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TM 10-3930-671-24
8.1. Service Brake & Inching Systems
Description and Operation................................................. F-383
Parking Brake Linkage ...................................................... F-384
This section reviews the arrangements of brake and
inching systems and components used in GPX25 E
truck.
Description and Operation
The GPX25 E has a manual (not powered) hydraulic
service brake system, with dual suspended foot pedals
which are connected to dual individual master cylinders*.
The master cylinder applies pressure through the brake
lines to the brake (wheel) cylinders located in either
brakes at the wheels
*See Section 2.0, Product Specification Changes.
The GPX25 E incorporates a hydraulic inching system in
combination with the service brake system master
cylinder and pedal arrangement, as described later. In all
cases, the left-hand pedal is intended for inching use and
the right-hand foot pedal is provided for normal braking
control of the truck.
Type 2 Dual Master Cylinders
Type:
Dual (2) master cylinders with
separate circuits for inching and
braking.
Arrangement:
Brake
master
cylinders
(2)
mounted
in
vertical
position
under
dash
and
connected
directly
to
individual
brake
pedals.
Separate
remote-
mounted reservoir mounted in
upper left corner of dash.
Effective Date:
Mid 1989 Lot 7158 and above
Transaxle Model.
TA18
With Type 2 dual master cylinder system, the right-hand
pedal is separate and used for braking only. The right-
hand pedal and cylinder operate the brake system and
the left-hand pedal and cylinder operate the inching
system. Left-hand pedal actuates right-hand pedal to
provide braking also. See inching operation below.
TA1 8 Transaxle
Type 2 Dual Master Cylinders Only
Master cylinders, reservoir and lines form a closed circuit
using conventional 5A E/ Type DOT 3 automotive
hydraulic brake fluid.
Brake and inching master cylinders are mounted
vertically side-by-side under dash and connected directly
to foot pedals. Master cylinders are single-action type
with no residual check valve. Separate remote-mounted
reservoir is installed in upper left corner of dash. Master
cylinders are equipped with seals for use with hydraulic
brake fluid only.
Service brakes are hydraulically-actuated, self-adjusting
drum-and-shoe brakes at the drive wheels. Service
brake assemblies are part of the transaxle assembly,
and are mechanically-actuated for parking.
Inching Control System
Control of the inching function is provided by a combined
"left foot inching and braking" action. The first part of the
pedal motion moves the transmission control valve to
regulate release of the driving clutch pressure, which
allows the clutch to slip and produce only the driving
force and speed desired.
The last part of the pedal motion releases the clutch
entirely and applies the service brakes.
With Type 2 dual master cylinder system, hydraulic
inching is incorporated into only the left-hand pedal. Left-
hand pedal actuates right-hand pedal to provide braking
also. Right-hand pedal is separate and used for braking
only with TA18 transaxle.
F-383
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