- Lockup clutch
engaged
- Output shaft rotates at engine rpm - Stator freewheels
STATOR
TORQUE CONVERTER
DIRECT DRIVE
TORQUE CONVERTER LOCKUP OIL PASSAGE STATOR
FREEWHEEL ASSEMBLY
TORQUE CONVERTER INLET OIL
In DIRECT DRIVE, the lockup clutch is engaged by hydraulic pressure and locks the turbine to the impeller. The housing, impeller, turbine, and output shaft then rotate as a unit at engine rpm. The stator, which is mounted on a freewheel assembly, is driven by the force of the oil in the housing and will freewheel at approximately the same rpm.
1. Transfer gears 2. Transmission 3. Differential
84
2
1 3
Power flows from the torque converter through a drive shaft to the transfer gears (1). The transfer gears are splined to the transmission.
The transmission (2) is located between the transfer gears and the differential (3). The transmission is electronically controlled and
hydraulically operated like all other ICM (Individual Clutch Modulation) transmissions in Caterpillar rigid frame trucks.
The differential is located in the rear axle housing behind the
transmission. Power from the transmission flows through the differential and is divided equally to the final drives in the rear wheels. The final drives are double reduction planetaries.
85
• Transmission is power shift planetary design
1 2 3
4
5 6
POWER SHIFT PLANETARY TRANSMISSION
The transmission is a power shift planetary design which contains six hydraulically engaged clutches. The transmission provides six FORWARD speeds and one REVERSE speed.
1. Rear axle oil pump
86
1
2 3
4
Shown is the differential removed from the rear axle housing. The rear axle cooling and filter system starts with a rear axle oil pump (1) that is driven by the differential. Since the pump rotates only when the machine is moving, no oil flow is produced when the machine is stationary.
Cooling oil flow increases with ground speed to provide cooling when it is most needed.
The rear axle pump pulls oil from the bottom of the rear axle housing through a suction screen (2). Oil flows from the pump through a temperature and flow control valve located on top of the differential housing to a filter mounted on the rear of the axle housing. Oil then flows from the filter back to the valve located on top of the differential housing.
Oil then flows from the valve to the rear wheel bearings and the differential bearings.
Oil flows through tubes (3) to the differential bearings.
The fiberglass shroud (4) reduces the temperature of the rear axle oil on long hauls by reducing the oil being splashed by the bevel gear.
2. Rear axle suction screen
3. Differential bearing oil tubes
4. Fiberglass shroud
1. Differential oil temperature sensor 2. Rear axle
temperature and flow control valve
87
2
4 1
3
Oil flows from the pump past the differential oil temperature sensor (1) to the rear axle temperature and flow control valve (2). The differential oil temperature sensor provides an input signal to the VIMS.
The temperature sensor input signal is used to warn the operator of a high rear axle oil temperature condition or to turn on the attachment rear axle cooling fan (if equipped).
Oil flows from the temperature and flow control valve to the differential oil filter (3) mounted on the rear of the axle housing. Oil then flows from the filter back to the temperature and flow control valve. Some of the oil that flows from the temperature and flow control valve flows through the small supply hose (4) to the differential bearings.
3. Differential oil filter
4. Differential bearing oil supply hose
1. Differential oil filter restriction switch 2. Rear axle oil level
switches
88 2
1
3 2
The differential oil filter restriction switch (1) and the two rear axle oil level switches (2) provide input signals to the VIMS.
The differential oil filter restriction switch signal is used to warn the operator when the differential oil filter is plugged.
The rear axle oil level switch input signals are used to warn the operator when the rear axle oil level is LOW.
When the truck is initially put into operation, a 1R0719 (40 micron) filter is installed. This filter removes the rust inhibitor used during
manufacturing. The 40 micron filter should be changed after the first 50 hours of operation and replaced with a 4T3131 (13 micron) filter. The 13 micron filter should be changed every 500 hours.
A differential carrier thrust pin is located behind the small cover (3). The thrust pin prevents movement of the differential carrier during high thrust load conditions.
3. Differential carrier thrust pin cover
• Differential oil filter service information
1. Differential oil pressure sensor
89 1 2
The differential oil pressure sensor (1) provides an input signal to the VIMS. The differential oil pressure sensor signal is used to warn the operator of a HIGH or LOW rear axle oil pressure condition.
A LOW oil pressure warning is provided if the pressure is below 35 kPa (5 psi) when the differential oil temperature is above 52°C (125°F) and the ground speed is higher than 24 km/h (15 mph).
A HIGH oil pressure warning is provided if the pressure is above 690 kPa (100 psi) when the differential oil temperature is above 52°C (125°F).
The temperature and pressure control valve (2) prevents high oil pressure when the rear axle oil is cold. When the oil temperature is below 43°C (110°F), the valve is OPEN and allows oil to flow to the rear axle housing. When the oil temperature is above 43°C (110°F), the valve is CLOSED and all the oil flows through the filter to a flow control valve located in the temperature and flow control valve. The temperature and pressure control valve is also the system main relief valve. If the pressure exceeds 690 kPa (100 psi), the temperature and pressure control valve will open to prevent high oil pressure to the rear axle oil filter.
The flow control valve distributes the oil flow to the rear wheel bearings and the differential bearings.
2. Temperature and pressure control valve
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