Crankcase Ventilation (G Asolin E); Crankcase Ventilation ( D I E S E L ); Multi-Purpose Gear Lubricant Symbol "Mp; Iscosities - GMC 4000 Series Service Manual

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LUBRICATION
STARTER
Some starters are equipped with oiler or plug
at drive end, plug at commutator end, and plug at
middle bearing. At the time of installation, apply
S.A.E. 20 at plugs or oilers.
LINKAGE
Engine oil is used also to lubricate clevis
pins, linkage, clevises, etc. Application should be
made by brush or spray.
AXLE SHIFT UNIT
Remove plug in cover and fill to level of open­
ing with S.A.E. 10 engine oil.
CRANKCASE VENTILATION
GASOLINE ENGINES
The closed positive crankcase ventilation sy s­
tem makes an important contribution to the reduc­
tion of air pollution by recycling fuel fumes, which
enter the crankcase, back to the combustion cham­
ber to be burned, and achieves nearly one-hundred
percent elimination of crankcase em issions - one-
Multi-Purpose Gear Lubricant, meeting U.S.
Army Ord. Specification MIL-L-2105B and indi­
cated by the symbol "MP" on charts, must sa tis­
factorily lubricate heavy duty truck hypoid or bevel
axles, and transm issions, under maximum torque
and speed conditions. It must provide necessary
and suitable load-carrying characteristics to pre­
vent scoring and wear, good stability in storage
and service, and give good resistance to corrosion.
Suppliers should assure these characteristics, and
be responsible for the quality and satisfactory per­
formance of their products.
VISCOSITIES
ROCKWELL AXLES
In Rockwell axles, S.A.E. 140 should be used
the year around except in cases of extremely low
temperatures. If trucks are parked in tempera-
atures below +20°F., or operated in temperatures
consistently below 0°F ., it is advisable to use S.A.E.
90.
OTHER UNITS
S.A.E. 90 may be used the year around. If
truck is operated in temperatures consistently
below 0°F ., use S.A.E. 80. If the truck is operated
in consistently high temperatures (over 100°F.),
S.A.E. 140 may be used.
G M C S E R V I C E M A N U A L
third of total hydrocarbon em issions from vehicle.
into cylinder heads, while valve on In-line engines
is installed in rocker arm cover. At first engine
oil change ventilation valve(s) should be checked
for proper operation as described in GASOLINE
ENGINES (SEC. 6A) under "Crankcase Ventilation
System." Every 12 months or 12,000 m iles, which­
ever occurs first, the valve(s) MUST be replaced.
Also, all hoses and fittings (including flame arrest­
er on In-line engine) should be inspected, cleaned,
and replaced if necessary.
installed at valve rocker arm cover and should be
removed and cleaned at each oil change interval.
DIESEL ENGINE
bly (fig. 12) are installed at opening in rear of
crankcase on diesel engines. A mesh filter element
is contained in a retainer which should be removed
every 30,000 miles and cleaned of accumulations
by immersing repeatedly in fuel oil or cleaning
solvent, until all deposits are removed.
MULTI-PURPOSE GEAR LUBRICANT
(SYMBOL "M P" ON CHARTS)
CHECKING LEVEL
ficient lubricant to bring the level up to filler plug
level. Install and tighten plug. On the forward rear
axle with torque divider, be sure that vehicle has
stood for at least 5 minutes before checking level;
then check level AT REAR FILLER HOLE.
DRAINING AND FILLING
recommended that lubricant be drained after the
first 3,000 m iles of operation, and thereafter at
recommended intervals. Draining at an early m ile­
age removes fine particles of metal or other for­
eign material.
of axle housing, also at bottom of torque divider
or inter-axle differential housing on tandem bevel
axles. Drain when unit is hot, preferably immed­
iately after operation. Reinstall drain plugs.
tandem axles with torque divider, add specified
quantity through filler plug on side of case or add
two pints of lubricant at top of inter-axle differ­
ential housing.
SPECIAL AXLE LUBRICATION
Ventilation valves on "V" engines are threaded
On V6 engines, a crankcase breather (fig. 11) is
Oil separator, breather tube and filter assem ­

REAR AXLE

Remove filler plug and if necessary, add suf­
When axle is new, or after overhaul, it is
At specified intervals remove plug at bottom
Fill axle to level of filler plug opening. On
Special lubrication is required on all axles as