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| Illustration 1 | g00666212 |
Transmission Hydraulic Control (1) Transmission hydraulic control relief valve. (2) Transmission clutch modulating valves. (3) Torque converter inlet relief valve. | |
The transmission hydraulic control controls the oil pressure to the torque converter, to the transmission clutches, and to the lubrication circuits. The transmission hydraulic control also controls the flow of oil to the clutches. The transmission hydraulic control is installed on the top of the transmission planetary group and on the side of the torque converter housing. The transmission hydraulic control consists of the following components: transmission hydraulic control relief valve (1), six transmission clutch modulating valves (2) and torque converter inlet relief valve (3) .
Pressurized oil for the operation of the transmission hydraulic control flows from the transmission oil pump to the transmission oil filter. The oil flows through a hose to the oil inlet in the torque converter housing. The oil flows through internal passages in the torque converter housing in order to supply transmission hydraulic control relief valve (1) with oil. The oil also flows through internal passages in the transmission housing in order to supply the six transmission clutch modulating valves (2) with oil.
The six transmission clutch modulating valves (2) are mounted on the top of the transmission under the cab. The six transmission clutches have an individual transmission clutch modulating valve (2). In order to move the machine, a direction clutch solenoid and a speed clutch solenoid must be energized. The transmission clutch modulating valves (2) are used to directly modulate the oil pressure that is sent to each individual clutch.
The following table provides the combination of the energized solenoids and engaged clutches for each forward speed and for each reverse speed.
| Speed Range and Direction | Clutches and Solenoids that are Engaged |
| Fourth Speed Forward | 3 and 2 |
| Third Speed Forward | 4 and 2 |
| Second Speed Forward | 5 and 2 |
| First Speed Forward | 6 and 2 |
| Neutral | 3 |
| First Speed Reverse | 6 and 1 |
| Second Speed Reverse | 5 and 1 |
| Third Speed Reverse | 4 and 1 |
| Fourth Speed Reverse | 3 and 1 |
Transmission hydraulic control relief valve (1) controls the pressure of the oil that is supplied to transmission clutch modulating valves (2). The oil pressure overcomes the spring force of the transmission hydraulic control relief valve. Torque converter inlet P3 oil then flows to the torque converter.
Torque converter inlet relief valve (3) limits P3 torque converter inlet oil pressure to a maximum of 900 ± 70 kPa (130 ± 10 psi). Torque converter inlet relief valve (3) is located in the torque converter housing. Transmission hydraulic control relief valve (1) is located above torque converter inlet relief valve (3). Transmission hydraulic control relief valve (1) must be removed in order to attain access to the torque converter inlet relief valve (3) .
Reference: For additional information on the operation of the transmission clutch modulating valves, refer to the Service Manual module for Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.