A/T - Oil Cooler Flushing and Flow Check Procedures: Overview

File In Section: 07 - Transmission/Transaxle

Bulletin No.: 99-07-30-017

Date: September, 1999

INFORMATION

Subject:
Automatic Transmission Oil Cooler Flushing and Flow Check Procedures

Models:
1999 and Prior GM Vehicles with Automatic Transmissions

This bulletin is being revised to add the 1998-1999 Model Years. Please discard Corporate Bulletin Number 77-71-59 (Section 7 - Transmission).

GM studies indicate that plugged or restricted transmission oil coolers and pipes cause insufficient transmission lubrication and elevated operating temperatures which can lead to premature transmission wear-out. Many cases could have been prevented by following published procedures for transmission oil cooler flushing and flow checking. This procedure includes flushing and flow checking the auxiliary transmission oil cooler, if equipped. GM requires that transmission oil cooler flushing and flow checking be performed whenever a transmission is removed from the vehicle for service within warranty, including:

^ Goodwrench SRTA
^ Major overhaul
^ Torque converter replacement
^ Oil pump replacement

Only GM Goodwrench DEXRON(R)-III automatic transmission fluid should be used when doing warranty repair on GM transmissions.

Time allowance for performing the cooler flushing and flow checking procedure has been included in the appropriate labor time guide operations since the 1987 model year. The service procedure steps for oil cooler flushing are as follows:

Cooler Flushing and Flow Check Steps

^ Equipment needed
^ Preparation
^ Initial flush
^ Back flush
^ Flow check
^ Clean-up Equipment needed





Table 1: Direction Of Fluid Flow In The Oil Cooler Pipes At The Transmission