GMC 4000 Series Service Manual page 446

Cleaning and Inspection
1. Clean all metal parts thoroughly in clean­
ing solvent. Wipe or blow parts dry.
2. Check all parts f o r
cracks or other damage.
3. Replace all parts that would affect proper
selection of transmission gears.
Bushing Replacement
1. P ress or drive shift rail yoke bushing out
of bore in shift rail yoke (10, fig. 4).
2. Using a suitable sleeve, p ress or drive
new bushing into bore of shift yoke.
O il Seal R ep lacem en t
1. P ress or pry oil seal (11, fig. 4) out of re­
mote control cover.
2. Using a suitable sleeve, p ress or drive
new oil seal into bore of cover.
NOTE: Coat outer diameter of oil seal with
a coat of sealing cement prior to installation.
Assembly
NOTE: Key numbers
figure 4.
1. Coat all moving parts with transmission
TRUCK MODELS WITH ALLISON
LINKAGE ADJUSTMENTS
Prior to making any checks or adjustments
of transm ission manual and throttle control link­
age, check performance of the engine. The trans­
m ission is often blamed for poor operation of
the vehicle when the engine is not tuned to deliver
peak power. Refer to ENGINE (SEC. 6) in this
manual for recommended tune-up procedures. It
should be kept in mind, that to assure efficient
performance of power plant, the transmission
should be as carefully balanced with the engine
as are fuel and ignition system s.
The transmission control linkage must be
checked and properly adjusted whenever any of
the following events occur:
1. At time of "'New Vehicle Inspection/' after
final engine idle adjustments have been made.
2. After any transm ission control linkage has
been removed or replaced.
3. After transmission has been removed and
reinstalled in vehicle.
4. When the transmission is not performing
properly.
G M C S E R V I C E M A N U A L
wear, distortion,
in text refer to
AUTOMATIC TRANSMISSION
TRANSMISSION CONTROL LINKAGE
lubricant recommended in LUBRICATION (SEC. 0)
of this manual.
2. Insert shift rail (2) part way into remote
control cover (17).
3. Position shift finger (18) on shift rail with
offset to the front. Push shift rail the remaining
distance into cover.
4. Install roll pin (19) to retain shift finger
in proper position on shift rail.
5. Position yoke guide (5) in offset of remote
control cover (17). Install washer (4) and nut (3)
on shift yoke guide.
6. Position shift rail yoke (10) and selector
lever (15), with offset toward front, on shift rail
( 2 ).
NOTE: Be sure shift rail yoke engages both
the shift rail and yoke guide (5). With parts
properly aligned install roll pin (12) through
selector lever (15) and shift rail (2).
7. Install washer (14) and nut (13) retaining
selector lever link assembly (16) to selector lever
(15).
8. Install washer (8) and nut (9) retaining
selector lever bell crank (6) to selector lever
link assembly (16).
9. Install expansion plug (1), if removed in
shift rail opening in remote control cover (17).
WARNING
DO NOT START ENGINE WITH
SHIFT LINKAGE DISCONNECTED, AS
SERIOUS INJURY COULD RESULT TO
VEHICLE OR PERSONNEL.
ACCELERATOR AND TV
LINKAGE ADJUSTMENTS
The throttle linkage to transmission must be
properly adjusted so that engine and transmission,
as a matched pair, can give maximum perform­
ance. If transmission throttle linkage is incor­
rectly adjusted, the engine may not operate at full
governed rpm, or the transmission upshift and
downshift points may be incorrect.
Throttle linkage to the transmission should
be adjusted so that transmission upshift occurs
at approximately 50 rpm below engine governed
speed during full throttle operation.
A detent position is incorporated in throttle
linkage to provide additional control of transm is­
sion shifts. If the shift points are not correct
at the "TO-DETENT" position (full throttle),
the linkage requires adjustment. If the "TO-
DETENT" shift points
Sec. 7A
Page 435
are correct, but the