5
4263110-Rev B 5-1
Chapter 5
Hydrostatic Power Train
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
Test Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
Repair Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
Hydraulic Hose, Tube, and Fitting General Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
O-Ring Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
Hydraulic Hose Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
Hydraulic Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
Portable In-Line Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
Digital Hydraulic Tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6
Hydraulic Flow Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6
Digital Pressure Gauge Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Hydraulic Hose Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Flow Lock Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Hydraulic Test Fitting Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7
Blocking Disk Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Component Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8
Theory of Operation and Sub-Circuit Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
Traction Circuit—Neutral Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . 5-9
Traction Circuit—Neutral Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10
Traction Circuit—Forward 4WD Schematic and Theory of Operation . . . . . . . . . . . . . . . . . 5-13
Traction Circuit—Forward 4WD Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14
Traction Circuit—Reverse 4WD Schematic and Theory of Operation . . . . . . . . . . . . . . . . 5-17
Traction Circuit—Reverse 4WD Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18
Traction Circuit—Forward 2WD Schematic and Theory of Operation . . . . . . . . . . . . . . . . . 5-21
Traction Circuit—Forward 2WD Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22
Traction Circuit—Reverse 2WD Schematic and Theory of Operation . . . . . . . . . . . . . . . . 5-25
Traction Circuit—Reverse 2WD Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28
Tests and Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30
Neutral Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30
Traction Pedal Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-32
Weight Transfer Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-33
Field Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-34
Preliminary Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-34
Traction System Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-34
Wheel Motor Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-35
5-2 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Instrument Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-36
Instrument Test Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-36
Charge Pressure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-37
Traction System Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-38
Traction Pump and Front Wheel Motors Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-41
4WD Valve and Rear Wheel Motors Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-46
Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-51
Drive Shaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-51
Traction Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-53
4WD Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-59
Rear Wheel Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-61
Front Wheel Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-65
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-3
5
Specifications
Test Specifications
Specification
Traction Pump Flow gpm (lpm) 32.8 (124) at 2700 rpm
Forward System Relief Pressure
psi (bar) 4387 ± 10% (302 ± 10%) at 2700 rpm
Reverse System Relief Pressure
psi (bar) 4387 ± 10% (302 ± 10%) at 2700 rpm
Charge Pressure
psi (bar) 313 ± 10% (22 ± 10%) at 2700 rpm
Weight Transfer Valve Pressure Setting (Adjustable)
psi (bar) 30–275 (2–19)
Hydrostatic Leakage Percentage Ranges 0–10% = Good
11–20% = Marginal
21% and Beyond = Bad
5-4 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Repair Specifications
Specification
Drive Shaft—Mounting Screw Torque lb-ft (N·m) 60–65 (81–88)
Drive Shaft—Yoke Screw Torque
lb-ft (N·m) 30–35 (41–47)
Traction Pump—Port “CP” Fitting Torque
lb-ft (N·m) 90 (122)
Traction Pump—Port “T” Fitting Torque
lb-ft (N·m) 110 (149)
Traction Pump—Port “A” Fitting Torque
lb-ft (N·m) 160 (217)
Traction Pump—Port “B” Fitting Torque
lb-ft (N·m) 160 (217)
Traction Pump—System Relief Valves Torque
lb-ft (N·m) 130 (176)
Traction Pump—Charge Pressure Relief Screw
Torque
lb-ft (N·m) 80 (108)
Traction Pump—Tow Valve Torque
lb-ft (N·m) 15 (20)
Traction Pump—Front Cover Screw Torque
lb-ft (N·m) 43 (58)
Traction Pump—Cover Plate Screw Torque
lb-ft (N·m) 57 (77)
Traction Pump—Auxiliary Pad Screw Torque
lb-ft (N·m) 32 (43)
Traction Pump—Case Outlet Plug Torque
lb-ft (N·m) 85 (115)
Traction Pump—Plug Torque
lb-ft (N·m) 15 (20)
Traction Pump—Servo Piston Cover Plug Torque
lb-ft (N·m) 27 (37)
Traction Pump—Servo Piston Cover Screw Torque
lb-ft (N·m) 11 (15)
Traction Pump—Seal Nut Torque
lb-ft (N·m) 27 (37)
Traction Pump—Filtration Cover Screw Torque
lb-ft (N·m) 22 (30)
Traction Pump—Filtration Cover Plug Torque
lb-ft (N·m) 27 (37)
4WD Valve—Check Valve Torque
lb-ft (N·m) 24–26 (32.6–35.4)
4WD Valve—4WD Oil Shuttle Torque
lb-ft (N·m) 46–54 (62.6–73.4)
4WD Valve—Hot Oil Shuttle Torque
lb-ft (N·m) 24–26 (32.6–35.4)
4WD Valve—4WD Reverse Solenoid Valve Torque
lb-ft (N·m) 46–54 (62.6–73.4)
4WD Valve—4WD Solenoid Valve Torque
lb-ft (N·m) 19–21 (25.8–28.6)
4WD Valve—Coil Nut Torque
lb-ft (N·m) 5 (6.8) Maximum
4WD Valve—Ports “1,” “2,” “3,” and “4” Fitting Torque
lb-ft (N·m) 100 (136)
4WD Valve—Ports “A” and “B” Fitting Torque
lb-ft (N·m) 140 (190)
4WD Valve—Port “T” Fitting Torque
lb-ft (N·m) 35 (47)
4WD Valve—Port “CP” Fitting Torque
lb-ft (N·m) 60 (81)
Front Wheel Motor—Case Drain Fitting Torque
lb-ft (N·m) 35 (47.5)
Left Front Wheel Motor—Tee Fitting Torque
lb-ft (N·m) 11 (15)
Front Wheel Motor—Inlet and Outlet Port Fitting
Torque
lb-ft (N·m) 140 (190)
Front Wheel Motor—Valving Cover Screw Torque
lb-ft (N·m) 88 (120)
Rear Wheel Motor—Mounting Screw Torque
lb-ft (N·m) 90 (122)
Rear Wheel Motor—Inlet and Outlet Port Fitting
Torque
lb-ft (N·m) 110 (149)
Rear Wheel Motor—Case Drain Fitting Torque
lb-ft (N·m) 15 (20.3)
Rear Wheel Motor—Front Retainer Screw Torque
lb-ft (N·m) 21 (28)
Rear Wheel Motor—Housing Screw Torque
lb-ft (N·m) 50 (68)
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-5
5
Hydraulic Hose, Tube, and
Fitting General Instructions
O-Ring Installation
• Always install new O-rings.
• On hoses with O-ring fittings, make sure O-rings are
properly seated before tightening.
• O-rings should be lubricated with the fluid to be used
in the system prior to assembly.
Boss Fitting O-Ring Installation
O-Ring Seal Kits
• SAE Boss O-Ring Kit Jacobsen PN 5002452
• O-Ring Face Seal (ORS) O-Ring Kit PN 5002454
• Common O-Ring Sizes Kit PN 5002453
Replacement O-Rings for ORS (Face Seal)
Fittings
Replacement O-Rings for O-Ring Boss
Fittings
Hydraulic Hose Installation
Hold the fixed portion of the hose coupling with one
wrench; use a second wrench to tighten or loosen the
hose nut. This will avoid damaging the fitting seal. When
tightening a hose, do not permit the hose to twist; hold
the hose in a normal straight position.
When installing hoses, place fittings at angles to avoid
contact with fixed parts when turning. Make sure hoses
are assembled to proper “A” and “B” ports on
components.
Hydraulic Hose and Tube Torque Values
1 Tubing O.D. or Hose I.D. 2 O-Ring 3 Thread Size
ORS (Face Seal)
Tube Size
ORS (Face Seal)
O-Ring Size
Jacobsen
Part
Number
4 11 339908
6 12 339909
8 14 339910
10 16 339911
12 18 339912
16 21 339913
20 25 339914
24 29 339915
TN4075
1
2
3
TN4097
Tubing O.D.
or Hose I.D.
Thread
Size
Jacobsen Part
Number
1/8 5/16-24 459290
3/16 3/8-24 459291
1/4 7/16-20 339896
5/16 1/2-20 459293
3/8 9/16-18 339897
1/2 3/4-16 339898
5/8 7/8-14 339899
3/4 1-1/16-12 339900
7/8 1-3/16-12 459296
1 1-5/16-12 339901
1-1/4 1-5/8-12 339902
1-1/2 1-7/8-12 339903
2 2-1/2-12 459300
Size lb-ft N·m
Dash Fractional Min Max Min Max
-4 1/4 10121416
-6 3/8 18202427
-8 1/2 32404354
-10 5/8 46 56 60 75
-12 3/4 65 80 90 110
-16 1 92 105 125 240
-20 1-1/4 125 140 170 190
-24 1-1/2 150 180 200 246
5-6 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Hydraulic Service Tools
NOTE
The hydraulic service tools listed here can be obtained
from K-Line Industries at http://klineind.com.
Portable In-Line Filter
Part Number JAC5097
When hydraulic components fail internally, debris from
the failed component can spread throughout the
hydraulic system and cause additional damage.
This situation can be magnified when dealing with a
closed-loop traction system, where oil is not filtered. In
the event of a traction system component failure, it is
recommended that all traction system components be
disassembled and cleaned, or filtered using a portable
in-line filter available through your Jacobsen Dealer. The
portable in-line filter should also be used when testing
hydraulic systems or after replacing a failed component.
IMPORTANT
Always install the in-line filter so oil flows through
the filter before entering a component. Once filtering
has begun, never reverse the flow of oil, or debris
will re-enter the system.
Digital Hydraulic Tester
Part Number AT40031
Features
• Flow up to 100 gpm (379 lpm)
• Pressure up to 6000 psi (414 bar)
• Temperature up to 250° F (120° C)
• Digital display for flow and temperature
• Analog display for pressure
• Flow accuracy 1% of full scale
Hydraulic Flow Meter
Part Number AT40002
Features
• Glycerin filled pressure gauge
• Precision needle-type load valve
• 4–40 gpm (15–15 lpm) flow range
• Pressure up to 5000 psi (345 bar)
• -12 port size
TN4286
TN4288
TN4287
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-7
5
Digital Pressure Gauge Kit
Part Number JAC5106
Features
• Quick disconnect fittings
• Pressure up to 5000 psi (345 bar)
• Includes one 5 ft (152 cm) hose
Hydraulic Hose Kit
Part Number JAC5001H
NOTE
This hydraulic hose kit is intended to be used with the
JAC5001A Hydraulic Test Fitting Kit.
Contents
• Two 8 ft (244 cm) 12 ORFS (F) x 10 ORFS (F) hoses
• Four 8 ft (244 cm) 10 ORFS (F) x 10 ORFS (F) hoses
• Two 8 ft (244 cm) 8 ORFS (F) x 10 ORFS (F) hoses
Flow Lock Tool
Part Number JAC5102
This adjustable flow lock tool is specifically designed for
use with the HR-9016T mower.
Hydraulic Test Fitting Kit
Part Number JAC5001A
NOTE
For detailed component descriptions and sizes, please
see the K-Line Industries website at http://klineind.com.
Contents
• Twenty ORFS tee fittings in five sizes
• Eight ORFS 90° elbow fittings in four sizes
• Forty ORFS caps in five sizes
• Forty ORFS plugs in five sizes
• Six ORS reducer adapters in three sizes
• Sixteen ORS adapters in four sizes
• Eight blocking disks in four sizes
• Three JIC tee fittings in three sizes
• Three 4 in. (102 mm) jumper hoses in three sizes
• One ORS/male NPTF adapter
• One vented bushing
• One copper tube assembly
Blocking Disk Set
Part Number JAC5001-1
NOTE
This blocking disk set is part of the JAC5001A Hydraulic
Test Fitting Kit.
Contents
• Two -6 blocking disks
• Two -8 blocking disks
• Two -10 blocking disks
• Two -12 blocking disks
• Two -16 blocking disks
TN4290
TN4291
TN4289
5-8 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Component Location
See Figure 5-1.
Figure 5-1: Component Location—Left Side
1Traction Pump 34WD Valve 5Front Wheel Motor
2 2-Section Pump 4 Rear Wheel Motor
TN4274, TN4139, TN4275, TN4082
1
3
2
5
4
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-9
5
Theory of Operation and
Sub-Circuit Schematics
Traction Circuit—Neutral Schematic
and Theory of Operation
System Conditions:
• Operator in seat
• Engine running
• Park brake released
• Traction pedal in the neutral position
Charge Pressure Circuit
The traction pump, 2-section pump, and 3-section pump
are all driven by the engine. Section 2 of the 2-section
pump provides charge pressure oil through the left front
deck valve for the traction circuit.
Hydraulic oil is drawn from the hydraulic oil tank by
section 2 of the 2-section pump. Before entering the
2-section pump, the inlet oil is filtered by a 100-mesh
screen to remove any debris. Charge pressure oil from
section 2 of the 2-section pump is routed to port “P” of the
left front deck valve. Oil entering port “P” of the left front
deck valve flows through the solenoid valve and out port
“T” of the left front deck valve.
Oil from port “T” of the left front deck valve is routed to
the charge filter. If the charge filter becomes plugged, a
25 psi (1.7 bar) pressure differential switch will activate
the “Hydraulic Filter” light on the instrument panel
warning light gauge and the charge filter will be
bypassed. Charge pressure oil from the charge filter is
routed to port “CP” of the traction pump to fill the
closed-loop traction circuit. Once filled, the 313 psi (21.6
bar) charge pressure relief valve will open, allowing oil to
return to the return manifold, and then to the hydraulic
tank.
Traction Pump Circuit
With the traction pedal in the neutral position, the
displacement control valve is in the neutral position and
oil pressure in both pilot lines to the control sleeve is
equal. Since pressure is equal on both sides of the
control sleeve, the control sleeve is centered in the
neutral position. Oil is not supplied to the servo pistons
and no movement of the swashplate occurs.
The charge oil is supplied to the closed-loop traction
circuit via the check valves and exits the traction pump at
ports “A” and “B.” Oil from port “A” is routed in parallel to
the front wheel motors and to port “B” of the 4WD valve.
Oil from port “B” of the traction pump is routed in parallel
to the front wheel motors and to port “A” of the 4WD
valve. Since pressure is equal on each side of the front
wheel motors, no movement occurs.
Hydraulic oil is used to lubricate the internal components
of pumps and motors. This oil is returned via the case
drain lines back to the return manifold, and then to the
hydraulic tank.
5-10 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Traction Circuit—Neutral Schematic
See Figures 5-2 and 5-3.
Figure 5-2
1 Charge Pressure Oil to Front
Wheel Motors
5 Case Drain Oil from Front Wheel Motors 9 Case Drain Oil from Right Rear Wheel Motor
and Return Oil from Piston End of LH Front Lift
Cylinder
2 Charge Pressure Oil to Front
Wheel Motors
6 Return Oil from 4WD Valve (Port T) 10 Return Oil from Steering Unit (Port T)
3 Charge Pressure Oil to Left Front
Deck Valve (Port P)
7 Case Drain Oil from Left Rear Wheel Motor 11 Charge Pressure Oil from Left Front Deck
Valve (Port T)
4 Charge Pressure Oil to 4WD Valve
(Port CP)
8 Case Drain Oil from Front Deck Motors
Traction Pump
Oil
Cooler
Return
Oil Filter
Return
Manifold
100 Mesh
Screen
Screen
100 Mesh
Hydraulic Oil Tank
Charge
Filter
Tank Fill Cap
Assembly
Tow
Valve
Charge Pressure
Relief Valve
313 psi
Reverse
Relief
Valve
4387 psi
2.81
ci
B
CP
A
0.036 in.
0.031 in.
0.031 in.
T
60 psi
Crack
Bypass
10 Micron
25 psi
Crack
Bypass
10 Micron
10 Micron
Check
Valve
Filter
2.9 psi
Crack
Bypass
Displacement
Control
Valve
CW
CCW
Pump
2-Section
Pump
Check
Valve
Check
Valve
Forward
Relief
Valve
4387 psi
Engine
2700
rpm
Forward
Reverse
25 psi
Crack
Bypass
1
2
3
4
6
7
8
9
10
11
5
3-Section Pump
25 psi
Pressure
Differential
Switch
1.28
ci ci
0.49
21
1.28
ci
1.28
ci ci
1.28
321
TN4035
Return Oil
Charge Pressure Oil
Metered Oil
Inlet or Drain Oil
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-11
5
Traction Circuit—Neutral Schematic,
Continued
Figure 5-3
1 Charge Pressure Oil from Traction
Pump (Port B)
5 Front Wheel Motors Case Drain Oil to Return
Manifold
8 Front Deck Motors Case Drain Oil to
Return Manifold
2 Charge Pressure Oil from Traction
Pump (Port A)
6 4WD Valve (Port T) Return Oil to Return Manifold 9 Right Rear Wheel Motor Case Drain Oil
and LH Front Lift Cylinder Piston End Oil
to Return Manifold
3 Charge Pressure Oil from 2-Section
Pump (Section 2)
7 Left Rear Wheel Motor Case Drain Oil to Return
Manifold
11 Charge Pressure Oil to Charge Filter
4 Charge Pressure Oil from Charge
Filter
1
2
3
4
6
7
8
9
11
5
L
L
R
R
DA
DB
DC
Right Front
Wheel
Motor
4WD Valve
Left
Rear
Wheel
Motor
ci
12.54
ci
12.54
A
BA
B
4WD
Solenoid
Valve
Hot Oil
Shuttle
4WD Oil
Shuttle
A
T
CP
B
1
4
3
2
15.56
cici
15.56
0.059
in.
4WD
Reverse
Solenoid
Valve
Right
Rear
Wheel
Motor
Check
Valve
Left Front
Wheel
Motor
Left
Front
Deck
Valve
Left
Center
Motor
Left
Winglet
Motor
Check
Valve
AB
PD T
Relief Valve
3000 psi
Blade
Brake
Relief
Valve
630 psi
Test
Port
Check
Valve
0.98
ci
0.98
ci
Solenoid
Valve
TN4036
Return Oil
Charge Pressure Oil
5-12 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Page Intentionally Blank
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-13
5
Traction Circuit—Forward 4WD
Schematic and Theory of Operation
System Conditions:
• Engine running
• Park brake released
• Traction pedal in the forward position
• 4WD switch in the 4WD position
Charge Pressure Circuit
The traction pump, 2-section pump, and 3-section pump
are all driven by the engine. Section 2 of the 2-section
pump provides charge pressure oil through the left front
deck valve for the traction circuit.
Hydraulic oil is drawn from the hydraulic oil tank by
section 2 of the 2-section pump. Before entering the
2-section pump, the inlet oil is filtered by a 100-mesh
screen to remove any debris. Charge pressure oil from
section 2 of the 2-section pump is routed to port “P” of the
left front deck valve. Oil entering port “P” of the left front
deck valve flows through the solenoid valve and out port
“T” of the left front deck valve.
Oil from port “T” of the left front deck valve is routed to
the charge filter. If the charge filter becomes plugged, a
25 psi (1.7 bar) pressure differential switch will activate
the “Hydraulic Filter” light on the instrument panel
warning light gauge and the charge filter will be
bypassed. Charge pressure oil from the charge filter is
routed to port “CP” of the traction pump to fill the
closed-loop traction circuit. Once filled, the 313 psi (21.6
bar) charge pressure relief valve will open, allowing oil to
return to the return manifold, and then to the hydraulic
tank. Charge pressure oil from the charge filter is also
routed to port “CP” of the 4WD valve.
Traction Drive Circuit
When the traction pedal is moved to the forward position,
the displacement control valve is moved to the forward
position.
Charge pressure oil is supplied to the 0.036 in. (0.91 mm)
orifice. Oil is then routed to the displacement control
valve. With the displacement control valve in the forward
position, oil flows through the displacement control valve
and through the 0.031 in. (0.79 mm) orifice to the control
sleeve. Oil is then routed to the forward side of the servo
piston and the swashplate is moved to the forward
direction. This change of the swashplate angle produces
an increase of oil flow on one side of the pump.
Operating pressure oil is then routed to the check valve
and 4387 psi (302 bar) forward relief valve, and exits the
traction pump through port “B.” Oil is then routed in
parallel to the front wheel motors, driving the motors in
the forward direction. Operating pressure oil is also
routed to port “A” of the 4WD valve. Oil exiting the front
wheel motors is returned to the traction pump to
replenish the intake side of the pump.
Charge pressure oil entering port “CP” of the 4WD valve
is routed to the 4WD solenoid valve and to test port “DC.”
Charge pressure oil entering port “CP” is also routed
through the check valve and to the 4WD reverse solenoid
valve and 4WD oil shuttle.
When the 4WD switch is placed in the 4WD position, the
4WD solenoid valve shifts, allowing oil to flow through the
valve. This charge pressure oil is then routed to the pilot
end of the 4WD oil shuttle, causing the valve to shift. With
the valve shifted, operating pressure oil from port “A”
flows through the 4WD oil shuttle, and is routed in
parallel through port “1” of the 4WD valve to the right rear
wheel motor and through port “2” of the 4WD valve to the
left rear wheel motor, driving the rear wheels in the
forward direction.
Oil exiting the rear wheel motors enters the 4WD valve at
ports “3” (right rear wheel motor) and “4” (left rear wheel
motor), and flows through the 4WD reverse solenoid
check valve and exits the 4WD valve at port “B” to
replenish the intake side of the traction pump.
Charge pressure oil from the check valve also flows
through the 4WD reverse solenoid check valve, exiting
the 4WD valve at port “B” to replenish the intake side of
the traction pump. With the 4WD oil shuttle shifted,
charge pressure oil from the check valve to the 4WD oil
shuttle is blocked.
Hot Oil Shuttle
The hot oil shuttle is used to remove hot oil from the
closed-loop traction drive circuit when driving either
forward or in reverse. Oil lost due to venting through the
hot oil shuttle is replenished by return oil from the rear
wheel motors and charge oil from port “CP.”
When driving forward, operating pressure oil from port
“A” of the 4WD valve is routed to the pilot line on the
forward side of the hot oil shuttle, shifting the valve spool.
Hot oil from the rear wheel motors and charge oil from
the check valve flows through the 4WD reverse solenoid
valve, through the hot oil shuttle, through the 0.059 in.
(1.5 mm) orifice, and is routed back to the return
manifold, and then to the hydraulic tank.
Circuit Relief
The forward side of the traction circuit is protected by the
forward relief valve. The relief valve will open if the
pressure rises to 4387 psi (302 bar), allowing oil to dump
to the charge side of the circuit.
5-14 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Traction Circuit—Forward 4WD Schematic
See Figures 5-4 and 5-5.
Figure 5-4
1 Operating Pressure Oil to Front
Wheel Motors
5 Case Drain Oil from Front Wheel Motors 9 Case Drain Oil from Right Rear Wheel Motor
and Return Oil from Piston End of LH Front Lift
Cylinder
2 Charge Pressure Oil from Front
Wheel Motors
6 Return Oil from 4WD Valve (Port T) 10 Return Oil from Steering Unit (Port T)
3 Charge Pressure Oil to Left Front
Deck Valve (Port P)
7 Case Drain Oil from Left Rear Wheel Motor 11 Charge Pressure Oil from Left Front Deck
Valve (Port T)
4 Charge Pressure Oil to 4WD Valve
(Port CP)
8 Case Drain Oil from Front Deck Motors
Traction Pump
Oil
Cooler
Return
Oil Filter
Return
Manifold
100 Mesh
Screen
Screen
100 Mesh
Hydraulic Oil Tank
Charge
Filter
Tank Fill Cap
Assembly
Tow
Valve
Charge Pressure
Relief Valve
313 psi
Reverse
Relief
Valve
4387 psi
2.81
ci
B
CP
A
0.036 in.
0.031 in.
0.031 in.
T
60 psi
Crack
Bypass
10 Micron
25 psi
Crack
Bypass
10 Micron
10 Micron
Check
Valve
Filter
2.9 psi
Crack
Bypass
Displacement
Control
Valve
CW
CCW
Pump
2-Section
Pump
Check
Valve
Check
Valve
Forward
Relief
Valve
4387 psi
Engine
2700
rpm
Forward
Reverse
25 psi
Crack
Bypass
1
2
3
4
6
7
8
9
10
11
5
3-Section Pump
25 psi
Pressure
Differential
Switch
1.28
ci ci
0.49
21
1.28
ci
1.28
ci ci
1.28
321
TN4037
Operating Pressure Oil Return Oil
Charge Pressure Oil
Metered Oil
Inlet or Drain Oil
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-15
5
Traction Circuit—Forward 4WD Schematic,
Continued
Figure 5-5
1 Operating Pressure Oil from
Traction Pump (Port B)
5 Front Wheel Motors Case Drain Oil to Return
Manifold
8 Front Deck Motors Case Drain Oil to
Return Manifold
2 Charge Pressure Oil to Traction
Pump (Port A)
6 4WD Valve (Port T) Return Oil to Return Manifold 9 Right Rear Wheel Motor Case Drain Oil
and LH Front Lift Cylinder Piston End Oil
to Return Manifold
3 Charge Pressure Oil from 2-Section
Pump (Section 2)
7 Left Rear Wheel Motor Case Drain Oil to Return
Manifold
11 Charge Pressure Oil to Charge Filter
4 Charge Pressure Oil from Charge
Filter
1
2
3
4
6
7
8
9
11
5
L
L
R
R
DA
DB
DC
Right Front
Wheel
Motor
4WD Valve
Left
Rear
Wheel
Motor
ci
12.54
ci
12.54
A
BA
B
4WD
Solenoid
Valve
Hot Oil
Shuttle
4WD Oil
Shuttle
A
T
CP
B
1
4
3
2
15.56
cici
15.56
0.059
in.
4WD
Reverse
Solenoid
Valve
Right
Rear
Wheel
Motor
Check
Valve
Left Front
Wheel
Motor
Left
Front
Deck
Valve
Left
Center
Motor
Left
Winglet
Motor
Check
Valve
AB
PD T
Relief Valve
3000 psi
Test
Port
Check
Valve
0.98
ci
0.98
ci
Solenoid
Valve
Blade
Brake
Relief
Valve
630 psi
TN4038
Operating Pressure Oil
Return Oil
Charge Pressure Oil
Inlet or Drain Oil
5-16 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Page Intentionally Blank
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-17
5
Traction Circuit—Reverse 4WD
Schematic and Theory of Operation
System Conditions:
• Engine running
• Park brake released
• Traction pedal in the reverse position
• 4WD switch in the 4WD position
• 4WD reverse switch in the momentary 4WD reverse
position
Charge Pressure Circuit
The traction pump, 2-section pump, and 3-section pump
are all driven by the engine. Section 2 of the 2-section
pump provides charge pressure oil through the left front
deck valve for the traction circuit.
Hydraulic oil is drawn from the hydraulic oil tank by
section 2 of the 2-section pump. Before entering the
2-section pump, the inlet oil is filtered by a 100-mesh
screen to remove any debris. Charge pressure oil from
section 2 of the 2-section pump is routed to port “P” of the
left front deck valve. Oil entering port “P” of the left front
deck valve flows through the solenoid valve and out port
“T” of the left front deck valve.
Oil from port “T” of the left front deck valve is routed to
the charge filter. If the charge filter becomes plugged, a
25 psi (1.7 bar) pressure differential switch will activate
the “Hydraulic Filter” light on the instrument panel
warning light gauge and the charge filter will be
bypassed. Charge pressure oil from the charge filter is
routed to port “CP” of the traction pump to fill the
closed-loop traction circuit. Once filled, the 313 psi (21.6
bar) charge pressure relief valve will open, allowing oil to
return to the return manifold, and then to the hydraulic
tank.
Traction Drive Circuit
When the traction pedal is moved to the reverse position,
the displacement control valve is moved to the reverse
position.
Charge pressure oil is supplied to the 0.036 in. (0.91 mm)
orifice. Oil is then routed to the displacement control
valve. With the displacement control valve in the reverse
position, oil flows through the displacement control valve
and through the 0.031 in. (0.79 mm) orifice to the control
sleeve. Oil is then routed to the reverse side of the servo
piston and the swashplate is moved to the reverse
direction. This change of the swashplate angle produces
an increase of oil flow on one side of the pump.
Operating pressure oil is then routed to the check valve
and 4387 psi (302 bar) reverse relief valve, and exits the
traction pump through port “A.” Oil is then routed in
parallel to the front wheel motors, driving the motors in
the reverse direction. Operating pressure oil is also
routed to port “B” of the 4WD valve. Oil exiting the front
wheel motors is returned to the traction pump to
replenish the intake side of the pump.
Charge pressure oil entering port “CP of the 4WD valve
is routed to the 4WD solenoid valve, test port “DC,” and
the check valve.
When the 4WD switch is placed in the 4WD position, the
4WD solenoid valve shifts, allowing oil to flow through the
valve. This charge pressure oil is then routed to the pilot
end of the 4WD oil shuttle, causing the valve to shift.
Operating pressure oil entering port “B” of the 4WD valve
is routed to the hot oil shuttle, test port “DB,” and the
4WD reverse solenoid valve.
When the 4WD reverse switch is held in the momentary
4WD reverse position, the 4WD reverse solenoid shifts.
With the valve shifted, operating pressure oil from port
“B” flows through the valve and is routed to the check
valve, 4WD oil shuttle, and is then routed in parallel
through port “3” of the 4WD valve to the right rear wheel
motor and through port “4” of the 4WD valve to the left
rear wheel motor, driving the rear wheels in the reverse
direction.
Oil exiting the rear wheel motors enters the 4WD valve at
ports “1” (right rear wheel motor) and “2” (left rear wheel
motor), and flows to the 4WD oil shuttle. With the 4WD oil
shuttle shifted, return oil from the rear wheel motors flows
through the 4WD oil shuttle and is routed to the hot oil
shuttle, test port “DA,” and then exits the 4WD valve at
port “A” to replenish the intake side of the traction pump.
Hot Oil Shuttle
The hot oil shuttle is used to remove hot oil from the
closed-loop traction drive circuit when driving either
forward or in reverse. Oil lost due to venting through the
hot oil shuttle is replenished by return oil from the rear
wheel motors.
When driving in reverse, operating pressure oil from port
“B” of the 4WD valve is routed to the pilot line on the
reverse side of the hot oil shuttle, shifting the valve spool.
Hot oil from the rear wheel motors flows through the 4WD
hot oil shuttle, through the 0.059 in. (1.5 mm) orifice, and
is routed back to the return manifold, and then to the
hydraulic tank.
Circuit Relief
The reverse side of the traction circuit is protected by the
reverse relief valve. The relief valve will open if the
pressure rises to 4387 psi (302 bar), allowing oil to dump
to the charge side of the circuit.
5-18 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
Traction Circuit—Reverse 4WD Schematic
See Figures 5-6 and 5-7.
Figure 5-6
1 Charge Pressure Oil from Front
Wheel Motors
5 Case Drain Oil from Front Wheel Motors 9 Case Drain Oil from Right Rear Wheel Motor
and Return Oil from Piston End of LH Front Lift
Cylinder
2 Operating Pressure Oil to Front
Wheel Motors
6 Return Oil from 4WD Valve (Port T) 10 Return Oil from Steering Unit (Port T)
3 Charge Pressure Oil to Left Front
Deck Valve (Port P)
7 Case Drain Oil from Left Rear Wheel Motor 11 Charge Pressure Oil from Left Front Deck
Valve (Port T)
4 Charge Pressure Oil to 4WD Valve
(Port CP)
8 Case Drain Oil from Front Deck Motors
Traction Pump
Oil
Cooler
Return
Oil Filter
Return
Manifold
100 Mesh
Screen
Screen
100 Mesh
Hydraulic Oil Tank
Charge
Filter
Tank Fill Cap
Assembly
Tow
Valve
Charge Pressure
Relief Valve
313 psi
Reverse
Relief
Valve
4387 psi
2.81
ci
B
CP
A
0.036 in.
0.031 in.
0.031 in.
T
60 psi
Crack
Bypass
10 Micron
25 psi
Crack
Bypass
10 Micron
10 Micron
Check
Valve
Filter
2.9 psi
Crack
Bypass
Displacement
Control
Valve
CW
CCW
Pump
2-Section
Pump
Check
Valve
Check
Valve
Forward
Relief
Valve
4387 psi
Engine
2700
rpm
Forward
Reverse
25 psi
Crack
Bypass
1
2
3
4
6
7
8
9
10
11
5
25 psi
Pressure
Differential
Switch
1.28
ci ci
0.49
21
3-Section Pump
1.28
ci
1.28
ci ci
1.28
321
TN4039
Operating Pressure Oil Return Oil
Charge Pressure Oil
Metered Oil
Inlet or Drain Oil
HYDROSTATIC POWER TRAIN
4263110-Rev B 5-19
5
Traction Circuit—Reverse 4WD Schematic,
Continued
Figure 5-7
1 Charge Pressure Oil to Traction
Pump (Port B)
5 Front Wheel Motors Case Drain Oil to Return
Manifold
8 Front Deck Motors Case Drain Oil to
Return Manifold
2 Operating Pressure Oil from
Traction Pump (Port A)
6 4WD Valve (Port T) Return Oil to Return Manifold 9 Right Rear Wheel Motor Case Drain Oil
and LH Front Lift Cylinder Piston End Oil
to Return Manifold
3 Charge Pressure Oil from 2-Section
Pump (Section 2)
7 Left Rear Wheel Motor Case Drain Oil to Return
Manifold
11 Charge Pressure Oil to Charge Filter
4 Charge Pressure Oil from Charge
Filter
1
2
3
4
6
7
8
9
11
5
L
L
R
R
CP
DB
DC
Blade
Brake
Relief
Valve
630 psi
Right Front
Wheel
Motor
4WD Valve
Left
Rear
Wheel
Motor
ci
12.54
ci
12.54
A
BA
B
4WD
Solenoid
Valve
Hot Oil
Shuttle
4WD Oil
Shuttle
A
T
B
1
4
3
2
15.56
cici
15.56
0.059
in.
4WD
Reverse
Solenoid
Valve
Right
Rear
Wheel
Motor
Check
Valve
Left Front
Wheel
Motor
Left
Front
Deck
Valve
Left
Center
Motor
Left
Winglet
Motor
Check
Valve
AB
PD T
Relief Valve
3000 psi
Test
Port
Check
Valve
0.98
ci
0.98
ci
Solenoid
Valve
TN4040
Operating Pressure Oil
Return Oil
Charge Pressure Oil
Inlet or Drain Oil
5-20 4263110-Rev B
HYDROSTATIC POWER TRAIN
5
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