Chevrolet 10 Series 1968, Service Manual

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BRAKES 5-17
F ig . 3 1 —Parking Brake Hand Lever—T-M odels
displacement requirements for each vehicle line. There­
fore, it is necessary that correct parts be used when
replacing either complete main cylinder assemblies or
the component pistons of these assemblies.
There are two sources for dual main cylinders used on
1968 Chevrolet vehicles: Delco Moraine and Bendix. The
Bendix unit can be readily identified by a ‘Secondary
Piston Stop’ bolt on the bottom of the casting. Delco
Moraine main cylinders do not have this bolt. (See
chart.)
The displacement capabilities of a particular cylinder
are specified by the two letters which are stamped in the
metal on the top of the closed end of the main cylinder
barrel. Main cylinders should only be replaced with
a n o t h e r cylinder b e a r i n g the s a me two-letter
identification.
The length of the secondary pistons in these main cyl­
inders is a critical factor in the displacement capabilities
of a particular main cylinder. These secondary pistons
are coded, using rings or grooves in the shank or center
section of the piston. Refer to the chart below for proper
identification.
The primary pistons are of two types. One has a deep
socket for the push rod and the other a very shallow
socket.
It is mandatory that replacement pistons be identical
to the original piston. This can be verified by checking
the identification marks on the secondary piston and the
socket contour of the push rod end of the primary
piston. (See Chart below).
Model Source Brake Type
Master
Cylinder
Code
Secondary
Piston
Identification
Light
Trucks
Delco
Moraine
Manual-Drum AB
4 Rings
or Grooves
Bendix Power Drum
AB 3 Rings
Delco
Moraine
Manual-Drum NF
5 Rings
or Grooves
Bendix
Manual-Drum
NF 2 Grooves
Power -Drum NF 5 Rings
BRAKE MAIN CYLINDER IDENTIFICATION
CHEVROLET TRUCK SERVICE MANUAL