The 4R44E/4R55E uses a four element torque converter. The converter contains the standard internal components (turbine, impeller, and stator) for transfer of power and multiplication of torque. It also utilizes a disc type Torque Converter Clutch (TCC) for maximum fuel economy.
The operation of the main torque converter components is as follows:
- The converter cover and impeller are connected to the engine crankshaft. Rotation of the cover and impeller by the engine crankshaft sets the fluid in motion.
- The turbine reacts to the fluid motion from the impeller, transferring rotation to the geartrain by way of the turbine shaft.
- The stator redirects the fluid going back to the impeller, from the turbine. By directing fluid back to the impeller in the same direction as engine rotation, the stator multiplies engine torque.
When applied, the TCC provides a mechanical link between the converter turbine and the engine, allowing for a direct mechanical power transfer from the engine to the transmission. The converter clutch pressure plate is applied and released by fluid pressure, which is controlled by the Powertrain Control Module (PCM). The PCM controls the torque converter clutch using a pulse-width modulated TCC solenoid.
Torque Converter Assembly
|1 ||- ||Cover (Part of 7902) |
|2 ||- ||Thrust Washer (Part of 7902) |
|3 ||- ||Converter Damper Plate (Part of 7902) |
|4 ||- ||O-Ring (Part of 7902) |
|5 ||- ||Turbine Assembly (Part of 7902) |
|6 ||- ||Thrust Bearing (Part of 7902) |
|7 ||- ||Thrust Washer (Part of 7902) |
|8 ||- ||Snap Ring (Part of 7902) |
|9 ||- ||Reactor (Part of 7902) |
|10 ||- ||One-Way Clutch Assembly (Part of 7902) |
|11 ||- ||Thrust Washer (Part of 7902) |
|12 ||- ||Thrust Bearing (Part of 7902) |
|13 ||- ||Impeller Assembly (Part of 7902) |
Impeller and Cover
The impeller sets the oil in motion and directs it to the turbine. The impeller is welded to the converter cover.
The turbine is the driven member of the converter. It is driven by oil from the impeller and transfers the hydraulic power to the transmission. When the converter lockup clutch is engaged, the power is transferred mechanically.
The reactor is equipped with heavily curved vanes and its center hub has an one-way clutch which prevents the stator from rotating opposite to the engine rotation. The reactor reverses the oil and returns it to the impeller in the direction of impeller rotation. The one-way clutch prevents the force of this fluid from turning the stator against the impeller and turbine.
Torque Converter Clutch (TCC)
The clutch is joined to the turbine by means of the externally splined hub of the turbine and also internally splines within its own assembly.
When engaged the clutch friction plate bears against the inside of the converter cover. Thereby producing a direct mechanical connection between the pump housing and the turbine.
The reactor one-way clutch is built into the reactor (stator) and prevents it from rotating opposite to engine rotation.
Torque Converter Clutch Operation Test
This test verifies that the torque converter clutch control system and the torque converter are operating properly. Perform the test as follows:
- Connect tachometer to engine.
- Bring engine to normal operating temperature by driving vehicle at highway speeds for approximately 15 minutes in (D) range.
- After normal operating temperatures are reached, maintain constant vehicle speed of about 80 km/h (50 mph). Release throttle for about two seconds then reapply throttle to previous setting.
- Engine rpm should increase when throttle is released and decrease in about five seconds (converter engagement) after throttle is reapplied. If this does not occur, refer to Torque Converter Operation Concerns on the Diagnosis by Symptom Index.
3. Visual Inspection
- Vehicle modification
- Electronic add-on items
- Air conditioning
- Generators (alternators)
- Engine turbos
- Cellular telephones
- Cruise controls
- CB radios
- Linear boosters
- Backup alarm signals
- Leaks - Refer to Special Testing section.
- Proper linkage adjustments - Refer to Section 07-05.
- These items, if not installed properly, will affect powertrain control module or transmission function. Pay particular attention to add-on wiring splices in the powertrain control module harness or transmission wiring harness, abnormal tire size, or axle ratio changes.
- After a road test, with the vehicle warm and before disturbing any connectors, perform the Quick Test using Rotunda Super Star II Tester(NNN) NNN-NNNN or New Generation Star (NGS) Tester (007-00500) or equivalents. Refer to the Powertrain Control/Emissions Diagnosis Manual, Explorer (OBDI) or Ranger (OBDII).
4. Check Technical Service Bulletins and Oasis
5. Perform OBD Diagnostic Procedures (KOER, KOEO