Troubleshooting the automatic transmission is simplified by using the proven method of diagnosis. One of the most important things to remember is that there is a definite procedure to follow. Do not take short cuts or assume that critical checks or adjustments have already been made.

The following procedures are recommended for checking and/or verifying that the various components are adjusted and operating properly. Use Rotunda Automatic Transmission Tester 014-00737 or equivalent. Follow the manufacturer's instructions.

Control Pressures Test

Line pressure and throttle pressure on the Automatic Overdrive transmission are tested in the idle position (zero TV) and wide-open throttle position. In each of the two modes, the reverse specifications will be higher than the others.

Control pressure specifications can be found in the Special Specifications booklet.

1. Be sure the TV linkage is properly adjusted.

2. Connect a 2000 kPa (300 psi) gauge to the main line pressure tap on the case LH side just above the control levers. Have sufficient flexible hose to make the gauge accessible while operating the engine.

    CAUTION: Pressure gauges affect the shift quality of the transmission. Care should be taken not to accelerate or decelerate rapidly. Possible transmission failure could result.

   NOTE: WOT readings are to be made at full stall. However, be sure to run the engine at fast idle in NEUTRAL for cooling between tests.

3. Connect a 0-690 kPa (0-100 psi) pressure gauge to the TV pressure tap on the RH side of the case. Have sufficient flexible hose to make the gauge accessible while operating the engine.
   
   
   
   

4. Run the engine until it is hot.

    CAUTION: Idle pressure must be read with the throttle off the fast idle cam.

5. Apply the service and parking brakes firmly and shift through all the ranges. Record the line pressure and throttle pressure and compare it with specifications.

   After making the control pressure tests, analyze the results related to the conditions in the following charts.

   Keep in mind that clutch and servo leakage may or may not show up on the control pressure test. This is because the pump has a high output volume and the leak may not be severe enough to cause a pressure drop; and orifices between the pump and pressure chamber may maintain pressure at the source, even with a leak downstream. Pressure loss caused by a less than major leak is more likely to show up at idle than at WOT where the pump is delivering full volume.

   Conversely, when manipulating the TV linkage to simulate WOT, but actually testing at idle, the leak is more likely to cause a pressure loss in the WOT position.

   To further isolate leakage in a clutch or servo circuit, it is necessary to remove the oil pan and valve body and to perform case air pressure tests.
   
   

   Control Pressures Condition	Possible Cause(s)
   Low in P	Valve body bolts loose, main oil regulator valve sticking, low reverse servo leakage.
   Low in R	Reverse clutch leakage, low reverse servo leakage. Valve body bolts loose.
   Low in N	Valve body bolts loose, main oil regulator valve sticking.
   Low in (D)	Forward clutch leakage, overdrive servo leakage, valve body bolts loose, main oil regulator valve sticking.
   Low in D	Forward clutch leakage, overdrive servo leakage, valve body bolts loose, main regulator valve sticking.
   Low in 1	Forward clutch leakage. Low/reverse servo leakage. Overdrive servo leakage.
   Low at idle in all ranges	Low fluid level, restricted oil filter, loose valve body bolts, pump leakage, case leakage, valve body leakage, excessively low engine idle, fluid too hot, main oil regulator valve sticking.
   High at idle in all ranges	TV linkage, valve body (throttle valve or main oil regulator valve sticking)
   OK at idle but low at WOT	Internal leakage, pump leakage, restricted inlet screen, TV linkage, valve body (TV or TV limit valve sticking, main oil regulator valve sticking).

   
   
   
   

   TV PRESSURE	LINE PRESSURE	RANGE	POSSIBLE CAUSE
   High at WOT	High at WOT	All	TV limit valve not regulating pressure. Replace valve body.
   Low at WOT	Low at WOT	All	Throttle valve stuck. Replace valve body. TV linkage out of adjustment/damaged/binding. Adjust and/or service as necessary.

   
   
   
   
   
   

Direct Clutch Pressure Test

 CAUTION: Pressure gauges affect the shift quality of the transmission. Care should be taken not to accelerate or decelerate rapidly. Possible transmission failure could result.

The direct clutch pressure test outlined below will diagnose a low-pressure condition or leakage in the direct clutch circuit. A difference of 103 kPa (15 psi) or more between direct clutch pressure and line pressure (read at the forward clutch pressure tap) will prevent a normal 3-4 shift.

1. Attach 0-2000 kPa (0-300 psi) pressure gauges to the forward clutch pressure tap and to the direct clutch pressure tap. Gauges must be accurate enough to distinguish a 103 kPa (15 psi) difference. (If this test is done in conjunction with a control pressure test, pressure gauges will be attached to all pressure taps.) Have sufficient flexible hose to read the gauges in the vehicle.

2. Drive the vehicle. When pressure is applied to the direct clutch, note the difference between the pressure read at forward clutch pressure tap and the direct clutch pressure.

3. If the difference in pressures is less than 103 kPa (15 psi), the direct clutch circuit is OK.

4. If the difference is greater than 103 kPa (15 psi),there could be a leak in the direct clutch pressure circuit. If the difference does not exceed 103 kPa (15 psi), the gauges on the line pressure and direct clutch pressure can be switched to confirm that gauge calibration difference is not the cause.