TM 5-3805-291-23-1
THEORY OF OPERATION - CONTINUED
0003 00
POWERTRAIN - CONTINUED
a.
General.
(1)
Transmission hydraulic control controls oil pressure to torque converter, transmission clutches, and lubri-
cation circuits, as well as controlling oil flow to clutches. Transmission hydraulic control is installed on
top of transmission planetary group and on side of torque converter housing. Transmission hydraulic con-
trol consists of these components: transmission hydraulic control relief valve, six modulating valves,
torque converter inlet relief valve, and torque converter outlet relief valve.
(2)
Pressurized oil for transmission hydraulic control operation flows from transmission oil pump to transmis-
sion oil filter, then through a hose to torque converter housing oil inlet. Oil flows through internal passages
in torque converter housing to supply transmission hydraulic control relief valve with oil. Oil also flows
through internal passages in transmission housing to supply six modulating valves with oil.
(3)
Six modulating valves are mounted on top of transmission under cab. Six transmission clutches have an
individual modulating valve. To move machine, a direction clutch solenoid and a speed clutch solenoid
must be energized. Modulating valves are used to directly modulate oil pressure sent to each individual
clutch.
(4)
Table 5 provides combinations of energized solenoids and engaged clutches for each forward and reverse
speed.
Table 5. Solenoid/Clutch Combinations.
Engaged Clutches and
Speed Range and Direction
Energized Solenoids
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
(5)
Transmission hydraulic control relief valve controls oil pressure supplied to modulating valves. Oil pres-
sure overcomes spring force of transmission hydraulic control relief valve. Torque converter inlet P3 oil
then flows to torque converter.
(6)
Torque converter inlet relief valve limits P3 torque converter inlet oil pressure to a maximum of 130 10
psi (900 70 kPa). Torque converter inlet relief valve is located in torque converter housing. Transmission
hydraulic control relief valve is located above torque converter inlet relief valve and must be removed to
access torque converter inlet relief valve.
0003 00-50
