C 1500 Truck 2WD V8-454 7.4L (1990)
Technical Service Bulletin # 903795
Date: 901101
Brake Rotor - Service and Specifications
Number:
90-379-5
Section:
5
Date:
November 1990
Corp. Bulletin No.: 065009
Subject:
BRAKE ROTORS
Model and Year:
1988-90 C/K TRUCKS
TO:
ALL CHEVROLET DEALERS
In the manufacturing of brake rotors, all the tolerances regarding surface finish, parallelism and lateral runout are held very closely. The maintenance of
these tolerances provide the surface necessary to prevent a loss of braking performance. C1, C2, and C3 trucks have a one-piece rotor and hub assembly
with outer and inner bearings. C1 trucks under 5600 GVWR have a 1" rotor. C1 trucks over 5600 GVWR, SS454 trucks (Chevrolet only), C2 and C3
trucks all have 1-1/4" rotors. The rotor on the K2 and K3 with C6P brakes is a complete three piece assembly consisting of a 1-1/4" rotor, bearings and
hub. The rotor on C/K3 with R05 (dual rear wheels) is a complete four piece assembly consisting of a rotor, bearings, hub, and extension. The rotor is
1-1/4" for 88-89 models, 1-1/2" for 90 models. The C3 with R05 is a one piece casting but also has 1-1/4" wide rotors for 88-89 models and 1-1/2" wide
rotors for 90 models. The rotors on the K1 and K2 models are composite construction and require special tool J 37620 when service is required. Light
scoring of the rotor surface not in excess of 0.38 mm (0.015-inch) in depth is normal. This condition will not affect brake operation.
Lateral Runout
Figure 1 - (2WD Model Pictured)