TM 5-3810-307-24-1-1
AUTOMATIC POWERSHIFT CONTROL (APC 100)
DESCRIPTION
GENERAL
LOW CLUTCH PRESSURE WARNING
NOTE
The APC 100 monitors transmission clutch pressure.
If clutch pressure becomes critically low, the APC
The automatic powershift control is only
100 will cause the TRANS RPM/PRESS indicator to
applicable
to
the
carrier
cab.
light as a blinking warning, until normal clutch
Transmission control from the super-
pressure returns.
structure cab is manual.
OVERRIDE SYSTEM
The automatic powershift control (APC 100), located
behind the operator's seat, is a small computer
The override system allows the transmission to be
dedicated to transmission control. Information such
shifted manually. The override (automatic/manual)
as engine speed, turbine speed, gear selection, and
switch is mounted on top of the APC 100 mode
throttle position is used by the computer to determine
control fuse and relay box and energizes relays that
the proper time to shift the transmission. The APC
disconnect the shift solenoids from the computer and
100 prevents a dangerous shift if an improper gear is
connects them to the cab shift control. This allows a
selected with the shift control. Torque converter
vehicle disabled due to electronic shift failure to be
lockup is also controlled by the APC 100.
driven to the nearest maintenance point. Each time
the ignition switch is turned off and then back on, the
NOTE
override switch must be reset.
The safety
parameters set by the computer are not active in
Removing carrier cab seat will provide
system override.
easier access to the APC 100 and the
fuse and relay box.
INPUTS
DIRECT ENGAGEMENT PROTECTION
Automatic/Manual
From neutral, a forward or reverse gear cannot be
The automatic/manual mode (override) switch is on
selected if the engine speed is above 1000 rpm.
top of the APC 100 mode control fuse and relay box.
When changing direction, the engine speed must be
An open switch indicates automatic mode and a
less than 1000 rpm and the vehicle speed must be
closed switch indicates manual mode. A closed
less than one mph, or the transmission will shift into
switch inputs battery voltage. The manual mode
neutral.
must be reactivated each time the ignition switch is
turned off then back on.
If the crane is moving, drive can only be engaged
when the engine speed is less than 1200 rpm in 1st
Clutch Pressure
or 2nd, 1400 rpm in 3rd or 4th, and 1600 rpm in 5th
or 6th (both forward and reverse).
Clutch pressure is monitored by a clutch pressure
switch that closes if the clutch pressure becomes
DOWNSHIFT PROTECTION
critically low. A closed switch inputs battery voltage.
Downshifting is only allowed if there is no risk of
Engine Speed
overspeeding the transmission. If a gear is selected
that would result in an overspeeding condition, the
The engine speed input is obtained from a variable
computer will select the lowest gear that will not
reluctance speed sensor mounted in the converter
cause overspeeding and the TRANS RPM/PRESS
housing. The teeth of a ferrous target wheel pass by
indicator on the front console will be lit (steady). This
the pole of the sensor which produces a pulsed
condition will remain until the vehicle has slowed
signal. The APC 100 measures the time between
enough to make the shift into the selected gear.
the pulses to calculate the engine rpm.
