777F Off-Highway Truck Power Train: Check Valve (Transmission Oil Cooler Inlet), Oil Cooler (Transmission) & Transmission Hydraulic Control

1.-Check Valve (Transmission Oil Cooler Inlet)

(1) Transmission scavenge section of the gear pump for the power train (2) Transmission oil cooler(3) Bypass check valve for the transmission cooler

The transmission scavenge section of the gear pump (1) pulls oil from the sump of the transmission. The oil is sent to transmission oil cooler (2) in order to be cooled by the engine's jacket water. The cooled oil is then returned to the transmission section of the hydraulic tank.

If the transmission oil is cold or if the core of the transmission oil cooler (2) becomes plugged, the oil pressure may become too high. When the pressure exceeds 448 kPa (65 psi) a ball unseats in the bypass check valve for the transmission cooler (3) and the transmission oil bypasses the transmission oil cooler. When the transmission oil cooler is in the bypass mode, the oil returns directly to the transmission section of the hydraulic tank.

2.-Oil Cooler (Transmission)

(1) Transmission oil cooler

Transmission oil cooler (1) is located on the frame to the right side of the engine. Engine coolant goes through transmission oil cooler (1) in order to cool the oil. The transmission scavenge pump pulls oil from the transmission sump. The transmission scavenge pump sends the oil to the transmission oil cooler. The oil will flow from transmission oil cooler (1) to the transmission section of the hydraulic tank.

3.-Transmission Hydraulic Control

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

Torque converter (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 in order to supply transmission hydraulic control relief valve (8) with oil. The oil also flows through internal passages in the transmission housing in order 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. In order 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.

Table 1

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.

ReferenceFor 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.

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777F Off-Highway Truck Power Train: Check Valve (Transmission Oil Cooler Inlet), Oil Cooler (Transmission) & Transmission Hydraulic Control 2013-01-04T15:53:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown