Diagnosis And Testing

AUTOMATIC TRANSMISSION 

Transmission malfunctions may be caused by these general conditions:

• Poor engine performance
• Improper adjustments
• Hydraulic malfunctions
• Mechanical malfunctions
• Electronic malfunctions
• Incorrect Torque Converter Clutch (TCC) solenoid PI curve

Diagnosis of these problems should always begin by checking the easily accessible variables: fluid level and condition, gearshift cable adjustment. Then perform a road test to determine if the problem has been corrected or if more diagnosis is necessary. If the problem persists after the preliminary tests and corrections are completed, hydraulic pressure checks should be performed.

FLUID LEAKAGE 

TRANSMISSION OIL LEAK 

Begin with a thorough inspection of the transmission, particularly at the area of the suspected leak. If an oil leak source is not readily identifiable, the following steps should be followed:

1. Clean or degrease the transmission with a water soluble solvent only.
2. Add an oil soluble dye (use as recommended by manufacturer) while the powertrain is at ambient temperature. Start the engine and let idle for approximately 15 minutes. Check the oil dip stick (if equipped) to make sure the dye is thoroughly mixed as indicated with a fluorescent color under a black light.
3. Using a black light, inspect the entire transmission for fluorescent dye, practically at the suspected area of oil leak. If the oil leak is found and identified, repair per service information instructions.
4. If dye is not observed, drive the vehicle at various speeds for approximately 24 km (15 miles) and repeat inspection.

TORQUE CONVERTER HOUSING AREA 

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1 - PUMP SEAL

2 - PUMP VENT

3 - PUMP BOLT

4 - PUMP GASKET

5 - CONVERTER HOUSING

6 - CONVERTER

7 - REAR MAIN SEAL LEAK

When diagnosing converter housing (5) fluid leaks, three actions must be taken before repair:

1. Verify proper transmission fluid level.
2. Verify that the leak originates from the converter housing area and is transmission fluid.
3. Determine the true source of the leak.

Fluid leakage at or around the torque converter area may originate from an engine oil leak (7). The area should be examined closely. Factory fill fluid is red and, therefore, can be distinguished from engine oil.

Some suspected converter housing fluid leaks may not be leaks at all. They may only be the result of residual fluid in the converter housing, or excess fluid spilled during factory fill, or fill after repair. Converter housing leaks have several potential sources. Through careful observation, a leak source can be identified before removing the transmission for repair.

The 68RFE uses a one piece pump cover which includes the impeller hub seal. Leaks at the pump cover o-ring or the impeller hub seal usually travel down the inside of the converter housing.

TORQUE CONVERTER LEAKAGE 

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1 - OUTSIDE DIAMETER WELD

2 - TORQUE CONVERTER HUB WELD

3 - STARTER RING GEAR

4 - LUG

Possible sources of torque converter leakage are:

• Torque converter weld leaks at the outside diameter weld (1).
• Torque converter hub weld (2).

PRELIMINARY 

Two basic procedures are required. One procedure for vehicles that are drivable and an alternate procedure for disabled vehicles (will not back up or move forward).

VEHICLE IS DRIVABLE 

1. Record all DTCs and the accompanying DTC Event Data.
2. Check for an appropriate Technical Service Bulletin that applies to the customer complaint.
3. Check fluid level and condition.
4. Road test and note how transmission upshifts, downshifts, and engages.
5. If the complaint was related to shift quality, perform the Quick Learn procedure,
6. If the shift complaint still exists, compare actual line pressure (sensor reading, using the scan tool) to the Desired Line Pressure reading, in Park, Drive, and Reverse at 1500 RPM. Check that the LP sensor reads 30 psi (the minimum it should ever display) with key on / engine off.
7. Follow the diagnosis procedure for any DTC's that exist.

VEHICLE IS DISABLED 

1. Record all DTCs and the accompanying DTC Event Data.
2. Compare actual line pressure (sensor reading, using the scan tool) to the Desired Line Pressure reading, in Park, Drive, and Reverse at 1500 RPM. Check that the LP sensor reads 30 psi (the minimum it should ever display) with key on / engine off. If line pressure is incorrect, check fluid level and condition.
3. With engine running, place transmission in gear and verify correct PRNDL reading. Observe the Input and Output speeds using the scan tool. If output RPM is greater than zero but vehicle does not move, check for transfer case in Neutral (or failed internally), failed propshaft, or failed / disconnected drive axle. If output RPM is zero and input RPM is greater than zero, internal transmission slippage is indicated. Run clutch slip tests using the scan tool, check oil pan for debris, and air check the various clutch circuits.
4. Shift the transmission into neutral, if both input and output speeds are zero, check flexplate bolts, torque converter, and transmission input shaft.
5. Remove, inspect, and repair the transmission as necessary

ROAD TESTING 

Before road testing, be sure the fluid level and control cable adjustments have been checked and adjusted if necessary. Verify that all DTC's have been resolved.

Observe engine performance during the road test. A poorly tuned engine will not allow accurate analysis of transmission operation.

Operate the transmission in all gear ranges. Check for shift variations and engine flare which indicates slippage. Note if shifts are harsh, spongy, delayed, early, or if part throttle downshifts are sensitive.

Slippage indicated by engine flare, usually means clutch or line pressure problems.

A slipping clutch can often be determined by comparing which internal units are applied in the various gear ranges. The Clutch Application charts provide a basis for analyzing road test results.

GEAR RANGE	UD	OD	R	2C	4C	L/R	OVERRUNNING
P-PARK						ON
R-REVERSE			ON			ON
N-NEUTRAL						ON
D-FIRST	ON					ON*	ON
D-SECOND	ON			ON
D-THIRD (SECOND PRIME)	ON				ON
D-FOURTH	ON	ON
D-FIFTH		ON			ON
D-SIXTH		ON		ON
D-LIMP-IN (FULL)	ON	ON
*L/R clutch is on only with the output shaft speed below 150 rpm.

HYDRAULIC PRESSURE TEST 

An accurate tachometer and pressure test gauges are required. Test Gauge (special tool #C-3293-SP, Gauge, Pressure 0-300 P.S.I.) has a 300 psi range and is used at all locations where pressures exceed 100 psi.

PRESSURE TEST PORT LOCATIONS 

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1 - TCC RELEASE

2 - TO COOLER

3 - TCC APPLY

4 - FROM COOLER

5 - LINE PRESSURE SENSOR

Only two pressure ports are supplied on the transmission case. The torque converter clutch apply (3) and release (1) ports are located on the right side of the transmission case .

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1 - LINE PRESSURE SENSOR PORT

2 - LINE PRESSURE SENSOR

3 - TOOL 8259

4 - PRESSURE TAP

To determine the line pressure, there are two available methods. The scan tool can be used to read line pressure from the line pressure sensor. The second method is to install Line Pressure Adapter (special tool #8259, Adapter, Pressure Test) (3) into the transmission case and then install the pressure gauge and the original sensor (2) into the adapter. This will allow a comparison of the scan tool readings and the gauge reading to determine the accuracy of the line pressure sensor. The scan tool line pressure reading should match the gauge reading within ±10 psi.

TEST PROCEDURE 

All pressure readings should be taken with the transmission fluid level full, transmission oil at the normal operating temperature, and the engine at 1500 rpm. Check the transmission for proper operation in each gear position that is in question or if a specific element is in question, check the pressure readings in at least two gear positions that employ that element. Refer to SCHEMATICS AND DIAGRAMS  to determine the correct pressures for each element in a given gear position.

Some common pressures that can be measured to evaluate pump and clutch performance are the upshift/downshift pressures, garage shift pressures, and TCC pressure. The upshift/downshift pressure for all shifts are shown in the tables below. Refer to UPSHIFT PRESSURES  and DOWNSHIFT PRESSURES . In-gear maximum pressure for each gear position is shown in table. Refer to IN-GEAR PRESSURES .

68RFE
ENGINE	1-2	2-3	3-4	4-5	5-6	2-4	3-5	4-6
6.7L	160	150	150	160	160	150	150	160

68RFE
ENGINE	6-5	6-4	5-4	5-3	4-3	4-2	3-2	3-1	2-1	-
6.7L	150	150	150	160	150	160	150	160	160	-

68RFE
ENGINE	1	2	3	4	5	6	NEUTRAL	REVERSE
6.7L	160	150	150	160	160	160	125	250

Actual line-pressure while in-gear will vary based upon minimum learned line-pressure. Minimum line-pressure starts at 40 psi and learns up to the minimum pressure to hold the clutches in a applied state.

AIR CHECKING TRANSMISSION CLUTCH OPERATION 

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1 - LOW REVERSE CLUTCH

2 - 4C CLUTCH

3 - 2C CLUTCH

4 - OVERDRIVE CLUTCH

5 - UNDERDRIVE CLUTCH

6 - REVERSE CLUTCH

Air-pressure testing can be used to check transmission clutch operation. The test can be conducted with the transmission either in the vehicle or on the work bench, as a final check.

Air-pressure testing requires that the oil pan and valve body be removed from the transmission. The clutch apply passages are shown above in the Air Pressure Test Passages graphic.

Apply air pressure at each port. If the clutch is functioning, a soft thump will be heard as the clutch is applied. The clutch application can also be felt by touching the appropriate element while applying air pressure. As the air pressure is released, the clutch should also release.

CONVERTER HOUSING FLUID LEAK 

When diagnosing converter housing fluid leaks, two items must be established before repair.

1. Verify that a leak condition actually exists.
2. Determined the true source of the leak.

Some suspected converter housing fluid leaks may not be leaks at all. They may only be the result of residual fluid in the converter housing, or excess fluid spilled during factory fill or fill after repair. Converter housing leaks have several potential sources. Through careful observation, a leak source can be identified before removing the transmission for repair. Torque converter seal leaks tend to move along the drive hub and onto the rear of the converter. Pump cover seal leaks tend to run down the cover and the inside surface of the bellhousing.

Some leaks, or suspected leaks, may be particularly difficult to locate. If necessary, a Mopar® approved dye should be used to locate and confirm a leak.

TORQUE CONVERTER LEAK POINTS 

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1 - TURBINE ASSEMBLY

2 - STATOR

3 - CONVERTER HUB

4 - O-RING

5 - IMPELLER ASSEMBLY

6 - CONVERTER CLUTCH PISTON

7 - TURBINE HUB

Possible sources of converter leaks are:

1. Leaks at the weld joint around the outside diameter weld.
2. Leaks at the converter hub weld.

In most cases, a torque converter which is wet from transmission fluid indicates a leak at one of these areas.