TM 5-3805-290-23-1
THEORY OF OPERATION - CONTINUED
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TRANSMISSION - CONTINUED
a.
Relays. There are three system relays activated directly by machine ECM: ride control, parking brake alarm relay,
and backup alarm relay.
(1)
Ride Control. Machine ECM activates ride control when ride control/load check switch is placed in ON
position. Activation is based on machine ground speed in AUTO position. Ride control system diminishes
effects of a loaded bucket when machine moves at higher speeds.
Backup Alarm Relay. Backup alarm relay is used to activate backup alarm when transmission is placed in
(2)
REVERSE position.
b.
Modulating Valves.
N OT E
Solenoid coils are not designed to be operated at 24 DCV directly. Machine ECM sends a 24 volt Pulse
Width Modulated (PWM) signal at a duty cycle which provides an average voltage of about 12 volts to sole-
noid coils. DO NOT energize solenoid coils with 24 DCV (+battery). Life of solenoid coils will be drastically
reduced if solenoid coils are energized with 24 DCV (+battery). If solenoid coils must be energized by a
source that is different from machine ECM, use 12 DCV to energize solenoid coils.
(1)
Modulating valves are located on right side of machine on top of transmission.
(2)
Two solenoids must be activated to move machine. One solenoid is for direction and one solenoid is for
speed. When solenoid is activated, it receives a signal from machine ECM. Each modulating valve is con-
trolled by a solenoid. Solenoids are controlled by machine (ECM). Modulating valves are used by machine
ECM to directly modulate oil pressure sent to each individual clutch. When operator selects a direction
and speed, machine ECM sends a PWM signal to vary current to solenoid on modulating valve. Amount of
current sent to solenoid regulates amount of oil pressure supplied to selected clutch. When machine ECM
sends maximum current to solenoid, oil pressure in clutch is at maximum. When no current is sent to mod-
ulating valve, oil pressure in clutch is at minimum.
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