Changes in Transmission Oil Cooler Flush Requirements

Recent GM studies have shown that automatic transmission oil cooler flush requirements have limited benefit on many current transmission repairs. Based on the studies, GM will no longer require a mandatory flush and flow test of the transmission oil cooler and the oil cooler pipes — including the auxiliary transmission oil cooler, if equipped — to be performed in every instance of transmission or torque convertor replacements or internal transmission repairs. (Fig. 1) As a result of this policy change, transmission repairs will be simpler, the environmental impact of waste oil will be reduced and Global Warranty Management transaction processing will be simplified.

Fig. 1


Transmission Repair Policy Changes

Effective December 1st, 2018:

  • Job cards will no longer require a transmission flush code from the DT-45096 Transmission Oil Cooling System Flush and Flow Test Tool (DT-45096 TransFlow® machine). (Fig. 2)
  • The Flush Code field in Global Warranty Management related to all applicable transmission labor operations should be left blank. The field will be eliminated mid-December.
  • The Warranty Support Center will no longer require a flush code on warranty transactions.

Repair procedures in the Service Information will be updated to reflect the elimination of the transmission cooler flush requirement. In addition, related service bulletins, the labor time guide, and the GM Service Policies and Procedures Manual will be updated accordingly.

Fig. 2

The DT-45096 TransFlow machine continues to be a valuable GM Essential Tool that should be used when diagnosing transmission overheating conditions or a transmission failure due to a lack of lubrication. Technicians should continue to document the TransFlow code in the correction comments of the job card in instances when the DT-45096 flow test procedure is used to diagnose an overheating or lubrication concern.

TIP: Use only the appropriate GM automatic transmission fluid when performing a transmission repair. If the fluid in the DT-45096 TransFlow machine is different than what is used in the transmission, after performing the flush and flow test, use compressed air to blow the residual transmission fluid out of the transmission oil cooler and lines.

New Fluid Exchange Procedure

A new repair procedure for the DT-45096 TransFlow machine to exchange fluid also has been developed to address torque converter clutch shudder on 8L45 and 8L90 8-speed automatic transmissions (RPOs M5T, M5N, M5U, M5X). The new transmission fluid exchange procedure and new formula of Mobil 1 Synthetic LV ATF HP transmission fluid is being rolled out regionally due to the limited availability of both the new transmission fluid and tool kit. It is anticipated that the new transmission fluid and tool kit will be available nationwide by late January or early February 2019. Look for more information to be released soon in a service bulletin and the December 2018 Emerging Issues seminar (10218.12V).

– Thanks to Mark Gordon

Updated December 13, 2018

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  1. The only issues recently we have run into are the auxiliary coolers on full size SUV (Tahoe/Suburban/Yukon/Escalade) where the condenser/aux. cooler has been clogged, and unable to be freed up. There have been two instances in the last 3-5 months. In my opinion, and as Ed said above, when in doubt, double check. OLH should be authorized in these cases.

  2. In 10 years as a trans tech I can count on one hand the number of times I have had a plugged cooler, all were g vans gas engines and commercial. If we do a proper repair verification/ break in road test an over heat condition should present it’s self fairly quickly. I’ll be the first one to say I am guilty of skimming on that, but it’s one of those back to basics things we tend to neglect.

  3. There are instances of restricted coolers and lines but when GM researched this it found that the occurrence is very low. If you feel that a flow check and flush is warranted based on a particular failure or your experience, you can continue to perform these operations and use Other Labor Hours (OLH) to cover your time. Thank you for taking the time to contact us and, hopefully, this answers your question.

  4. Todd Wentworth says:

    Hard to believe this. The last torque converter replacement I had showed no debris in pan,little on top of filter. When flushing coolers there was no flow. Found that cooler line set was plugged @ hose/pipe swage. Lines could not be cleared resulting in replacement.Transmission would have been overheated/damaged if lines & cooler weren’t flushed.

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