Chevrolet 10 Series 1968, Service Manual

Page: 20 / 713

LUBRICATION 0-17
Positraction
Same as standard axle but use only the special
Positraction lubricant available at your Chevrolet dealer.
40-80 Series
Check lubricant level (including the inter axle dif­
ferential) every 6,000 miles. When necessary, refill to
level of fille r plug hole using “ Multi-Purpose" gear
lubricant meeting U.S. Army Ord. Spec. MIL-L-2105B
as shown in the “ Gear Lubricant Viscosity Chart.”
Drain the lubricant every 24,000 miles. If the vehicle
is operated in exceptionally heavy work or at continuous
high speeds, the lubricant should be changed every
12,000 miles. It may be necessary to change lubricant
more often if vehicle is used off road in dusty areas.
Tw o-Speed A xies
The shift unit should be filled with lubricant to the
fille r opening on the front cover using SAE 10 engine
oil. At ambient temperatures below 0°F., use SAE 5W.
The oil level should be checked every 12,000 miles or
3 months, whichever occurs first.
MASTER CYLINDER
Check master cylinder fluid level every 6,000 miles.
If the fluid is low in the reservoir, it should be filled to
a point about 1/4" from the top rear of each reservoir
with GM Supreme No. 11 Hydraulic Brake Fluid or
equivalent.
FULL AIR BRAKES
Compressor
Remove compressor air strainer and inspect or re­
place every 6,000 miles or oftener. The element can be
cleaned in kerosene or mineral spirits. Cleaners of the
aromatic compound must not be used. The element
should be squeezed (not wrung) dry after cleaning.
Draining Air Tanks
Condensation must be drained from all air tanks
daily. To drain tanks properly, leave drain cocks open
until all air escapes and draining stops. During extreme
cold weather operation, it may be necessary to use an
alcohol evaporator to prevent moisture from freezing
in air tanks.
NOTE: Daily draining is not necessary if truck
is equipped with the optional moisture ejector
valve.
DD2 Safety Actuator
Every month or after 2,000 miles depending on type
of operation check safety actuator.
Every year or after each 50,000 miles, depending on
type of operation, disassemble actuator and clean all
parts. Install new diaphragm, or any other rubber parts,
if they are worn or deteriorated.
Brake Valve
Every Year or 50,000 Miles: Disassemble brake valve
and clean all parts. Install new inlet valves and piston
seal.
Quick Release Valve
Every Year or 50,000 Miles: Disassemble valve, clean
all parts and replace the diaphragm.
Brake Chambers
Every Month or 20,000 Miles: Check travel of brake
chamber push rods and adjust brakes if necessary.
Every Year or 50,000 Miles: Disassemble brake
chambers and clean all parts. Install new diaphragms.
Drain Cocks
A ll drain cocks should be periodically checked for
leakage.
Safety Valve
Every Year or 50,000 Miles: The safety valve should
be removed, disassembled and thoroughly cleaned.
Single Check Valve
Every Year or 50,000 Miles: The check valve should
be dismantled and thoroughly cleaned.
Low Pressure Indicator
Every Month or 10,000 Miles: Check the electrical
connections and the air pressure at which the contacts
close.
Brake Control Valve
Every 200 operating hours or after 5,000 miles or
once each month, lubricate pedal mechanism. Also check
the lever's linkage for adjustment and/or binding.
Every 3,600 operating hours or after each 100,000
miles, clean and replace parts as required.
Every 7,200 operating hours or after 200,000 miles,
or every two years, disassemble brake valve, clean and
inspect all parts. Install new parts where they are found
to be worn or damaged.
Automatic Emergency Valve
Every year or after 50,000 miles, the Automatic
Emergency Valve should be disassembled, cleaned and
lubricated. Rubber parts should be replaced and any
other parts showing signs of wear or damage should
also be replaced.
Double Check Valves
Once a year or every 50,000 miles, the check valve
should be removed, dismounted, and cleaned.
Tractor Protection Valve
Thoroughly check and if necessary clean, replace
parts and lubricate.
Double Check Valve and Stop Lamp Switch
Every month or after 10,000 miles, check the electrical
connections and the operation.
Every year or after 50,000 miles, the combined stop
light switch and double check valve should be dis­
assembled and cleaned and parts replaced as required.
CHEVROLET TRUCK SERVICE MANUAL