Source: Chevrolet Service Technical Bulletin
Subject: Powerglide Transmission Slippage and Chatter in Automatic Low and Drive Range
Model and Year: 1953 Corvette
Bulletin Number: DR - 145
Section: June 24, 1953
TO: ALL CHEVROLET DEALERS
Slippage and chatter in Powerglide Transmission on medium and full throttle in both Automatic Low and Automatic Drive Ranges will exist when there is no oil drain hole in the Modulator Housing.
Oil seeping by the modulator piston builds up against diaphragm preventing the diaphragm spring from raising main line pressure and pressure in the Low Apply and clutch circuits under medium and full throttle acceleration.
The modulator body should have a drain hole 3/8" in diameter one inch directly below the center line of the modulator piston. Any housing found without the drain hole may be drilled in the dealership.
Manager, Service and Mecahnical Department
Article ID: 81
Created: July 4, 2014
Last Updated: July 4, 2014
Online URL: https://www.corvetteactioncenter.com/tech/knowledgebase/article/1953-corvette-service-bulletin-powerglide-transmission-slippage-and-chatter-in-automatic-low-and-drive-range-81.html