Special Testing Procedure - Automatic Transmission
AUTOMATIC TRANSMISSION SPECIAL TESTING PROCEDUREThe special tests are designed to aid the technician in diagnosing the hydraulic and mechanical portion of the transmission.
Engine Idle Speed Check
See SYMPTOM TROUBLESHOOTING CHART - ENGINE DRIVEABILITY for diagnosis and testing of the engine idle speed.
Line Pressure Test
Caution:
^ Perform Line Pressure Test prior to performing Stall Speed Test. If line pressure is low, do not perform Stall Speed Test or further transmission damage will occur. Do not maintain wide open throttle in any gear range for more than five seconds.
Note:
^ Certain sensor failures may cause high Electronic Pressure Control (EPC), FMEM (Failure Mode Effect Management) actions. Be sure that Self Test and electrical repairs have been performed, or test results may be incorrect.
This test verifies that the line pressure is within specifications.
1. Connect pressure gauge to the line pressure tap.
2. Start engine and check line pressures. Refer to the Pressure chart to determine if line pressure is within specifications.
^ If line pressure is not within specifications, check EPC pressure.
3. Connect Pressure Gauge to EPC pressure tap.
4. Restart engine and check EPC pressure. Refer to Reference pressure chart for specification.
^ If EPC pressure is not within specification, see DTC P1746, P1747: ELECTRONIC PRESSURE CONTROL (EPC) SOLENOID 5R44E AND 5R55E ONLY, to diagnose EPC.
^ If EPC operation is OK, refer to line pressure diagnosis chart for line pressure concern causes.
Stall Speed Test
This test checks operation of the following items:
^ Torque converter clutch
^ Forward clutch
^ Low one way clutch (OWC) assembly
^ Engine performance
Warning:
^ Apply the parking brake firmly while performing each stall test.
Caution:
^ Always perform Line Pressure Test procedures prior to performing the Stall Speed Test. If line pressure is low at stall, do not perform Stall Speed Test or further transmission damage will occur.
Note:
^ The Stall Speed Test should be performed with the engine and transmission at normal operating temperatures.
1. Connect tachometer to the engine.
Caution:
^ After testing each of the following ranges D, 2, 1, and R. move the transmission range selected lever to N (NEUTRAL) and run engine at 1000 rpm for about 15 seconds to allow the torque converter to cool before testing the next range.
Do not maintain wide open throttle in any range for more than five (5) seconds.
If the engine rpm recorded by the tachometer exceeds maximum specified rpm, release the accelerator pedal immediately. Clutch or band slippage is indicated.
2. Press accelerator pedal to floor (WOT) in each range. Record rpm reached in each range. Stall speeds should be as follows:
^ If stall speeds were too high, Refer to the Stall Speed Diagnosis Chart.
^ If stall speeds were too low, first check the engine idle speed.
^ If engine idle is OK, remove torque converter and check the torque converter clutch for slippage.
Note:
^ Prolonged use of this procedure may set Diagnostic Trouble Code P0712, P1783. After performing the Stall Speed Test, run the OBD Test. Clear all DTCs from memory.
Air Pressure Tests
A no-drive condition can exist even with correct transmission fluid pressure because of inoperative clutches or bands. An erratic shift can be located through a series of checks by substituting air pressure for fluid pressure to determine the location of the malfunction.
Follow the procedure to determine the location of the inoperative clutch or band by introducing air pressure into the various test plate passages.
Note:
^ Use only dry, regulated (276 kPa [40 psi] maximum) air pressure.
Apply air to the appropriate passage(s). A dull thud should be felt or heard or movement could be observed when the component applies. There should be no hissing sound when the component is fully applied.
Cover the vent hole in the test plate with a clean, lint-free shop towel to prevent spray when the air is applied. Plugging the vent hole during testing will result in inaccurate results.
1. Drain transmission fluid and remove the oil pan.
2. Remove the control valve body.
3. Install SST 49 UN01 021 and gasket. Tighten bolts to 10 - 12 Nm {102 - 122 kgf-cm, 7.5 - 8.8 ft. lbs.}.
Note:
^ Do not apply air to the test plate vent hole.
4. Apply air to the appropriate clutch port (Refer to diagram). A dull thud may be heard or movement felt when the component is applied or released.
^ If clutch seals or check balls are leaking, a hissing sound may be heard.
^ If test results find that the servos do not operate, disassemble, clean and inspect them to locate the source of the concern.
^ If air pressure applied to the clutch passages fails to operate a clutch, or operates another clutch simultaneously, disassemble and use air pressure to check the fluid passages in the center support and clutches to detect obstructions.
Leakage Inspection
Caution:
^ Do not try to stop the fluid leak by increasing the torque beyond specifications This may cause damage to the case threads.
Leakage at the oil pan to case gasket often can be stopped by tightening the attaching bolts to 13 - 15 Nm {133 - 153 kgf-cm, 115 - 133 inch lbs.}. If necessary, Replace the oil pan case gasket.
1. Check the fluid filler tube connection at the transmission case.
^ If leakage is found here, install a new grommet.
2. Check fluid lines and fittings between the transmission and the cooler in the radiator tank for looseness, wear, or damage.
^ If leakage cannot be stopped by tightening a fluid tube nut, replace the damaged parts.
^ When fluid is found leaking between the case and cooler line fitting, check for missing or damaged O-ring, then tighten the fitting to maximum specification.
^ If the leak continues, replace cooler line fitting and tighten to specification. The same procedure should be followed for fluid leaks between the radiator cooler and the cooler line fittings.
3. Check for engine coolant in the radiator.
^ If transmission fluid is present in the coolant, the cooler in the radiator is probably leaking.
4. The cooler can be further checked for leaks by disconnecting the lines for the cooler fittings and applying no more than 345 kPa (50 psi) air pressure to the fittings. Remove the radiator cap to relieve the pressure buildup at the exterior of the oil cooler tank.
^ If the cooler is leaking and/or will not hold pressure, replace the cooler.
5. If leakage is found at the transmission range selector lever, replace the seal.
6. If leakage is found at the transmission internal harness connector, replace O-ring.
External Sealing
The transmission has the following parts to prevent external fluid leakage:
^ gaskets
^ Lip-type seals
^ O-ring seals
^ seal rings
^ seal grommets
^ thread sealant
Fluid Leakage in Torque Converter Area
In diagnosing and correcting fluid leaks in the front pump support and gear and torque converter area, use the following procedures to locate the exact cause of the leakage. Leakage at the front of transmission, as evidenced by fluid around the torque converter housing, may have several sources. By careful observation, it is possible, in many instances, to pinpoint the source of leak before removing the transmission from the vehicle. The paths which the fluid takes to reach the bottom of the torque converter housing are shown in the illustration. The five steps following correspond with the numbers in the illustration.
Transmission Side
1. Fluid leaking by the front pump seal lip will tend to move along the impeller hub and onto the back of the impeller housing. Except in the case of a total seal failure, fluid leakage by the lip of the seal will be deposited on the inside of the torque converter housing only near the outside diameter of the housing.
2. Fluid leakage by the outside diameter of the front pump seal and front pump body will follow the same path that leaks by the inside diameter of the front pump seal follow.
3. Fluid that leaks by a front pump to case bolt or pump gasket will be deposited on the inside of the torque converter housing only. Fluid will not be deposited on the back of the torque converter.
4. Fluid leakage from the converter drain plug, (model dependent) converter seal weld or converter to flywheel stud weld will appear at the outside diameter of the torque converter on the back face of the flywheel, and in the converter housing only near the flywheel. Fluid leaks from the torque converter will leave a ring of fluid around the inside of the torque converter housing.
Note:
^ White facial tissue paper may aid in determining the color (red is transmission fluid) and source of the leaking fluid.
Engine Side
5. Engine oil leaks are sometimes improperly diagnosed as transmission pump gasket leaks. The following areas of possible leakage should also be checked to determine if engine oil leakage is causing the concern.
a. Leakage at the valve cover gasket may allow oil to flow over the torque converter housing or seep down between the torque converter housing and cylinder block, causing oil to be present in or at the bottom of the torque converter housing.
b. Oil galley plug leaks will allow oil to flow down the rear face of the cylinder block to the bottom of the torque converter housing.
c. Leakage at the crankshaft rear oil seal will work back to the flywheel, and then into the torque converter housing.
d. Leakage at oil pressure sensor.
Leak Check Test
1. Remove the fluid level indicator and note the color of the fluid. Original factory automatic transmission fluid is dyed red to aid in determining if leakage is from the engine or transmission. Unless a considerable amount of makeup fluid has been added or the fluid has been changed, the red color should assist in pinpointing the leak.
2. Remove the torque converter housing cover. Clean off any fluid from the top and bottom of the torque converter housing, front of the case and rear face of the engine and oil pan. Clean the torque converter area by washing with a suitable nonflammable solvent and blow dry with compressed air.
3. Wash out the torque converter housing, the front of the flywheel and the converter drain plugs. The torque converter housing may be washed out using cleaning solvent and a squirt-type oil can. Blow all washed areas dry with compressed air.
4. Start and run the engine until the transmission reaches its normal operating temperature. Observe the back of the cylinder block and top of the torque converter housing for evidence of fluid leakage.
5. Raise the vehicle on a hoist and run the engine at fast idle, then at engine idle, occasionally shifting to the Overdrive and Reverse ranges to increase pressure within the transmission. Observe the front of the flywheel, back of the cylinder block (in as far as possible), and inside the torque converter housing and front of the case. Run the engine until fluid leakage is evident and the probable source of leakage can be determined.
Leak Check Test With Black Light
Fluid soluble aniline or fluorescent dyes premised at the rate of 2.5ml (1/2 teaspoon) of dye powder to 0.24L (1/2 pint) of automatic transmission fluid have proven helpful in locating the source of fluid leakage. Such dyes may be used to determine whether an engine fluid or transmission fluid leak is present, or if the fluid in the transmission fluid cooler hose leaks into the engine coolant system. An ultraviolet light must be used to detect the fluorescent dye solution.
Transmission Fluid Cooler
Caution:
^ Whenever a transmission has been disassembled to replace worn or damaged parts or because the main control valve body sticks from foreign material, the main control valve body, transmission fluid cooler and fluid cooler inlet tube and fluid cooler tube must be cleaned and flushed using Torque Converter/Oil Cooler Cleaner. Under no circumstances should an attempt be made to clean the torque converter by hand agitation with solvent.
When internal wear or damage has occurred in the transmission, metal particles, clutch plate material, or band material may have been carried into the torque converter and transmission fluid cooler. These contaminants are a major cause of recurring transmission troubles and must be removed from the system before the transmission is put back into use.
Transmission Fluid Cooler Flow Test
Note:
^ The transmission linkage/cable adjustment, fluid level and line pressure must be within specification before performing this test.
1. Remove fluid level indicator from fluid filler tube.
2. Place funnel in fluid filler tube.
3. Raise the vehicle on a hoist and place suitable safety stands under the vehicle.
4. Remove the cooler return line (rear fitting) from the fitting on the transmission case.
5. Connect one end of a hose to the cooler return line and route other end of the hose up to a point where it can be inserted into the funnel at the fluid filler tube.
6. Remove the safety stands and lower the vehicle. Insert end of hose into the funnel.
7. Start the engine and run it at idle with the transmission in NEUTRAL position.
8. When fluid flowing from hose is in a steady stream, a liberal amount of fluid should be observed. "Liberal" is described as about 1 liter (1 qt) delivered in 30 seconds. If a liberal flow is observed, the test is complete.
^ If the flow is not liberal, stop the engine. Disconnect the hose from the cooler return line and connect it to the converter outlet fitting (front fitting) on the transmission case.
9. Repeat Steps 7 and 8.
^ If flow is now approximately 1 liter (1 quart) in 30 seconds, refer to cleaning and back flushing procedures.
^ If the flow is still not approximately 1 liter (1 quart) in 30 seconds, service the pump and/or torque converter.