Diagram and Real Location of Power Shift Transmission Caterpillar D9R

The D9R transmission is located at the rear of the machine for easy removal and installation. The three-speed forward, three-speed reverse planetary power shift transmission transfers power from the engine to the final drives. The transmission contains three hydraulically controlled speed clutches and two hydraulically controlled directional clutches. The operator manually selects the direction and speed range. With a transmission speed and directional clutch ENGAGED, the transmission sends power to the pinion and bevel gear, the steering clutches and brakes (non-differential steer machines), and the final drives. Differential steer machines are equipped with an additional drive input and planetary gear set for steering which replace the steering clutches.

power shift compponent location

The speed clutch pressure (P1) test port (1), and the directional clutch pressure (P2) test port (2) are located on the rear of the transmission housing. The plugs are removed and replaced with test fittings to measure the P1 and P2 pressures. The torque converter inlet pressure tap (3) and the transmission lube pressure tap (4) are also located on the rear of the transmission housing.

power shift compponent location 2

Shown here is a sectional view of the transmission group. The planetary group has two directional and three speed clutches which are numbered in sequence (1 through 5) from the rear of the transmission to the front.

Clutches No. 1 and 2 are the reverse and forward directional clutches. Clutches No. 3, 4, and 5 are the third, second, and first speed clutches. The No. 5 clutch is a rotating clutch.

In this sectional view of the transmission, the input shaft and input sun gears are shown in red. The output shaft and output sun gears are blue. The ring gears are shown in green. The planetary carriers are brown. The planet gears and shafts are shown in orange. The clutch discs, clutch plates, pistons, springs, and bearings are shown in yellow. The stationary clutch housings are shown in gray.

The input sun gears are splined to the input shaft and drive the directional gear trains. The output shaft is driven by sun gears No. 3 and 4 and rotating clutch No. 5. When the No. 2, 3, or 4 clutches are engaged, their respective ring gears are held stationary. The No. 1 planetary carrier is held when the No. 1 clutch is engaged. When engaged, the No. 5 rotating clutch locks the output components (for FIRST gear) to the output shaft.

power shift compponent location 3

The power train oil dipstick (1) and fill tube (2) are located below a hinged cover on the left side of the machine. Also located in this compartment are the machine disconnect switch (3) and the oil fill cap (4) for the pivot shaft compartment.

Comparison of Component Locations for Different Caterpillar D9R Version

That illustration shows a comparison of component locations for both the differential steer version and the steering clutch and brake version of the D9R. Component layouts for the two systems are very similar except for the following items:

  • Steering pump on the differential steer machine
  • Four-section PTO pump on the clutch and brake machine compared to the three-section PTO pump and torque converter scavenge pump on the differential steer machine
  • Differential steer planetaries are located in the transmission housing on the differential steer machine
  • Steering motor for turning on the differential steer machine
  • Clutch and brake packs on the clutch and brake machine compared to the service brake packs on the differential steer machine.

Hydraulic and Mechanical Torque Divider Functions in Torque Converter

The D9R Track-type Tractor uses a torque divider (arrow) to transfer engine power to the transmission. The torque divider in this view is mounted to a 3408 engine. The torque divider is similar to those used on other Caterpillar track-type tractors except the D9R torque divider is also equipped with a freewheel stator.

The torque divider provides both a hydraulic and a mechanical connection from the engine to the transmission. The torque converter provides the hydraulic connection, while the planetary gear set provides the mechanical connection. During operation, the planetary gear set and the torque converter work together to provide an increase in torque as the load on the machine increases.

torque devider 2

This illustration shows the torque divider that is used in both versions of the D9R. The impeller, rotating housing, and sun gear are shown in red. These components are on a direct mechanical connection to the engine flywheel (also shown in red). The turbine and the ring gear, shown in blue, are connected. The planetary carrier and output shaft, shown in purple, are also connected. The stator and carrier are shown in green.

The planetary gears and shafts are orange. Bearings and the lockup mechanism for the stator are shown in yellow.

Because the sun gear and the impeller are connected to the flywheel, they will always rotate at engine speed. As the impeller rotates, it directs oil against the turbine blades, causing the turbine to rotate. Turbine rotation causes the ring gear to rotate. During NO LOAD conditions, the components of the planetary gear set rotate as a unit at the same rpm. The planet gears do not rotate on their shafts.

As the operator loads the machine, the output shaft slows down. A decrease in output shaft speed causes the rpm of the planetary carrier to decrease. Decreasing the planetary carrier rotation causes the relative motion between the sun gear and the planet carrier to cause the planet gears to rotate. Rotating the planet gears decreases the rpm of the ring gear and the turbine. At this point, the torque converter multiplies torque and the planetary gear set splits the torque.

An extremely heavy load can stall the machine. If the machine stalls, the output shaft and the planetary carrier will not rotate. This condition causes the ring gear and turbine to slowly rotate in the opposite direction of engine rotation. Maximum torque multiplication is achieved just as the ring gear and turbine begin to turn in the opposite direction.

The torque divider is also equipped with a freewheel stator. The stator is splined to a cam which rotates around the stationary carrier in only one direction. Machined into the cam are tapered openings which contain rollers and springs. Spring force holds the rollers against the taper and carrier and restricts the cam from turning.

When the machine is under a load, and the impeller and turbine are rotating at different speeds, the stator is held stationary because the rollers are wedged in the taper of the openings by spring force. This mechanical connection keeps the stator stationary and allows oil flow to be directed back to the impeller and multiply the torque.

During all load conditions, the torque converter provides 75% of the output, and the planetary gear set provides the remaining 25% of the output. The size of the planetary gears establishes the torque split between the hydraulic torque and the mechanical torque.

When the machine speed increases with no load, the speed of the turbine and impeller increases. During this condition the stator does not need to redirect oil back to the impeller. The stator begins to turn in the same direction as the impeller and turbine and moves the rollers from the tapered openings against the spring pressure. The mechanical connection between the cam and the stationary carrier is broken. The stator, turning freely with the turbine and impeller, will reduce turbulence of the oil in the torque converter. The lack of turbulence in the torque converter permits the engine to work easier to reduce fuel consumption and minimizes heat build-up in the power train oil system.

See Monitor Panel Caterpillar D9R

The instrument panel (through Machine Serial No. 7TL1-851 and 8BL1-1052) includes the Computerized Monitoring System (CMS) display used for monitoring the machine systems. The instrument panel also includes the individual system switches, action light, a key start switch, action horn (not visible), service hourmeter, a vacuum fluorescent display panel, and system fuses and circuit breakers. In the upper left corner of the panel are the switches for various machine functions. The first four switches activate machine lighting. The next switch to the right is used for auxiliary electrical power. The final switch is used for ether injection to aid in starting the machine.

Cat Monitoring System D9R

The instrument panel (on Machine Serial No. 7TL852-Up, 8BL1053-Up, ABK 1-Up, and ACL 1-Up) includes the Caterpillar Monitoring System.

The Caterpillar Monitoring System continuously monitors machine systems. The system is a flexible, modular monitoring system that includes: a main display module (1), gauge cluster module (2), speedometer/tachometer module (3), various switches and sensors, an action lamp (4) and action alarm.

About Fuel Tank Caterpillar D9R

The D9R fuel tank is located on the rear of the machine behind the operator’s station. A strainer in the fuel fill tube keeps debris out of the fuel tank during refueling. A vented cap prevents pressure build-up in the fuel tank and also prevents cooling fuel from creating a vacuum. The fuel tank has been designed with an indentation in the top center to improve the operator’s view for rear attachment operations. The capacity of the tank for the earlier D9R (7TL and 8BL) is approximately 818 L (216 gal.).

The capacity of the tank for the later D9R (ACL and ABK) has been increased by 10% to 930 L (240 gal.).

fast fill connector

Some machines are equipped with a fast fill connector (arrow) for refueling the tank. This attachment allows fuel to be pumped into the tank under pressure for quicker refueling and shorter downtime while refueling.

Introducing Radiator D9R Caterpillar

The D9R is equipped with an Advanced Modular Core System (AMOCS) radiator. The AMOCS has two major advantages over earlier designs.

The first advantage is the improvement of the modular core servicablilty. The AMOCS radiator has been designed to include one divided tank below the modular cores. This design eliminates the tank which was formerly attached to the top of the modular cores. By locating both tanks below the modular cores, removal of a singular modular core is simplified. By eliminating the top tank, the seals for all the modules need not be disturbed if only one must be replaced. The maintenance time to replace a single module is considerably reduced. The second advantage of the AMOCS is a higher cooling performance. The modular cores are “two-pass” since both tanks are located below the cores. “Two-pass” means that the fluid from one tank is sent up one tube in the core and sent down the other side of the same core to the adjacent tank. This feature allows the fluid to make two cooling passes through the modular cores, thereby improving cooling performance.

The cooling system on the later D9R (ACL and ABK) has been changed from the earlier D9R. A separate water pump has been added to the engine to provide lower temperature coolant through the aftercooler.

Cooler air is supplied to the engine, which provides improved efficiency and reduced emissions.

This design is referred to as a “Separate Circuit Aftercooler (SCAC)” system. The SCAC pump draws coolant from the left two cores of the AMOCS radiator. The temperature of this coolant is lower than in the other seven cores. The coolant in the two left cores is sent through the cores a second time. The coolant makes four cooling passes instead of two as in the remaining cores. The left cores are separated from the other cores by a baffle plate in the bottom tank. The baffle plate functions as an orifice, which allows some of the cooled jacket water from the engine to flow through the left cores and be recirculated. The SCAC pump then sends this coolant to the aftercooler.

The return coolant from the aftercooler goes through the front of the split bottom tank, then passes up and down the left cores to the left rear section of the split bottom tank. The SCAC pump draws coolant from this reservoir. This coolant then flows through the aftercooler to lower the temperature of the inlet air to the engine for more efficient combustion and reduced emissions.

Surge Tank D9R

The fill tube is located in the surge tank for the cooling system. The surge tank is located on the right side of the engine compartment. Access to the fill tube is provided by lifting a spring hinged door on top of the engine compartment. Correct coolant level can be checked two ways. A sight glass (arrow) in the surge tank is visible through a hole in the side of the engine compartment. The sight glass should always show fluid. If any   air can be seen in the sight glass, coolant needs to be added to the surge tank. A fluid level indicator is located inside the fill tube. The indicator should be submerged by the coolant in the surge tank. If this indicator is visible, fluid must be added to the surge tank. When adding coolant to the system, fill the surge tank to the bottom of the stand pipe in the neck of the fill tube.

HEUI system components (2)

coolant temperature sensor

The engine coolant temperature sensor (1) is located in the front of the right cylinder head. This sensor is used with the ECM to control various functions. The following systems or circuits use the temperature sensor output to the ECM:

  • The Caterpillar Monitoring System Coolant Temperature Gauge over the CAT Data Link
  • The High Coolant Temperature Warning Alert Indicator LED and Gauge on the Caterpillar Monitoring System panel. (The information is transmitted over the CAT Data Link.)
  • The Engine Demand Fan Control, if installed, uses the sensor signal reference to provide the appropriate fan speed.
  • The Cat Electronic Technician (ET) status screen coolant temperature indication.

The coolant flow switch (2) is mounted below the coolant temperature sensor at the inlet to the oil cooler. If the coolant flow stops, the switch will open, causing the coolant flow LED and the action lamp to flash and the action alarm will sound.

fan drive clutch

The 3408E Engine in the D9R is equipped with a variable speed fan drive clutch.

The fan control valve (1) and fan control valve solenoid (2) control fan speed.

The fan drive clutch uses the ECM and temperature sensor as the engine coolant temperature reference. If an electrical failure of the system occurs, the fan will go to maximum rpm.

The advantages of the system are:

  • Reduced fuel consumption in most conditions
  • Reduced engine overcooling at low ambient temperatures
  • Faster engine warm-up
  • More engine power available at the flywheel
  • Reduced noise

HEUI system components (1)

atmospheric pressure sensor

The atmospheric pressure sensor (1) is installed on the hydraulic supply pump group adapter and is vented to the atmosphere. A foam block below the sensor helps prevent the entry of dirt into the sensor. The sensor performs the following functions:

  • Ambient pressure measurement for automatic altitude compensation and automatic air filter compensation.
  • Absolute pressure measurement for the fuel ratio control, ET, Caterpillar Monitoring System panel (gauge) pressure calculations.

The fuel temperature sensor (2) is used for automatic fuel temperature compensation.

hydraulic pressure sensor

The hydraulic (injection actuation) pressure sensor (arrow) is located between the valve cover bases in the right fluid supply manifold.

The hydraulic pressure sensor is used to measure injector actuation hydraulic pressure for the ECM.

The ECM uses this pressure measurement to control the displacement of the hydraulic supply pump (through the pump control valve).

timing callibration

The timing calibration sensor (arrow) is installed in the flywheel housing.

This sensor (magnetic pickup) is installed in the hole normally reserved for the timing pin. (The pin is used to position the crankshaft with the No. 1 piston at top dead center.)

The timing calibration sensor is permanently mounted on the D9R because of accessibility.

turbo inlet pressure

The turbo inlet pressure sensor (arrow) is mounted between the air filter and the turbocharger.

This sensor is used in conjunction with the atmospheric pressure sensor to measure air filter restriction for engine protection purposes. The difference between the two pressure measurements is used as the filter differential pressure.

The engine ECM uses this calculation to determine whether derating is necessary to protect the engine.

turbo outlet pressure

At the front of the engine in the right cylinder head is the turbo outlet (boost) pressure sensor (arrow). This sensor is used with the ECM to control the air/fuel ratio electronically. This feature allows very precise smoke control, which was not possible with mechanically governed engines.

The sensor also allows boost pressure to be read using the service tools.

HEUI Hydraulic pump components

heui hydraulic pump component

The pump control valve (1), also referred to as the “injection actuation pressure control valve,” controls the angle of the pump swashplate which varies the pump oil flow. Also mounted on the hydraulic supply pump group is the hydraulic temperature sensor (2). This sensor is used by the ECM for viscosity compensation to maintain consistent fuel delivery and injector timing regardless of viscosity changes caused by varying hydraulic temperatures. Both sensors are threaded into the supply pump case.

heui hydraulic pump component 2

The oil pressure sensor (1) is mounted on the hydraulic pump. The oil pressure sensor is used by the ECM to generate a low pressure warning for the operator.

Also visible in this view are the hydraulic temperature sensor (2) and the pump control valve (3).

HEUI system components

heui system component

The principal component in the HEUI system, the Electronic Control Module (ECM, 1), is mounted on top of the right front valve cover. The ECM is the “heart” of the engine. The ECM performs engine governing, timing and fuel limiting. It also reads sensors and transmits data to the instrument display system through the CAT Data Link.

The hydraulic supply pump group (2) is mounted in the vee of the engine in the same position as the original fuel pump and governor for the 3408 engine. Flow from this pump supplies the actuating pressure for the injectors. The fuel transfer pump (not visible) is mounted on the rear of the hydraulic pump.

Also visible in this view is the primary speed/timing sensor (3). The primary speed/timing sensor is mounted to the timing gear housing on the right side of the engine. The secondary speed/timing sensor (not visible) is located on the other side of the timing gear housing.

The speed/timing sensors are used to calculate engine speed and crankshaft position for timing purposes. The sensors are self-adjusting, but special precautions are necessary during installation to prevent damage. The sensors maintain a zero clearance with the timing wheel.

secondary speed sensor

The secondary speed/timing sensor (arrow) is mounted to the timing gear housing on the left side of the engine.