Chevrolet 70 1969 Series, Shop Manual

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TRANSMISSIONS AND CLUTCHES 7B-14
OIL LEAKS
1. Oil level too high.
2. Wrong lubricant in unit.
3. Non-shielded bearing used at front or rear
bearing cap. (Where applicable.)
4. Seals (if used) defective or omitted from
bearing cap, wrong type seal used, etc.
5. Transmission breather omitted, plugged
internally, etc.
6. Cap screws loose, omitted or missing
from remote control, shifter housing, bearing
caps, power take-off, or covers, etc.
7. Welch “ seal" plugs loose or missing en­
tirely from machine openings in case.
8. Oil drain-back openings in bearing caps or
case plugged with varnish, dirt, covered with gas­
ket material, etc.
9. Broken gaskets, gaskets shifted or squeezed
out of position, pieces still under bearing ca.ps,
clutch housing, power take-off, and covers, etc.
10. Cracks or holes in castings.
11. Drain plug loose.
BEARING FAILURES
More than 9 0 % of all bearing failures are
caused by dirt which is always abrasive.
Dirt may enter the bearings during assembly
of the units or be carried into the bearing by the
lubricant while in service. Dirt may enter through
seals, breather or even dirty containers used for
addition or change of lubricant.
Softer material such as dirt, dust, etc., us­
ually form abrasive paste or lapping compounds
within the bearings themselves since the unit
pressure between the balls and raceways makes a
perfect pulverizer. The rolling motion tends to
entrap and hold the abrasives. As the balls and
raceways wear, the bearings become noisy. The
lapping action tends to increase rapidly as the fine
steel from the balls and rollway adds to the lap­
ping material.
Hard coarse material such as chips, etc., may
enter the bearings during assembly from ham­
mers, drifts, power chisels, etc., or be manu­
factured within the unit during service from
raking teeth, etc. These chips produce small in­
dentation in balls and races. Jamming of these
hard particles between balls and races may cause
the inner race to turn on shaft, or the outer race
to turn in the housing.
C O R R O SIO N
Water, acid, and corrosive materials formed
by deterioration of lubricant, will produce red­
dish-brown coating and small etched holes over
outer and exposed surfaces of race. Corrosive
oxides also act as lapping agent.
FA T IG U E
All bearings are subject to fatigue and must
be replaced eventually. Your own operating ex­
perience will dictate mileage replacement of bear­
ings showing only normal wear.
S H A F T S FITS
Excessive looseness under load is very ob­
jectionable because it produces a creeping or slip­
ping of the inner ring on the rotating shaft. This
causes the surface metal of shafts to scrub or
wear off.
Bearing fits on rotating shafts are usually
specified as tight. When play or looseness, even
.001", exists between the bearing and shaft, there
is a very powerful force tending to rotate the in­
ner race on the shaft; this force is caused by the
looseness or lost motion between the parts and
disappears when no looseness exists.
TRANSMISSION REPLACEMENT-MANUAL TRANSMISSONS
The procedures required to remove the man­
ual transmission from trucks covered in this
manual are dependent generally upon the type of
cabs (i.e., conventional or tilt), type of body, and
lifting equipment available in the repair shop.
Operations other than those included in this sec­
tion may be necessary if the vehicle has special
equipment such as a power take-off unit and
controls, etc.
The required operations will be obvious upon
visual inspection of the vehicle. The instructions
contained herein under “ Removal" and “ Installa­
tion" will serve as a guide in accomplishing
transmission replacement.
It is important to note that vehicles covered
by this manual will have either an “ Apron" or
“ S .A .E . #2” type flywheel housing as shown in
figure 1. The “ Apron" type flywheel housing is
easily identified by the sheet metal pan which
covers the entire lower portion of the clutch
housing. Note lack of a separate clutch housing.
The “ S .A .E . #2” type flywheel housing com­
pletely surrounds the flywheel. A separate clutch
housing is used in addition to the flywheel housing.
Transmission replacement procedures are dif­
ferent for each type flywheel housing used.
R E M O V A L
1. On tilt cab models, disconnect shift linkage
from remote control assembly at transmission.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SH O P M A N U A L