SECOND SPEED FORWARD

3516B HD ENGINE DERATES

CONVERTER DRIVE

Oil to Water Cooler

Air to Water Cooler

Air to Water Cooler Lube - Rear Pump Drive Transmission Lube Dump Orifice Lube - Output Transfer Bearings Lube - Output Transfer Gear Magnetic Screens P3 Lube - Input Transfer SOS SOS 2 5 Transmission Control Valve P2 P1 4 1 3

When the transmission is shifted from First Speed Forward to Second Speed Reverse (directional shift), the Power Train ECM de-energizes clutch solenoids No. 2 and 5 and energizes clutch solenoids No. 1 and 4. The ECM also energizes the impeller clutch solenoid and de-energizes the lockup clutch solenoid.

When the Power Train ECM de-energizes the No. 2 clutch solenoid, the No. 2 clutch solenoid valve blocks the pilot oil flow and sends the pilot oil at the end of the selector spool to drain. The force of the selector valve spring moves the spool to its center position. When the selector spool moves to the center position, oil in the No. 2 clutch flows to the sump.

When the Power Train ECM energizes the No.1 clutch solenoid, the No. 1 clutch solenoid valve sends pilot oil to the lower end of the directional selector spool. The force of the oil pressure overcomes the force of the selector valve spring and shifts the spool from its center position. Directional clutch oil flows from the pressure differential valve, past the directional selector spool, and into the REVERSE clutch (No. 1).

Torque Converter Pump Drive Transmission Pump Sump Transmission Filter Torque Converter Filter Priority Valve Impeller Clutch Modulating Valve Lockup Clutch Modulating Valve

Oil to Water Cooler

Air to Water Cooler

Air to Water Cooler Lube - Rear Pump Drive Dump Orifice Transfer Bearings Transfer Gear Magnetic Screens Lube - Input Transfer SOS SOS 3 1 2 5 2 3 1 5 4 4 Transmission Control Valve P2 P3 P1

When the Power Train ECM de-energizes the No. 5 clutch solenoid, the No. 5 clutch solenoid valve blocks the flow of pilot oil and sends the pilot oil at the end of the 1st and 3rd selector spool to the sump. The selector spool moves to the center position, oil in the No. 5 clutch flows to the sump.

When the ECM energizes the No. 4 clutch solenoid, the No. 4 clutch solenoid valve sends pilot oil to the right side of the 2nd speed selector spool. The force of the oil pressure overcomes the force of the selector spool spring and moves the spool from its center position. Oil from the inlet passage flows through the orifice, past the 1st and 3rd speed selector spool, past the 2nd speed selector spool, and into the No. 4 speed clutch.

As the empty No. 1 and 4 clutches fill, they cause the P1 and P2 pressures to decrease to less than 375 kPa (55 psi) momentarily. The momentary decrease in P1 oil pressure allows the differential valve spring to move the differential valve up. When the differential valve moves up, the differential valve opens a passage for oil in the differential valve spring chamber and the load piston cavity to flow to drain. The transmission control valve then repeats the fill and modulation cycle.

During a directional shift, the Power Train ECM reduces the pressure in the impeller clutch allowing the impeller clutch to slip. The ECM monitors the torque converter output speed sensor and the transmission output speed sensor to determine when the transmission clutches are engaged. When the transmission clutches are engaged, the ECM engages the impeller clutch in the torque converter. The torque converter absorbs the energy of a directional shift.

When the machine is operating in torque converter drive, six conditions must be present before the Power Train ECM will energize the solenoid for the lockup clutch and shift the torque converter to direct drive.

1. The transmission is in second or third gear.

2. The lockup clutch enable switch is in the ON position. 3. The torque converter output speed is above 1375 ± 5rpm.

4. The machine has been in the present speed and direction for more than two seconds. 5. Neither brake pedal is depressed.

6. The lockup clutch has been released by the Power Train ECM for at least four seconds.

Oil to Water Cooler

Air to Water Cooler

Air to Water Cooler Lube - Rear Pump Drive Dump Orifice Transfer Bearings Transfer Gear Magnetic Screens Lube - Input Transfer SOS SOS 3 2 5 2 3 1 5 4 4 Transmission Control Valve P2 P3 P1 1

When the solenoid for the lockup is energized, the lockup clutch modulating valve opens. The transmission pump oil flows past the lockup clutch modulating valve and fills the lockup clutch. The lockup clutch engages and connects the turbine to the rotating housing.

In DIRECT DRIVE, both the impeller clutch and the lockup clutch are engaged. The torque converter rotating housing, the impeller, and the turbine turn as a unit.

This illustration is a sectional view that is showing the transmission planetary group. The planetary group is equipped with two directional and three speed clutches.

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

Speed Engaged Clutches

First/Forward No. 2 and No. 5 Second/Forward No. 2 and No. 4 Third/Forward No. 2 and No. 3

Neutral No. 3

First/Reverse No. 1 and No. 5 Second/Reverse No. 1 and No. 4 Third/Reverse No. 1 and No. 3

Planetary Carrier Input Sun Gears

Ring Gears

Input Shaft

Output Shaft

Output Sun Gears Ring Gear

1 2 3 4

The 994F Wheel Loader is equipped with two oil-to-coolant coolers (1) and two oil-to-air coolers (2) and (3). The oil-to-coolant coolers are located on the left side of the engine. These two coolers use engine coolant to cool the transmission oil as the oil passes through the coolers. In line with the transmission oil flow through the two oil-to-coolant, an orifice is installed to divide the flow of oil between the oil-to-coolant and two oil-to-air coolers. Approximately two thirds of the torque converter outlet oil flows through the oil-to-coolant coolers.

The two oil-to-air coolers are located in the cooler package at the rear of the machine.

Cooler (3) has an orifice (4) that divides the other one-third of the transmission oil in half. One half of the oil flows through cooler (2) and one half of the torque converter oil flows through cooler (3). The oil from the coolers flows back to the transmission and lubricates the

transmission bearings before returning to the transmission sump. A second orifice (5) is installed in a junction block that is attached to the frame of the machine.

3 ₄

The upper illustration shows the orifice (1) in the smaller of the two coolers. The orifice restricts the flow through the smaller cooler in order to equally divide the flow between both coolers.

The lower illustration shows the orifice (2) in the block that is attached to the rear frame (3). Access the block with the orifice from below the machine. The orifice is installed in the block to restrict the flow to approximately one-third of the flow of oil through the air-to-oil coolers.

79 1

In document Manual nuevo (Page 90-98)