Automatic Transmission Cooling System Chevrolet Express G2500

Transmission Fluid Temperature Sensor Specifications

Transmission Fluid Temperature Sensor Specifications

Transmission Overheats

Transmission Overheats

Transmission Fluid Cooler Flushing and Flow Test (J 45096 4L60-E)

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 failure. Many repeat repair cases could have been prevented by following published procedures for transmission oil cooler flushing and flow checking. This procedure includes flow checking and flushing the auxiliary transmission oil cooler, if equipped.

Note. Use the J 45096 flow test tool or equivalent to flush and flow test the transmission oil cooler and the oil cooler pipes after the transaxle is removed for repairs.

Only GM Goodwrench DEXRON®VI automatic transmission fluid should be used when doing a repair on a GM transmission.

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

Cooler Flow Check and Flushing Steps

1. Machine Set-up
2. Determine Minimum Flow Rate
3. Back Flush
4. Forward Flush
5. Flow Test
6. Code Recording Procedure
7. Clean-up

Special Tools

1. J 35944-200 Cooler Flushing Adapter
2. J 45096 Transmission Oil Cooling System Flush and Flow Test Tool
3. Shop air supply with water/oil filters, regulator and pressure gauge-minimum 90 psi
4. Eye protection
5. Rubber gloves

Machine Set-up

1. Verify that the main power switch (1) is in the OFF position.
2. Place the main function switch (2) in the IDLE position.
3. Connect J 45096 flow test tool to the vehicle 12-volt DC power source by connecting the red battery clip to the positive (+) battery post on the vehicle and connect the negative (-) lead to a known good chassis ground.
4. Turn the main power switch to the ON position.
5. Fill the supply tank with Dexron®VI, or equivalent, through the fill port.
6. Install and tighten the fill cap.
7. Connect a shop air supply hose to the quick-disconnect on the rear panel marked SUPPLY AIR.

Determine Minimum Flow Rate

1. From the machine display, identify the temperature of the automatic transmission fluid that is stored in the supply vessel of J 45096 flow test tool.
2. Determine whether the transmission oil cooler is steel or aluminum by using a magnet (1) at the cooler flange (2) at the radiator.
3. Refer to the table below. Using the temperature from step 1, locate on either the Steel MINIMUM Flow Rate table or the Aluminum MINIMUM Flow Rate table the minimum flow rate in gallons per minutes (GPM). Record the minimum flow rate in GPMs and the supply fluid temperature for further reference. Example: Fluid temperature: 24°C (75°F) Cooler type: Steel The MINIMUM flow rate for this example would be 0.8 GPM.
4. Inspect transmission oil cooler lines for damage or kinks that could cause restricted oil flow. Repair as needed and refer to the appropriate GM service manual procedures.

Minimum Flow Rate in Gallons Per Minute (GPM)

Back Flush Procedure

1. Connect the J 45096 flow test tool adapters (1) to the vehicle transmission oil cooler supply and return lines at the transmission, may require J 35944-200 adapter.
2. Connect the black supply hose (1) to the return line, top connector of the transmission, and the clear waste hose (2) to the feed line, bottom connector of the transmission, to the vehicle cooler lines. This is the reverse flow backflush direction.
3. Turn the main function switch to the FLUSH position. Allow the machine to operate for 30 seconds.
4. Turn the main function switch to the IDLE position and allow the supply vessel pressure to dissipate.

Forward Flush

1. Disconnect the supply and waste hoses from the vehicle cooler lines. Reverse the supply and waste hoses to provide a normal flow direction.
2. Turn the main function switch to the FLUSH position and allow the machine to operate for 30 seconds.

Flow Test

1. Turn the main function switch to the FLOW position and allow the oil to flow for 15 seconds. Observe and note the flow rate. This is the TESTED flow rate.
2. Compare the TESTED flow rate to the MINIMUM flow rate information previously recorded. If the TESTED flow rate is equal to or greater than the MINIMUM flow rate recorded, the oil cooling system is functioning properly. Perform Code Recording Procedure. If the TESTED flow rate is less than the MINIMUM flow rate previously recorded, repeat the back flush and forward flush procedures.
3. If the TESTED flow rate is less than the MINIMUM flow rate after the second test, perform the Code Recording Procedure. Replace the transmission oil cooler. Connect the supply and waste hoses to the cooler lines in the normal flow direction. Perform the Flow Test. Perform the Code Recording Procedure.

Code Recording Procedure

1. Turn the main function switch to the CODE position.
2. Record TESTED flow rate, temperature, cycle and seven-character flow code information on the repair order.

Clean-Up

1. Turn the main function switch to the IDLE position and allow the supply vessel pressure to dissipate.
2. Turn the main power switch to the OFF position.
3. Disconnect the supply and waste hoses and the 12-volt power source from the vehicle.
4. Disconnect the air supply hose from J 45096 flow test tool.
5. Dispose of the waste oil in accordance with all applicable federal, state, and local requirements.

Transmission Fluid Cooler Flushing and Flow Test (6L90)

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 failure. Many repeat repair cases could have been prevented by following published procedures for transmission oil cooler flushing and flow checking. This procedure includes flow checking and flushing the auxiliary transmission oil cooler, if equipped.

Note. Use the J 45096 flush and flow test tool or equivalent to flush and flow test the transmission oil cooler and the oil cooler pipes after the transaxle is removed for repairs.

Only GM Goodwrench DEXRON®VI automatic transmission fluid should be used when doing a repair on a GM transmission.

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

1. Machine Set-up
2. Determine Minimum Flow Rate
3. Back Flush
4. Forward Flush
5. Flow Test
6. Code Recording Procedure
7. Clean-up

Special Tools

1. DT 45096 Transmission Oil Cooling System Flush and Flow Test Tool
2. DT 45096-30 Transmission Cooler Flush Adapter
3. Shop air supply with water/oil filters, regulator and pressure gauge - minimum 90 psi
4. Eye protection
5. Rubber gloves

For equivalent regional tools, refer to Special Tools .

1. Verify that the main power switch (1) is in the OFF position.
2. Place the main function switch (2) in the IDLE position.
3. Connect DT 45096 flush and flow test tool to the vehicle 12V DC power source by connecting the red battery clip to the positive, +, battery post on the vehicle and connect the negative lead to a known good chassis ground.
4. Turn the main power switch to the ON position.
5. Fill the supply tank with Dexron®VI through the fill port.
6. Reinstall and tighten the fill cap.
7. Connect a shop air supply hose to the quick-disconnect on the rear panel marked SUPPLY AIR.

1. From the machine display, identify the temperature of the automatic transmission fluid that is stored in the supply vessel of DT 45096 flush and flow test tool.
2. Determine whether the transmission oil cooler is steel or aluminum by using a magnet (1) at the cooler flange (2) at the radiator.
3. Refer to the table below. Using the temperature from step 1, locate on either the Steel MINIMUM Flow Rate table or the Aluminum MINIMUM Flow Rate table the minimum flow rate in gallons per minutes (GPM). Record the minimum flow rate in GPMs and the supply fluid temperature for further reference. Example Fluid temperature: 75°F Cooler type: Steel The MINIMUM flow rate for this example would be 0.8 GPM.
4. Inspect transmission oil cooler lines for damage or kinks that could cause restricted oil flow. Repair as needed and refer to the appropriate GM service manual procedures.

Minimum Flow Rate in Gallons Per Minute (gpm)

1. Connect the DT 45096-30 cooler flush adapter (1) to the vehicle transmission oil cooler supply and return lines at the transmission.
2. Connect the black supply hose (1) to the return line, bottom connector of the transmission, and the clear waste hose (2) to the feed line, top connector of the transmission, to the vehicle cooler lines. This is the reverse flow - backflush direction.
3. Turn the main function switch to the FLUSH position. Allow the machine to operate for 30 seconds.
4. Turn the main function switch to the IDLE position and allow the supply vessel pressure to dissipate.

1. Disconnect the supply and waste hoses from the vehicle cooler lines. Reverse the supply and waste hoses to provide a normal flow direction.
2. Turn the main function switch to the FLUSH position and allow machine to operate for 30 seconds.

1. Turn the main function switch to the FLOW position and allow the oil to flow for 15 seconds. Observe and note the flow rate; this is the TESTED flow rate.
2. Compare the TESTED flow rate to the MINIMUM flow rate information previously recorded. If the TESTED flow rate is equal to or greater than the MINIMUM flow rate recorded, the oil cooling system is functioning properly. Perform Code Recording Procedure. If the TESTED flow rate is less than the MINIMUM flow rate previously recorded, repeat the back flush and forward flush procedures.
3. If the TESTED flow rate is less than the MINIMUM flow rate after the second test, perform Code Recording Procedure. Replace the transmission oil cooler. Reconnect supply and waste hoses to the cooler lines in the normal flow direction. Perform Flow Test. Perform Code Recording Procedure.

1. Turn the main function switch to the CODE position.
2. Record TESTED flow rate, temperature, cycle and seven-character flow code information on repair order.

1. Turn the main function switch (2) to the IDLE position and allow the supply vessel pressure to dissipate.
2. Turn the main power switch (1) to the OFF position.
3. Disconnect the supply and waste hoses and the 12-volt power source from the vehicle.
4. Disconnect the air supply hose from J 45096 flush and flow test tool.
5. Dispose of the waste ATF in accordance with all applicable federal, state, and local requirements.

Removal Procedure

1. Remove the grille assembly. Refer to «Grille Replacement (Base)»(/chevrolet/express-g2500/2013-2013/remont/exteriorinterior-trim/#exterior-trim) , «Grille Replacement (Uplevel)»(/chevrolet/express-g2500/2013-2013/remont/exteriorinterior-trim/#exterior-trim) .
2. If equipped with an ambient temperature sensor, remove it from the bracket. Refer to «Ambient Air Temperature Gauge Sensor Replacement»(/chevrolet/express-g2500/2013-2013/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges) .
3. Place a drain pan under the vehicle.
4. Remove the cooler kit assembly, if equipped.
5. Disconnect the transmission oil cooler lines from the auxiliary oil cooler.
6. Remove the oil cooler lines from the auxiliary oil cooler. Refer to «Transmission Fluid Cooler Hose/Pipe Replacement (4L60-E/4L65-E/4L70-E)»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-cooling-system) , «Transmission Fluid Cooler Hose/Pipe Replacement (6L90 MYD)»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-cooling-system) .
7. Remove the 4 bolts securing the auxiliary oil cooler to the radiator support.
8. Remove the auxiliary oil cooler.

Installation Procedure

1. Install the 4 bolts securing the oil cooler to the radiator support and tighten to 10 N.m (89 lb in).
2. Install the oil cooler lines to the auxiliary oil cooler and tighten to 23 N.m (17 lb ft). Refer to «Transmission Fluid Cooler Hose/Pipe Replacement (4L60-E/4L65-E/4L70-E)»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-cooling-system) , «Transmission Fluid Cooler Hose/Pipe Replacement (6L90 MYD)»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-cooling-system) .
3. Install the cooler kit assembly, if equipped.
4. Remove the drain pan.
5. If equipped with an ambient temperature sensor, install it to the bracket. Refer to «Ambient Air Temperature Gauge Sensor Replacement»(/chevrolet/express-g2500/2013-2013/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges) .
6. Install the grille assembly. Refer to «Grille Replacement (Base)»(/chevrolet/express-g2500/2013-2013/remont/exteriorinterior-trim/#exterior-trim) , «Grille Replacement (Uplevel)»(/chevrolet/express-g2500/2013-2013/remont/exteriorinterior-trim/#exterior-trim) .

1. Pull the plastic cap back from the quick connect fitting and down along the cooler line about 5 cm (2 in).
2. Using a bent-tip screwdriver, pull on one of the open ends of the retaining ring in order to rotate the retaining ring around the quick connect fitting until the retaining ring is out of position and can be completely removed.
3. Remove the retaining ring from the quick connect fitting.
4. Discard the retaining ring.
5. Pull the cooler line straight out from the quick connect fitting.

1. Install a new retaining ring into the quick connect fitting using the following procedure
2. Hook one of the open ends of the retaining ring in one of the slots in the quick connect fitting.
3. Rotate the retaining ring around the fitting until the retaining ring is positioned with all three ears through the three slots on the fitting.
4. Do not install the new retaining ring onto the fitting by pushing the retaining ring.
5. Ensure that the three retaining ring ears are seen from inside the fitting and that the retaining ring moves freely in the fitting slots.
6. Install the cooler line into the quick connect fitting.
7. Insert the cooler line end into the quick connect fitting until a click is either heard or felt.
8. Do not use the plastic cap on the cooler line in order to install the cooler line into the fitting.
9. Pull back sharply on the cooler line in order to ensure that the cooler line is fastened into the quick connect fitting.
10. Position (snap) the plastic cap onto the fitting. Do not manually depress the retaining ring when installing the plastic cap onto the quick connect fitting.
11. Ensure that the plastic cap is fully seated against the fitting.
12. Ensure that no gap is present between the cap and the fitting.
13. Ensure that the yellow identification band on the tube is hidden within the quick connect fitting.
14. A hidden yellow identification band indicates proper joint seating.
15. Fill the transmission to the proper level with DEXRON® VI transmission fluid. Refer to «Transmission Fluid Level and Condition Check»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-4l60-e-m30-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .

1. Pull the plastic cap back from the quick connect fitting and down along the cooler line about 5 cm (2 in).
2. Using a bent-tip screwdriver, pull on one of the open ends of the retaining ring in order to rotate the retaining ring around the quick connect fitting until the retaining ring is out of position and can be completely removed.
3. Remove the retaining ring from the quick connect fitting.
4. Discard the retaining ring.
5. Pull the cooler line straight out from the quick connect fitting.

1. Install a new retaining ring into the quick connect fitting using the following procedure
2. Hook one of the open ends of the retaining ring in one of the slots in the quick connect fitting.
3. Rotate the retaining ring around the fitting until the retaining ring is positioned with all 3 ears through the 3 slots on the fitting.
4. Do not install the new retaining ring onto the fitting by pushing the retaining ring.
5. Ensure that the 3 retaining ring ears are seen from inside the fitting and that the retaining ring moves freely in the fitting slots.
6. Install the cooler line into the quick connect fitting.
7. Insert the cooler line end into the quick connect fitting until a click is either heard or felt.
8. Do not use the plastic cap on the cooler line in order to install the cooler line into the fitting.
9. Pull back sharply on the cooler line in order to ensure that the cooler line is fastened into the quick connect fitting.
10. Position (snap) the plastic cap onto the fitting. Do not manually depress the retaining ring when installing the plastic cap onto the quick connect fitting.
11. Ensure that the plastic cap is fully seated against the fitting.
12. Ensure that no gap is present between the cap and the fitting.
13. Ensure that the yellow identification band on the tube is hidden within the quick connect fitting.
14. A hidden yellow identification band indicates proper joint seating.
15. Fill the transmission to the proper level with DEXRON® VI transmission fluid. Refer to «Transmission Fluid Level and Condition Check»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-6l90-myd-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .

1. Remove the upper oil cooler line from the radiator.
2. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/express-g2500/2013-2013/remont/hoistjack/#general-information) .
3. If equipped with AWD, remove the engine protector shield. Refer to «Engine Protection Shield Replacement»(/chevrolet/express-g2500/2013-2013/remont/frames-subframes-crossmembers/#frame-and-underbody) .
4. Remove the lower cooler line from the radiator.
5. Pull the plastic cap back from the quick connect fitting and down along the cooler line about two inches.
6. Using a bent-tip screwdriver, pull on one of the open ends of the retaining ring in order to rotate the retaining ring around the quick connect fitting until the retaining ring is out of position and can be completely removed.
7. Remove the retaining ring from the quick connect fitting.
8. Discard the retaining ring.
9. Pull the cooler line straight out from the quick connect fitting.
10. Remove the retaining ring (E-clips) securing the cooler line to the quick connect in order to remove the remaining cooler lines from the remaining quick connect fittings.
11. Remove the cooler lines from the retaining clip at the oil pan.
12. Remove the cooler lines from the vehicle.

1. Install a new retaining ring (E-clip) into the quick connect fitting using the following procedure
2. Hook one of the open ends of the retaining ring in one of the slots in the quick connect fitting.
3. Rotate the retaining ring around the fitting until the retaining ring is positioned with all three ears through the three slots on the fitting.
4. Do not install the new retaining ring onto the fitting by pushing the retaining ring.
5. Ensure that the three retaining ring ears are seen from inside the fitting and that the retaining ring moves freely in the fitting slots.
6. Install the new retaining ring (E-clip) into the remaining quick connect fittings.
7. Install the cooler lines to the vehicle.
8. Install the cooler lines into the quick connect fittings.
9. Insert the cooler line end into the quick connect fitting until a click is either heard or felt.
10. Do not use the plastic cap on the cooler line in order to install the cooler line into the fitting.
11. Pull back sharply on the cooler line in order to ensure that the cooler line is fastened into the quick connect fitting.
12. Position (snap) the plastic cap onto the fitting. Do not manually depress the retaining ring when installing the plastic cap onto the quick connect fitting.
13. Ensure that the plastic cap is fully seated against the fitting.
14. Ensure that no gap is present between the cap and the fitting.
15. Ensure that the yellow identification band on the tube is hidden within the quick connect fitting. A hidden yellow identification band indicates proper joint seating.
16. Do not install the cooler line end into the fitting incorrectly.
17. If you cannot position the plastic cap against the fitting, remove the retaining ring from the quick connect fitting per Step 5 of the cooler line removal procedure. Check the retaining ring and the tube end in order to ensure neither is bent. Replace the cooler line or the retaining ring if necessary, and reinstall per step 2 of the cooler line installation procedure.
18. Install the cooler lines into the retaining clip at the oil pan.
19. Install the flair nut securing the lower oil cooler line to the radiator and tighten to 45 N.m (33 lb ft).
20. Lower the vehicle.
21. Install the flare nut securing the upper cooler line to the radiator and tighten to 45 N.m (33 lb ft).
22. Start the engine.

1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/express-g2500/2013-2013/remont/hoistjack/#general-information) .
2. Remove the transmission fluid cooler hose from the radiator. Refer to «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Disconnection and Connection (4L60-E/4L65-E/4L70-E)»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-cooling-system) , «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Disconnection and Connection (6L45/6L50/6L80/6L90)»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-cooling-system) .
3. Remove the transmission cooling line bracket retaining bolt (2).
4. Remove the cooling lines from the transmission.
5. Remove the oil cooling lines from the vehicle.

1. Install the transmission oil cooler lines to the vehicle.
2. Install the cooler lines to the transmission.
3. Install the transmission cooler line bracket bolt (2) and tighten to 22 N.m (16 lb ft).
4. Install the transmission fluid cooler hose to the radiator. Refer to «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Disconnection and Connection (4L60-E/4L65-E/4L70-E)»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-cooling-system) , «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Disconnection and Connection (6L45/6L50/6L80/6L90)»(/chevrolet/express-g2500/2013-2013/remont/automatic-trans/#automatic-transmission-cooling-system) .
5. Lower the vehicle.

See also:
• Special Tools
• Grille Replacement (Base)
• Ambient Air Temperature Gauge Sensor Replacement
• Fastener Caution
• Transmission Fluid Level and Condition Check
• Transmission Fluid Level and Condition Check
• Lifting and Jacking the Vehicle
• Engine Protection Shield Replacement
• Transmission Fluid Cooler Hose/Pipe Replacement (4L60-E/4L65-E/4L70-E)