Subject: Vacuum Modulator Spring Throttle Valve Inner Spring
Model and Year: 1954 Powerglide Transmission
Source: Chevrolet Technical Service Bulletin
Bulletin No: DR - 165
Section: VII
Date: January 29, 1954
TO: ALL CHEVROLET DEALERS
1954 Powerglide Transmissions built after Serial Number C106D will have the same up and down shifting characteristics as the 1953 Unit.
The Vacuum Modulator Spring used in the 1954 Powerglide Transmission has been replaced by 1953 spring and Throttle Valve Inner Spring is omitted.
SERVICE
In cases where an objectionable severe downshift or "clunk" is encountered in transmissions built prior to above serial number, the 1953 Vacuum Modulator Spring should be installed and the Throttle Valve Inner Spring removed.
PARTS
Description : Vacuum Modulator Spring (1953 and late 1954)
Part No : 3691669
Early 1954 Vacuum Modulator Spring is identified by an orange stripe.
There is no identification mark on the 1953 spring which is shorter than the 1954 early spring.
E.L. Harrig
Manager, Service and Mechanical Department
Article ID: 1126
Created: January 24, 2015
Last Updated: January 24, 2015
Online URL: https://www.corvetteactioncenter.com/tech/knowledgebase/article/1954-corvette-service-bulletin-vacuum-modulator-spring-throttle-valve-inner-spring-1126.html