C 2500 Truck 2WD V8-454 7.4L (1988)
Vacuum Brake Booster: All Technical Service Bulletins
Brakes - Improved Pedal Feel
Number:
88-300-5
Section:
5
Date:
JULY, 1988
Subject:
IMPROVED BRAKE PEDAL FEEL
Model and Year:
1988 C/K TRUCKS
TO:
ALL CHEVROLET DEALERS
THIS BULLETIN IS DIVIDED INTO TWO (2) SECTIONS IN ORDER TO ADDRESS SEPARATE CONDITIONS WHICH OCCUR ON
DIFFERENT BRAKING SYSTEMS. BOTH CONDITIONS MAY BE DESCRIBED BY THE CUSTOMER AS BRAKE PEDAL FEEL.
SECTION 1
Improved Brake Pedal Feel - JN3 Brake System:
Some customers may comment of hard brake pedal or lack of assist on some 1988 C/K trucks equipped with JN3 brakes (fourth digit of VIN is "D").
Beginning with the following VIN breakpoints, a new larger displacement brake vacuum booster will be installed on 1988 C/K 10 pickups with JN3
brake system. The new booster is being installed to improve power assist during braking and improve the "feel" of the brakes, especially for customers
who operate their vehicle heavily loaded most of the time.
PLANT
MODEL
VIN BREAK POINT
Ft. Wayne
C15
JZ 256482
K15
JZ 257952
Oshawa
C15
J1 256582
K15
J1 256583
Pontiac
C15
JE 181848
K15
JE 182896
Customers with vehicles built before the VIN breakpoints who operate vehicles heavily loaded may prefer the improved brake pedal feel of the new
booster. If so, the brake booster which is currently being used in production can be installed on vehicles with this condition. When installing the new
booster, follow the procedure in Light Duty C/K Service Manual, Section 5A.
Option
New Booster
Model
Code
Year
Part Number
C/K 1 Under
JN3
1988
18012114
6000 GVWR
(Built before
with P/B
the VIN's)
Use applicable labor operation and time.
SECTION 2
Improved Brake Pedal Feel - JN5 Brake System.
Some customers may comment of a "spongy" or soft brake pedal feel or longer brake pedal travel on some 1988 C/K trucks equipped with JN5 brakes
(fourth digit of VIN is "E") that were built in the Oshawa Assembly Plant between the VIN breakpoints stated below.
Vehicles built between J1206556 and J1233550
In order to improve the brake pedal feel, the master cylinder and brake vacuum booster combination listed below may be installed.
Master Cylinder
New Brake Vacuum Booster
P/N 18013977
P/N 18012114
Labor Operation:
T7660 Labor Time: 1.0 hr