Using the TransFlow Transmission Oil Cooler Flush and Flow Test Tool

GM studies indicate that restricted transmission oil flow is detrimental to the life of any automatic transmission. Plugged oil coolers and oil cooler line restrictions cause insufficient transmission lubrication and elevated operating temperatures that can lead to premature transmission failure. Many repeat repair cases can be prevented by following published procedures for transmission oil cooler flushing and flow checking to ensure there is proper flow through the transmission oil cooler.


The DT-45096 (previously J-45096) TransFlow® transmission oil cooler flush and flow test tool (Fig. 1) can be used to flush and flow test the transmission oil cooler and the oil cooler pipes after the transmission has been removed for repairs. The TransFlow tool is designed to measure oil flow capability within the transmission oil cooler and performs a flow rate test meeting GM flow rate specifications. It is a self-contained unit using a 12-volt flow meter, shop air supply and DEXRON VI automatic transmission fluid (ATF).


Fig. 1


The DT-45096 TransFlow tool uses conventional automatic transmission fluid as the cleaning agent. It doesn’t use any detergents, chemical cleaning agents or hot water, so there is no hazardous waste to dispose of.


If the transmission fluid requirement for the vehicle is different than DEXRON VI, flushing the cooler with DEXRON VI is an acceptable service procedure. Very little fluid remains in the cooler after the flush procedure. After performing the flush and flow test, use compressed air to blow the residual transmission fluid out of the oil cooler and lines.


Time allowance for performing the transmission oil cooler flushing and flow checking procedure has been included in the appropriate labor time guide operations since the 1987 model year.


The DT-45096 TransFlow includes:

  • 32 quart (30 liters) supply vessel
  • 34 quart (32 liters) waste oil vessel
  • Air pressure supply fitting
  • Digital flow rate indicator
  • 12V DC power cable
  • Black supply oil hose with quick connect fitting
  • Clear waste oil hose with quick connect fitting


TIP: A new Operation Manual has just been released with updated information along with a new Adapter Application Chart. The new manuals are available under the Support tab for the DT-45096 (previously J-45096) tool at (Fig. 2)


Fig. 2




The TransFlow equipment is connected to the vehicle’s transmission oil cooler lines using the current cooler line adapters. Two adapters are included with the TransFlow. Five other adapters also are available. The most commonly used adapters are the DT-45096-30 (for 6-speed, 8-speed and 10-speed longitudinally-mounted transmissions) (Fig. 3) and DT-45096-50 (for 6-speed and 9-speed transverse-mounted transmissions). (Fig. 4)


Fig. 3


Fig. 4


In the flush mode, air pressure forces clean transmission fluid through the oil cooler and lines, removing dirty oil and blockages. To enhance the cleaning action, the oil is agitated with bursts of air. The cooler is flushed first in the backflush direction, then the normal flow direction. Waste oil is collected in a built-in waste tank.


Flow Test


After flushing, use the digital flow rate indicator in the DT-45096 to perform a flow test. The flow test indicates whether the oil cooler and cooler lines still have restrictions, which must be addressed before the repair is completed.


An electronic flow meter is used to measure the minimum flow capability of the transmission oil cooling system. A digital display indicates the ATF flow rate in gallons per minute (GPM) along with the amount of ATF in the supply vessel, supply vessel ATF temperature, machine cycles and the operating mode.


Insufficient oil flow through the transmission oil cooling system will cause premature transmission failure. The required minimum ATF flow rate reading is directly related to the supply oil temperature. In addition to transmission fluid temperature, minimum flow rates vary depending on whether the oil cooler is made of aluminum or steel.


Refer to the flow rate chart for the oil flow rate specification based on the temperature of the ATF in the supply vessel. The User’s Manual and the Service Information include minimum flow rate charts. Refer to the appropriate Service Information for complete flow rate information for the model and cooling system being tested.


The published flow rates are based on the tool calibrated at 2.0 GPM (7.6L/minute) using ATF at 65° F (18° C) with 90 psi of air pressure. Dealership tools should be calibrated using the same specifications. (Fig. 5) If the tool is set up with higher temperature ATF, then artificially high flow rates could be seen. Remember, the tool is only measuring minimum flow rates. Fluid warmer than room temperature may result in higher self-test readings.


Fig. 5


The entire flushing and flow test procedure takes only 5-8 minutes. The waste tank can be emptied either using a suction hose in the port provided or by draining from the built-in drain fitting at the bottom of the tank. In either case, the waste oil can be disposed of the in the same manner as any other drained transmission fluid.


After the flow test, the following information is displayed:

  • Tested flow rate in GPM
  • Temperature in degrees Fahrenheit
  • Cycle number
  • 7 or 8-digit alpha/numeric flow code. This flow code must be written on the repair order for the warranty claim.


Self-Test Flow Rate


If an oil cooler fails the flow test, repeat the flow test to confirm the condition. If it fails again, disconnect the tool from the cooler lines and run the TransFlow self-test procedure to verify flow is 2.0 GPM (7.6L/minute) or greater using ATF at 65° F (18° C) with a minimum 90 psi of air pressure. The self-test should take no more than two minutes to complete.


TIP: Refer to the Useful Information/Helpful Hints section of the User’s Manual for additional information on the self-test procedure.


If you are having difficulty obtaining the 90 psi of shop air required to run the TransFlow tool:

  • Connect an accurate pressure gauge between the TransFlow air inlet and the shop to verify the pressure going into TransFlow from the shop air supply is at least 90 psi and there are no obstructions in the shop line.
  • Connect TransFlow to an air line that is closer to the service compressor.
  • Check the service compressor’s pressure.
  • Connect to the body shop air line, which may be at a higher pressure.


Transmission Fluid Temperature


The ATF in the supply vessel must be greater than 65° F (18° C). This is the minimum required operating temperature. Below 65° F (18° C), the TransFlow will shut off. Below this temperature, it is difficult to accurately measure the flow of transmission fluid.


– Thanks to Chuck Berecz, Mark Kevnick and Dan Popoff

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  1. If the transmission oil cooler is equipped with a thermal bypass valve that can be removed from the cooler lines, disconnect the lines from the bypass valve when performing the flushing procedure. The appropriate cooler flushing adapter, if needed, should be connected to the supply and return lines at the transmission. Refer to the Service Information for the applicable adapters. If the transmission oil cooler system has a thermal bypass valve that cannot be disconnected during a flush and flow test, the observed flow rate may be higher than the published flow rates in the Service Information.

  2. Thermal limiters should be removed prior to flushing lines and cooler. Incorrect data and or high flow rates will result.