POWER TRAIN COMPONENTS
POWER TRAIN ELECTRICAL SYSTEM
ride control is active. Either in AUTO mode when driving above the threshold speed or when in service mode.
Clutch solenoids: The solenoids control the oil flow through the respective speed and directional modulating valves.
Secondary steering intermediate relay: The Power Train ECM energizes the relay when the loss of steering pressure is detected by the Power Train ECM. The ECM energizes the relay and power is supplied to the secondary steering pump.
Back-up alarm: The Power Train ECM energizes the back-up alarm when the operator selects the REVERSE direction.
Heated mirror relay: The Power Train ECM energizes the relay to send current to the coil to warm the mirror.
Ride Control Solenoid valve (RE): The Power Train ECM energizes the solenoid valve that controls the opening of the antidrift valve which allows flow between the rod end of the lift cylinders and tank.
Ride Control Solenoid valve (HE): The Power Train ECM energizes the solenoid valve that controls the opening of the antidrift valve which allows flow between the accumulator and the head end of the lift cylinders.
Ride Control Solenoid valve (Balance): At engine start-up, the Power Train ECM energizes the solenoid valve 2. When the Power Train ECM recognizes the ground speed in AUTO reaches the default threshold speed value in the Power Train ECM, the ECM de-energizes the ride control balance solenoid valve for a default time designated through Caterpillar ET
configuration. The pressure between the head end of the lift cylinders and the accumulator are balanced. Then, the Power Train ECM energizes the head end ride control solenoid valve and rod end ride control solenoid valve.
Back-up Alarm
The back-up alarm (arrow) is located on the right hand side of the machine inside the access door. The alarm sounds when the transmission directional switch is placed in the REVERSE position.
Warning Panel - Left Side
This illustration shows the warning panel on the left side of the dash panel. These indicators are driven outputs of the Power Train ECM.
The transmission oil filter bypass (1) is located on the top right hand side. This alarm is illuminated when the transmission oil filter is bypassing due to a plugged filter requiring a change.
The transmission neutralizer disabled indicator (2) is located in the center of the panel. This indicator is illuminated when the transmission neutralized is disabled.
The low fuel filter WARNING indicator (3) is located in the center row on the right side. This indicator is illuminated when the fuel level is below 10% of the total fuel tank volume. The ride control SERVICE indicator (4) is located in the bottom row on left side. This indicator is illuminated when the ride control switch is placed in the SERVICE position. The ride control AUTO indicator (5) is located in the bottom row, center. This indicator is illuminated when the ride control switch is placed in the AUTO position.
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Implement Control Valve - With Ride Control
The ride control system is an option on the 966H and the 972H Wheel Loaders. The optional ride control system provides a means for dampening the bucket forces, which produce a pitching motion as the machine travels over rough terrain. The operation of ride control is initiated by the switch input to the Power Train ECM with outputs to the solenoid valves on the implement control valve (1).
On the implement control valve, there are two solenoid valves that controls oil flow over the antidrift valves and one solenoid valve controlling the shifting of the balance valve. Energizing solenoid valve (2) provides a path of oil between the head end of the lift cylinders and the ride control accumulator. Energizing solenoid valve (3) allows the balance spool to shift as the solenoid valve provides a path for the oil on the end of the balance spool to flow to the hydraulic tank passage. Energizing solenoid valve (4) drains the oil pressure off the antidrift valve enabling the valve to raise. Supply oil flows between the rod end of the lift cylinders and the hydraulic tank.
The optional ride control is enabled through the Machine Configuration screen with Caterpillar Electronic Technician (ET). When the ride control system is in SERVICE/AUTO, the
respective LED is illuminated on the machine status display.
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Secondary Steering Intermediate Relay
The secondary steering intermediate relay (1) is an output of the Power Train ECM. When the steering oil pressure at the primary pressure goes below the value of the pressure switch (2), a signal is sent to the Power Train ECM. Then, the ECM sends current to the intermediate relay to energize the secondary steering pump motor. The secondary steering pump will supply oil to the steering system.
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Engine Start Relay
The engine start relay (2) is located in the left side service center (1). The engine start relay is energized by the Power Train ECM when all the engine starting requirements are met. When the relay is energized, battery voltage flows through the relay to the starter solenoid.
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Transmission Hydraulic System - NEUTRAL
This illustration shows the transmission hydraulic system with the engine running and the transmission shift lever in the NEUTRAL position.
When the engine is running, flow from the pump is sent through the filter to the six
transmission solenoid valves. Pump flow is also sent to the transmission relief valve. The transmission relief valve limits the transmission oil pressure to the modulating valves. When NEUTRAL is selected, the Power Train ECM energizes the No. 3 solenoid. The modulating valve controls the flow of oil to the No. 3 clutch.
When the No. 3 solenoid is energized, the electromagnetic force moves the pin against the ball. The ball moves to the right against the seat. The oil flow through the center of the valve spool is blocked. The oil pressure increases at the left end of the valve spool and the valve spool moves to the right against the spring. Then, oil flow is directed to the ports for clutch 3.
From the main relief valve, oil flows to the torque converter and the torque converter inlet relief valve. The torque converter inlet relief valve limits the oil pressure to the torque converter. When oil pressure to the torque converter exceeds 900 ± 70 kPa (130 ± 10 psi), the inlet relief valve opens and sends the excess oil pressure to drain.
Torque Converter Inlet Relief Valve Filter Transmission Pump Tank Main Relief Valve
Torque Converter Power Train ECM 4 5 6 2 1 Torque Converter Outlet Relief Valve
To Transmission Bearing Lubrication 3 2 3 Modulating Valve Modulating Valve Modulating Valve Modulating Valve Screen Group Magnet FORWARD FOURTH SPEED SECOND SPEED 4 Modulating Valve THIRD SPEED 5 6 FIRST SPEED Modulating Valve 1 REVERSE Cooler
Oil in the torque converter flows out of the torque converter through the torque converter outlet relief valve. The outlet relief valve maintains the pressure in the torque converter at a
minimum of 415 ± 135 kPa (60 ± 20 psi) at torque converter stall rpm.
From the torque converter outlet relief valve, the oil flows through the transmission oil cooler and on to the transmission for cooling and lubrication of the bearings and planetary.
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This illustration shows the transmission hydraulic system with the engine running and the transmission shift lever in the FORWARD position and the speed selector in FIRST SPEED. When the engine is running, flow from the pump is sent through the filter to the six
transmission solenoid valves. Pump flow is also sent to the transmission relief valve. The transmission relief valve limits the transmission oil pressure to the modulating valves. When FIRST SPEED FORWARD is selected, the Power Train ECM energizes the No. 2
solenoid and the No. 6 solenoid. The modulating valve controls the flow of oil to the No. 2 and No. 6 clutches.
When the No. 2 and No. 6 solenoids are energized, the electromagnetic force moves the
armature against the ball. The ball moves to the right against the seat. The oil flow through the center of the valve spool is blocked. The oil pressure increases at the left end of the valve spool and the valve spool moves to the right against the spring. Then, oil flow is directed to the ports for clutch 2 and clutch 6.
From the main relief valve, oil flows to the torque converter and the torque converter inlet relief valve. The torque converter inlet relief valve limits the oil pressure to the torque converter. When oil pressure to the torque converter exceeds 900 ± 70 kPa (130 ± 10 psi), the inlet relief valve opens and sends the excess oil pressure to drain.
6 Torque Converter Inlet Relief Valve Filter Transmission Pump Tank Main Relief Valve
Torque Converter Power Train ECM 4 5 3 3 Modulating Valve 1 Torque Converter Outlet Relief Valve
To Transmission Bearing Lubrication Modulating Valve 1 4 Modulating Valve Screen Group Magnet Cooler 2 2 Modulating Valve FORWARD REVERSE THIRD SPEED FOURTH SPEED Modulating Valve FIRST SPEED 5 Modulating Valve SECOND SPEED 6
Oil in the torque converter flows out of the torque converter through the torque converter outlet relief valve. The outlet relief valve maintains the pressure in the torque converter at a
minimum of 415 ± 135 kPa (60 ± 20 psi) at torque converter stall rpm.
From the torque converter outlet relief valve, the oil flows through the transmission oil cooler and then to the transmission for cooling and lubrication of the bearings and planetary.
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This illustration shows the transmission hydraulic system with the engine running and the transmission shift lever in the FORWARD position and the speed selector in SECOND SPEED. When the engine is running, flow from the pump is sent through the filter to the six
transmission solenoid valves. Pump flow is also sent to the transmission relief valve. The transmission relief valve limits the transmission oil pressure to the modulating valves. When FIRST SPEED FORWARD is selected, the Power Train ECM energizes the No. 2
solenoid and the No. 5 solenoid. The modulating valve controls the flow of oil to the No. 2 and No. 5 clutches.
When the No. 2 and No. 5 solenoids are energized, the electromagnetic force moves the
armature against the ball. The ball moves to the right against the seat. The oil flow through the center of the valve spool is blocked. The oil pressure increases at the left end of the valve spool and the valve spool moves to the right against the spring. Then, oil flow is directed to the ports for clutch 2 and clutch 5.
From the main relief valve, oil flows to the torque converter and the torque converter inlet relief valve. The torque converter inlet relief valve limits the oil pressure to the torque converter. When oil pressure to the torque converter exceeds 900 ± 70 kPa (130 ± 10 psi), the inlet relief valve opens and sends the excess oil pressure to drain.
6 Modulating Valve FIRST SPEED Torque Converter Inlet Relief Valve Filter Transmission Pump Tank Main Relief Valve
Torque Converter Power Train ECM 4 5 5 Modulating Valve SECOND SPEED 3 3 Modulating Valve 1 Torque Converter Outlet Relief Valve
To Transmission Bearing Lubrication Modulating Valve 1 Screen Group Magnet 2 2 Modulating Valve FORWARD REVERSE FOURTH SPEED 6 6 4 Modulating Valve THIRD SPEED Cooler
Oil in the torque converter flows out of the torque converter through the torque converter outlet relief valve. The outlet relief valve maintains the pressure in the torque converter at a
minimum of 415 ± 135 kPa (60 ± 20 psi) at torque converter stall rpm.
From the torque converter outlet relief valve, the oil flows through the transmission oil cooler and then to the transmission for cooling and lubrication of the bearings and planetary.
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This illustration shows the transmission hydraulic system with the engine running and the transmission shift lever in the REVERSE position and the speed selector in SECOND SPEED. When the engine is running, flow from the pump is sent through the filter to the six
transmission solenoid valves. Pump flow is also sent to the transmission relief valve. The transmission relief valve limits the transmission oil pressure to the modulating valves. When SECOND SPEED REVERSE is selected, the Power Train ECM energizes the No. 1 solenoid and the No. 5 solenoid. The modulating valve controls the flow of oil to the No. 1 and No. 5 clutches.
When the No. 1 and No. 5 solenoids are energized, the electromagnetic force moves the
armature against the ball. The ball moves to the right against the seat. The oil flow through the center of the valve spool is blocked. The oil pressure increases at the left end of the valve spool and the valve spool moves to the right against the spring. Then, oil flow is directed to the ports for clutch 1 and clutch 5.
From the main relief valve, oil flows to the torque converter and the torque converter inlet relief valve. The torque converter inlet relief valve limits the oil pressure to the torque converter. When oil pressure to the torque converter exceeds 900 ± 70 kPa (130 ± 10 psi), the inlet relief valve opens and sends the excess oil pressure to drain.
6 Modulating Valve FIRST SPEED Torque Converter Inlet Relief Valve Filter Transmission Pump Tank Main Relief Valve
Torque Converter Power Train ECM 4 5 5 Modulating Valve SECOND SPEED 3 3 Modulating Valve 1 Torque Converter Outlet Relief Valve
To Transmission Bearing Lubrication Modulating Valve 2 REVERSE Screen Group Magnet 1 Modulating Valve FORWARD 2 FOURTH SPEED 6 6 4 Modulating Valve THIRD SPEED Cooler
Oil in the torque converter flows out of the torque converter through the torque converter outlet relief valve. The outlet relief valve maintains the pressure in the torque converter at a
minimum of 415 ± 135 kPa (60 ± 20 psi) at torque converter stall rpm.
From the torque converter outlet relief valve, the oil flows through the transmission oil cooler and then to the transmission for cooling and lubrication of the bearings and planetary.
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Transmission Modulating Valve - No Commanded Signal
In this illustration, the transmission modulating valve is shown with no current signal applied to the solenoid. The Transmission ECM controls the rate of oil flow through the transmission modulating valves to the clutches by changing the signal current strength to the solenoid. With no current signal applied to the solenoid, the transmission modulating valve is DE-
ENERGIZED and oil flow to the clutch is blocked. The transmission modulating valve is located on the transmission control valve.
Pump oil flows into the valve body around the valve spool and into a drilled passage in the center of the valve spool. The oil flows through the drilled passage and orifice to the left side of the valve spool to a drain orifice. Since there is no force acting on the pin assembly to hold the ball against the drain orifice, the oil flows through the spool and the drain orifice past the ball to the tank.
The spring located on the right side of the spool in this view holds the valve spool to the left. The valve spool opens the passage between the clutch passage and the tank passage and blocks the passage between the clutch passage and the pump supply port. Oil flow to the clutch is blocked. Oil from the clutch drains to the tank preventing clutch engagement.
From Pump Test Port Ball Valve Spool Spring Drain Orifice Solenoid Pin To Tank To Clutch Orifice