft 7 forwardly
of the plate 78. This clutch 79 is, for example, the sprag
type and provides a third transmission line C to transmit
power only from the traveling drive shaft 10 to the output
shaft 7, which is used in effecting engine braking and
traction starting of the engine 1.
~5~35 7
The bearings 68 for the reduction gearing mechanism 13
are held in position by a bearing retainer 80 removably
attached to the support 50,
Thus, the hydraulic clutch mechanism 12 mounted on the
output shaft 7 and the reduction gearing mechanisin 13 are
assembled as one pack onto the support 50, whereby the two
mechanisms 12 and 13 are mounted or drawn out simultaneollsly.
ID this mounting or drawing out operation, the retainer means
49 functions to prevent the clutch hub 45 ~rom dropping of~0
The clutch mechanism 12 and the gearing mechanism 13
are immersed in oil. The one way clutch 73 is cooled by
means of an oil passage 81 defined in the base 74 and the
one way clutch 79 is cooled by mea~s of the oil passage 67.
The order in which the foregoiDg construction is assembled
will be described next and th0n follows a description of its
operation,
The first speed changing mechanism 14, the second speed
changing mechanism 31 and the like are assembled~ and the
power takeoff drive shaft 35 is inserted therein, The hub 75,
the clutch 73 and the base 74 are attached (from front) to the
fo~ard end of the traveling drive ~haft 10 in advance,
Next~ the drive shaft casing 55~ the hydraulic clutch mecl1c~nism
12 and the like are attached to the support 50, and also the
gearing mechanis~n 13 is attached thereto through the bearings
Z5 68, In this state the output shaft 7 is passed along the
po~/er takeoff drive shaft 35 in a skewering manner, ~le
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hydraulic clutch hub l~5 is splined to the travcling drive
shaft 10 and the support 50 is fixed to the wall 53 by the
bolts 52. The assembly is completed by mounting the engine
clutch 6. The disassernbly is carried out in the reverse
order,
During the assembly and disassembly the retainer means
49 prevents the hub 45 from falling off by engaging its spline,
Turning now to how this construction operates, torque
from the engine 1 to the output shaft 7 is connected or
broken by operating the clutch 6.
~ en.hydraulic pressure is applied to the piston 42
of the hydraulic clutch mechanism 12~ the output shaft 7 and
the traYeling drive shaft 10 are directly connected by the
clutch 12 whereby establishing the first transmission line .
to transmit the engin.e power ~straight to the traveling drive
shaft 10. ~en the hydraulic clutch mechanism 12 is
disconDected~ power is transmitted from the output shaft 7
through the reduction gearing mechan.ism 13 to the traveling`
drive shaPt 10, namely by way of the second transmission
line B, at a reduced rateO In this latter instance the
tra~eling drive shaft 10 is driven through the one way clutch
75 in the same direction as in the case of directiQn connection
to the output shaft 7, When an. engine starting system fails~
the tractor may be towed to cause the traveling drive shaft
10 to rotate and transmit power through the clutch 79, tlle
output shaft 7 to the engine 1 thereby to start the engine 1.
~ t7
The clutch 79 is operable to effect engine braking also.
The traveling drive transmission for a vehicle according
to another embodimen-t is now described in detail,
Referring to Figs, 4 and 5~ a tractor body 101 comprises
a clutch housing 102 and a transmission case 103. ~umber
104 der~otes a flywheel mounted on a crankshaft of an engine,
traveling system clutch 105 is provided on the flywheel
104 and includes a release lever 106. The clutch 105 is
operatively connected to a clutch pedal not shown through
a release hub 107, a release fork 108 and a fork rod 109,
Number 110 denotes an attaching member whose main body portion
112 is peripheral~y removably fixed by bolts 113 to a support
wall 111 formed on tlle clutch housing 102, The attaching
member's main body portion 112 carries a forwardly projecting
traveling drive shaft casing 114 at an upper portion thereof
and a rearwardly projecting bearing retainer 115 at a lower
portion thereof. The release hub 107 is fitted on the drive
shaft casing 114 to be slidable backward and forward, The
bearing retainer 115 is held rigid by a right and left pair
of supports 115~ Number 117 denotes a power takeoff drive
shaft directly connected to the flywheel 104 and operatively
connected to a power tc~keoff speed char~ging mechanism
through a power takeoff clutch not shown, ~umber 118 denotes
a hollow traveling dri~e shaft loosely fitted on the power
takeo~f drive shaft 117 and rotatably mounted in the drive
shaft casing 114 by means of bearings 11~ and 120. The
5t7
traveling drive shaft 1l~ is in operative connection with
the traveling system clutch 105. Number 121 del70tes a
hollow traveling transmission shaft loosely fitted on the
power talceoff drive shaft 117 rearwardly of the traveling
drive shaft 118 and supported by a partition wall 123
through a bearing 1220 ~umber 1Z4 denotes a travel speed
changing mechanism mounted in the transmission case 103,
Number 125 denotes a reduction shaft mounted below and
parallel to the traveling drive shaft 118 and rotatably
supported at both ends by bearings 126 and 127 fitted in the
main body portion 112 of the attaching member 110 and the
bearing retainer 115 respectively, The reduction sha~t 125
carries adjacent to the forward end thereof a gear 128
rotatable in unison therewith and at the rearward end thereof
a gear 129 integral therewith, The gear 128 is in constant
mesh with a gear 130 freely rotatably mounted on the traveling
drive shaft 118, and the gear 129 .is in constant mesh with
a gear 131 mounted on the foward end of the traveling
transmission shaft 121. The reduction shaft 125 and the
gears 1309 128, 129 and 131 constitute a reduction mechanism
133 whose reducti.on rate is iD the order of 30 per cent.
Number 134 den.otes a high speed range hydraulic clutch adapted
to directly couple the traveling drive shaft 118 to the
traveling transmission ~haft 121. Number 135 denotes a low
speed ran~e clutch adapted to connect the travelin~ drive
shaft 118 and the traveling transmission shaft 121 by way of
- 15 ~
~ St7
the reduction mechanism 133. The two clutches 134 and 13-~
are arranged one behind the othcr axially of the trave1ing
drive shaft 118 and the tr~eling tr~nsmission shaft 1`1
and are assembled into a common driving disc 136, ~ore
particularly9 the hydraulic clutches 134 anc1 135 comprise
the dri~ing disc 136 keyed to the rear end of the travelil]g
drive shaft 1187 annular cylinder chambers 137 and 138
provided forwardly and rea~ardly of the driving disc 13~"
pistons 139 and 140 slidably mounted in the cylinder cha~bers
137 and 138, support plates 141 and 142 fitted in fo~ard
and rearward ends of the driving disc 136, driven members
143 and 144, and a plurality of clutch discs 145 and 146 ~1is-
posed between the pistons 139 and 140 and the support plates
141 and 142 and connected to the driving disc 136 and to
the driven members 143 and 144, respectively. The pistons
139 and 140 are held rigid together in the axial direction
at plural peripheral positions by spacer collars 147 and
bolts 148. Each of the spacer co:Llars 147 is ~xially
slidably fitted in a receiving bore defined on the dri~ing
disc 136 between the cylinder chambers 137 and 138. Of the
two cylinder chambers 137 aDd 138, the chamber 138 associated
with the low speed range clutch 135 includes resilient me~l-s
149 to bias the piston 140 in a direction to compress the
clutch plates 1469 Damely in a direction to engage the cl~ltch
135. The resilient means 149 comprises an annul~r disc
spring. The driven member 143 is splined to the forwar
_ 16 -
5~
end of the traveling tr~ns~nission shaft 121 while -the
driven member 144 i9 integral with *he gear 138 and is
freely rotatably fitted on the traveling drive shaft 11~.
Each of the cylinder chambers 137 and 138 is in communicat:ion
with a control valve not shown via oil passages 150 and 1,1
def.ined in the traveling drive sha~t 118 and the attaching
member 110 respectively, whereby pressure oil is supplie-l
in a controlled manner from a hydraulic pump not shown
directly connected to the engine.
llow the described construction operates is described
next, I`he hydraulic pump operates while the engine is
running When the control valve is set for a high speed
range, the pressure oil from the hydraulic pump is fed to
the cylinder chamber 137, This causes the piston 139 to
compress the clutch discs 145 disposed bet~een the pis-ton
139 and the support plate 141 and to connect the driving
disc 136 to the driven member 143 through the clutch discs
145~ which places the high speed range hydraulic clutch 134
in operation, Therefore, with the traveling clutch 105
connected, engine power is transmitted through the traveling
clutch 105, the traveling drive shaft 118, the high speed
range hydraulic clutch 134, the traveling tra.~smission shaft
121, to the travel speed changing mechanism 124, thereby
enabling the tractor to travel at a desired spee~.
While the tractor runs on the road or engage in normal.
ground working, the high speed range clutch 134 is connecte~l
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S 7
to transmlt power as described above, If an excessive
load occurs for some reason or other reducing the rotationlL
rate of the engine, then the control valve ls set for the
low speed r~nge to switch from the high speed range
hydraulic clutch 134 to the low speed r~nge hydraulic clllt~
135, whereupon the traveling speed is reduced by about 30
per cent by the reduction mech~ism 133 in order to avoic]
stopping o~ the eDgine, In other words, when the control
~alve is set for the low speed range, the pressure oil
enters the cylinder chamber 138 and the piston 140 presses
the clutch discs 146 against the support plate 1ll2 to
connect the driving disc 136 to the driven member 144 ~ia
the clutch discs 146 thereby establishing the operation of
the low range hydraulic clutch 135. l~ccordingly the output
of the traveling drive shaft 118 is transmitted by way of
the driving disc 136, the clutch c~lisc 146~ the driven
member 144, th~ gear 130, the gear 1Z8, the reduction shaft
125~ the gear 129, the gear 131 and to the traveling transnlission
shaft 121. Since the speed is reduced b~tween the gears 130
and 128 and between the gears 129 and 131 by about 30 per
cent, the tractor will slow down thereby preventing the
en~ine from stopping, The control valve is returned to tlle
high ~peed range when the overload on the engine is eliminatecl
and its rotational rate is reeovered. The traveling speed
of the tractor is very easily changed in both ways, namely
for acceleration and for deceleration~ by switching the
- 18 _
control val~e,
In case the engiDe stops running thereby to cut oil
supply from the hydraulic pump, the resilient mec~ns 149
mounted in the cylinder chamber 13~ of the low speed range
hydraulic clutch 135 presses against the piston 1 40 to
compress the cl.utch dlscs 146 between the piston 140 and
the support plate 142 thereby placing the low speed range
hydraulic clutch in operation, Therefore, when the engine
stops during uphill traveling or the likep the low speed
range clutch 135 will immediately operate to effect a
braking action by means of the engine thereby to avoid
accident, Since the resilient means 149 is mounted in the
low speed range hydraulic clutch 1359 the resilient means
149 may have a small resilient force compared with the case
of being mounted in the high speecl range hydraulic clutch
134, ~oreover~ since the two pistons 139 and 140 are rigidly
interconnected in the a~ial direction by the spacer collars
147 and the bolts 148, the resilient means 149 also f~mctions
as returD means for the high speed range hydraulic clutch 134,
~s described above, the low speed range hydraulic
clutch 135 is in operative condition whenever the engine stops,
Therefore1 it is possible to start the engine by towing the
tractor,
l`his in~ention as embodied above provides the high speed
ran~e hydraulic clutch adapted to directly connect the
traveling dri~e shaft to the traveling transmiss:ion shaft,
~ 19 _
and the low s~eed range hydraulic clutch adapted to connect
the two shafts through the reduction mechanism, whereby
switching between the high speed range and the low speed
range is effected by operating the control valve select
the hifrh speed range hydraulic clutch or the low speed ran,~re
hydraulic clutch, and such a switching operation is a very
easy~ one touch operation Thus, even when the e~gine is
subjected to a frequent occurrence of excessively heavy
load, its inadvertent stopping can be avoided by slowing
down the tractor or switching from the high speed range to
the low speed range
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