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| Illustration 1 | g01247758 |
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Transmission Control (1) Number 1 clutch modulating valve (2) Number 2 clutch modulating valve (3) Number 3 clutch modulating valve (4) Number 4 clutch modulating valve (5) Number 5 clutch modulating valve (6) Number 6 clutch modulating valve (7) Number 7 clutch modulating valve (8) Transmission hydraulic control relief valve (9) Transmission lubrication relief valve | |
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| Illustration 2 | g06078756 |
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Torque converter 777E series truck (10) Modulating valves (transmission clutch) (11) Torque converter inlet relief valve (12) Torque converter outlet relief valve | |
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| Illustration 3 | g01248184 |
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Torque converter 777F series truck (10) Modulating valves (transmission clutch) (11) Torque converter inlet relief valve (12) Torque converter outlet 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: relief valve for the transmission hydraulic control (8), seven modulating valves (1) through modulating valve (7), torque converter inlet relief valve (11) and torque converter outlet relief valve (12).
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 to supply transmission hydraulic control relief valve (8) with oil. The oil also flows through internal passages in the transmission housing to supply the seven modulating valves with oil.
The seven modulating valves are mounted on the top of the transmission. The seven transmission clutches have an individual modulating valve. To move the machine, two clutch solenoids must be energized. The modulating valves 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 reverse.
| Assignments for the Transmission Clutch | |||||||
| Gear | Clutches | ||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | |
| Neutral | X | ||||||
| Reverse | X | X | |||||
| First | X | X | |||||
| Second | X | X | |||||
| Third | X | X | |||||
| Fourth | X | X | |||||
| Fifth | X | X | |||||
| Sixth | X | X | |||||
| Seventh | X | X | |||||
Transmission hydraulic control relief valve (8) controls the pressure of the oil that is supplied to modulating valves . The oil pressure overcomes the spring force of the transmission hydraulic control relief valve.
Reference: For additional information on the operation of the modulating valves, refer to the Service Manual module for Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.