Torque Converter
Several torque converters are available to match the transmissions to a wide variety of diesel and gasoline engines. The torque converter is a single-stage, polyphase, and three-element unit, consisting of a pump, stator, and turbine. At lower output speeds, the torque converter multiplies torque and provides a fluid coupling to the engine. At higher speeds, the Torque Converter Clutch (TCC) is automatically engaged to provide direct drive from the engine to the transmission. Hydraulic fluid for converter charging pressure comes from the sump and is supplied by the input pump. The torque converter clutch is applied or released by changing direction of fluid in the torque converter. An integral converter damper minimizes the need for additional engine vibration control.
Throttle Position/Torque Management
The TCM receives input on throttle position/torque management from a signal transmitted by the engine electronic controls.
The engine electronic controls communicate directly to the transmission electronic controls over an SAE J1850 or J1939 Serial Communication Interface (SCI) data link. The transmission TCM must be calibrated to receive these signals.
Upshift Control & Torque Converter Clutch Apply
The TCM calculates the upshift points based on throttle angle and the engine, turbine and output speed. When the TCM determines that conditions are met for a shift to occur, the TCM commands the shift and controls solenoid "A" and "B" current to properly control clutch pressures during the shift.
- Choose a throttle angle of 10, 25 or 50 percent. All throttle angles shown should be tested to cover the normal driving range.
- Monitor the following scan tool parameters: Throttle Angle Vehicle Speed Engine Speed Output Shaft Speed Commanded Gear Slip Speed Solenoid States
- Place the gearshift lever in the Drive position.
- Accelerate the vehicle using the chosen throttle angle. Hold the throttle steady.
- As the transmission upshifts, note the vehicle speed when the shift occurs for each gear change. There should be a noticeable shift feel or engine speed change within 1-2 seconds of the commanded gear change.
- Compare the shift speeds to the shift speed chart. Shift speeds may vary slightly due to transmission fluid temperature or hydraulic delays in responding to electronic controls. Note any harsh, soft or delayed shifts or slipping. Note any noise or vibration.
- Repeat steps 1 - 6 to complete all throttle angles.
- Check for TCC apply in 2nd, 3rd, 4th and 5th gear. Note the TCC apply point. When the TCC applies, there should be a noticeable drop in engine speed and a drop in slip speed to below 100 RPM. If the TCC apply can not be detected, check for DTCs. Lightly tap and release the brake pedal. The TCC will release.
SHIFT SPEED SPECIFICATIONS
Note. Manufacturer does not provide shift speed specifications for 2001 models. For 2002 models (Scheme 210)and (Scheme 211).
Scheme 210
Scheme 211
TORQUE CONVERTER DIAGNOSIS
The Torque Converter Clutch (TCC) is applied by fluid pressure, which is controlled by a PWM solenoid valve. This solenoid valve is located inside of the automatic transmission assembly. The solenoid valve is controlled through a combination of computer controlled switches and sensors.
Torque Converter Stator
The torque converter stator roller clutch can have two different malfunctions.
- The stator assembly freewheels in both directions.
- The stator assembly remains locked up at all times.
Torque Converter Clutch Shudder
The key to diagnosing Torque Converter Clutch (TCC) shudder is to note when it happens and under what conditions.
TCC shudder which is caused by the transmission should only occur during the apply or the release of the converter clutch. Shudder should never occur after the TCC plate is fully applied.
If the shudder occurs while the TCC is applying, the problem can be within the transmission or the torque converter. Something is causing one of the following conditions to occur
- Something is not allowing the clutch to become fully engaged.
- Something is not allowing the clutch to release.
- The clutch is releasing and applying at the same time.
One of the following conditions may be causing the condition to occur
- Leaking turbine shaft seals.
- A restricted release orifice.
- Defective friction material on the TCC piston.
TORQUE SPECIFICATIONS
| Application | Ft. Lbs. (N.m) |
|---|---|
| Control Lever Nut | 18 (25) |
| PNP Switch Bolt | 20 (27) |
| INCH Lbs. (N.m) | |
| Line Pressure Plug | 106 (12) |
| PCM Connector End Bolt | 71 (8) |
| Speed Sensor Bolt | 106 (12) |
| TCM Cover Bolt | 80 (9) |
TORQUE SPECIFICATIONS
