GMC 1982 Light Duty Truck, Service Manual

Page: 1156 / 1435

7B-2 MANUAL TRANSMISSION
bearings within the gear is maintained by a tubular spacer in
the center and four thrust washers (one being used between
the rows of roller bearings and one at each end). The
countershaft is not a press fit in the case bores, but has
.127mm (.005 inch) diameter clearance. An expansion plug
is pressed into a counter bore at the front of the case to
prevent oil leakage around the countershaft.
The reverse idler gear is supported on a bronze
bushing, pressed into the gear. A magnetic disc is attached
to bottom, near rear of case under countershaft gear. This
magnet collects and prevents circulation of chips in
transmission oil.
4-Speed 117mm (Fig. 7B4-4)
The 117mm, Model CH 465 truck transmission uses a
constant mesh first gear that engages with the second speed
synchronizer sleeve. Second, third and fourth gears are
synchronized. The clutch gear is supported by a heavy duty
ball bearing. The forward end of the mainshaft is supported
by a loose collar-type bearing inside the clutch gear, while
the rear is carried on a ball bearing in the case. End play is
taken up by the rear flange retaining nut. The countergear is
supported at the rear of a single row ball bearing which
takes the thrust load, and by a roller bearing at the front.
Incorporated in the cover is a ball pin type interlock which
prevents simultaneous engagement of two gears. As one rod
is moved, it pushes a ball out that engages the other two rods
to prevent their movement.
Gearshift levers on manual transmissions are located
either on the steering column or on the floorpan. Regardless
of location, the lever performs two operations: It selects the
gear assembly to be moved, and moves it either forward or
backward into the desired gear position. The transmission
action is the same whether a floor-type shift lever or a
steering column shift lever is used. When the shift lever is
moved, the movement is carried by linkage to the
transmission.
MAINTENANCE AND ADJUSTMENTS
Preliminary Inspection
Before attempting to repair the clutch, transmission or
related linkages for any reason other than an obvious
failure, the problem and probable cause should be identified.
A large percentage of clutch and manual transmission
problems are manifested by shifting difficulties such as high
shift effort, gear clash and grinding or transmission
blockout. When any of these problems occur a careful
analysis of these difficulties should be accomplished, and the
following checks and adjustments performed in the
presented sequence before removing the clutch or
transmission for repairs.
CLUTCH ADJUSTMENT
Clutch Free Pedal Travel
1. The clutch free pedal travel adjustment should be made
as outlined in Section 7C.
2. Check clutch linkage for lost motion caused by loose or
worn swivels, deflection of mounting brackets or
damaged cordon shaft.
Clutch Spin Down Time
1. Run the engine at a normal idle with transmission in
neutral and clutch engaged.
2. Disengage the clutch, wait nine seconds and shift the
transmission to reverse. No grinding noise should be
heard. A grinding noise indicates incorrect clutch
adjustment, lost motion, clutch misalignment, or
internal problems such as failed dampers, facings,
cushion springs, diaphragm spring fingers, pressure
plate drive straps, etc.
SHIFT LINKAGE ADJUSTMENT
Steering Column Shift Control
1. Remove the shift control rods from the column levers.
2. Check shift effort at the shift control lever knob. (Effort
should nGt exceed 2 lb. with transmission linkage
removed.)
3. If binding is felt, refer to the adjustment procedure for
the steering column lower bearing in Section 3B.
4. Lubricate all rod and swivel connections and recheck
shift effort afer installation.
5. If shift linkage is free from binding, the column levers
should be checked for end play. A .005" feeler gage
should fit between the levers and control lever.
6. Connect control rods and check steering column control
levers for alignment. In neutral, the column control
lever tangs should line up with the slot in the main
control lever.
Floor Shift Control
All swivels, rods and mountings should be checked for
lost motion and repaired or replaced as necessary.
Transmission control levers should be checked for wear and
repaired or replaced as necessary.
TRANSMISSION SHIFT EFFORT
Transmission Shift Effort Checking Procedures
1. Remove the shift rods at the transmission and align the
sleeve, blocker ring and gear by shifting into the
offending gear and then back into neutral.
2. Check the torque required to shift into gear with an
inch pound torque wrench on the shift lever attaching
bolt. If more than the specified torque 5 N-m (50 in.
lbs.) is required, the transmission shift lever should be
checked for rust or dirt binding the lever.
3. Clean levers, lubricate and recheck the torque value.
NOTICE:
If at this point in the procedure, it is found
that high shift effort or blockout still exists, an anti­
chatter lubricate (positraction additive) should be used.
The lubricant is available in a plastic bottle and can be
squirted in the transmission through the filler plug.