not have to select ranges. A "break torque" fea-
ture allows the driver to move the shift lever and
take the transmission out of gear without chang-
ing throttle position. Throttle position can be
maintained while braking and downshifting
through the gears when stopping the vehicle, as
well as on steep grades.
The major components of the ESS system are
the system switch, shift-intent switch, input and
output shaft speed sensors, a Neutral position
sensor, and an electro-pneumatic solenoid.
Operation, ESS
The ESS system collects and relays information per-
taining to the positions of the shift-intent and system
switches (
Fig. 8.29
), transmission input and output
shaft speeds, and shift lever position. The informa-
tion is received by the engine Electronic Control
Module (ECM) which signals the fuel control system
to increase or decrease engine rpm to match road
speed. The ECM also controls HI and LO range se-
lection in the auxiliary case on the rear of the
transmission.
The system switch (
Fig. 8.29
) is the lower switch lo-
cated on the driver’s side of the shift handle. It con-
trols ESS system operation. When in the down posi-
tion, the system is operating and the word ON is
visible on the switch. In the up position, the word
OFF is visible, the system is not operating, and the
transmission can be shifted manually.
The shift-intent switch (
Fig. 8.29
) is the upper switch
on the driver’s side of the shift handle. It has four
positions and controls upshifting and downshifting by
communicating to the ECM the driver’s intention of
changing gears.
NOTE: If the system switch is OFF, use the
shift-intent switch to select between ranges.
Push the top of the switch (
Fig. 8.30
) to select
the HI range on upshifts and the bottom of the
switch (
Fig. 8.31
) to select the LO range on
downshifts.
WARNING
Make sure that the transmission is in neutral (N)
when you start the vehicle. If the vehicle is
started in gear, it will suddenly move forward or
backward which could result in personal injury
and damage to property and the transmission.
02/17/98
f270058
1
2
1.
Shift-Intent Switch
2.
System Switch
Fig. 8.29, ESS Shift Handle
02/17/98
f270059
A
B
A. Press the top portion (engage the first position) of
the shift-intent switch to begin an upshift.
B. Press the top portion again (engage the second
position) to break torque.
Fig. 8.30, ESS Upshifting Using the Shift-Intent Switch
02/17/98
A
B
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A. Press the bottom portion (engage the first position)
of the shift-intent switch to begin a downshift.
B. Press the bottom portion again (engage the second
position) to break torque.
Fig. 8.31, ESS Downshifting Using the Shift-Intent
Switch
Transmissions
8.33
