GMC 4000 Series Service Manual page 450

RETARDER ADJUSTMENT
The transmission retarder (when used) on
vehicles covered by this manual is actuated by
either hydraulic or mechanical type controls.
Adjustment for each system
follows:
Hydraulic Controls - Tilt Cab Models
(Refer to Fig. 7)
NOTE: Adjustment
with the exception of the slave cylinder is the
same as hydraulic adjustment as covered in
"CLUTCH CONTROLS" (SEC. 7D) in this manual.
Be sure to adjust the master cylinder push rod
prior to adjustment of the slave cylinder.
A djust sla v e cy lin d er a s follow s:
1. Disconnect slave cylinder return spring
from lever (C).
2. Disconnect clevis (F) from lever (C).
3. Insert 1/4-inch diameter pin (D) through
hole (C) and into alignment hole in cylinder
bracket (B).
4. Loosen nut (G) and adjust clevis (F) for
free-entry of clevis pin into lever (C). Tighten
nut (G) and retain clevis pin in place with cotter
pin.
5. Connect slave cylinder return spring to
lever (C).
6. Remove 1/4-inch diameter pin from lever
(C).
Mechanical Controls - " E" and " S;'
Models (Refer to Fig. 8)
NOTE: On some
swivel on the push rod is located at the idler
lever, instead of the retarder lever, as shown.
When the adjustment swivel is located idler lever
the following procedure is
replacing retarder lever with idler lever.
1. Loosen nuts " A" and " B" .
2. Remove clip retaining swivel to retarder
lever, then remove swivel from retarder lever.
3. With retarder pedal against stop bumper
(in cab), adjust swivel on push rod for free-entry
into retarder lever.
4. Tighten nuts " A" and " B" to retain swivel
in position. Install clip to retain swivel to re­
tarder lever.
NOTE: Referring to Inset, figure 5, the
retarder valve is shown in the " OFF" position.
Full travel of valve from " OFF" to "ON" posi­
tion is 1/2-inch.
5. Have an assistant depress retarder pedal
G M C S E R V I C E M A N U A L
is described as
of hydraulic controls,
models the adjustment
simply revised by
TRANSMISSION CONTROL LINKAGE
(in cab), while checking for proper movement of
retarder valve. Use a scale to be sure move­
ment of valve from " OFF" to " ON" position is
1/2-inch.
6. Have assistant release retarder pedal.
The retarder valve must return to the " OFF"
position (retarder valve fully closed) when the
pedal is released. The pedal must return posi­
tively and immediately to released position (pedal
against bumper stop) when foot pressure is
released.
7. Readjust linkage, if necessary.
Sec. 7A
Page 439