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E4OD Torque Converter
IF THE IMAGE IS TOO SMALL, click it.
A torque converter (7902) couples the engine to the transmission gearset via the input shaft (7017) and the torque converter impeller hub. The impeller hub provides engine rpm to the positive displacement pump. The flow from the pump is proportional to engine rpm, and excess pump capacity is exhausted back to the pump inlet. The input shaft transfers power into the transmission gearset. The power input is controlled by the application of the torque converter clutch, which is scheduled through the powertrain control module. The application of the piston plate effectively replaces the hydraulic coupling between the converter cover and the turbine with a mechanical coupling between the converter cover and the turbine hub. This mechanical coupling helps improve fuel economy and wide-open throttle performance by eliminating converter slip.
The torque converter (7902) is a four-element converter. It contains the standard three elements that transmit and multiply torque:
- Impeller.
- Turbine.
- Reactor.
- Torque converter clutch.
The torque converter clutch increases fuel economy in 3rd and 4th gears.
E4OD & early 4R100 (up to early '99 w/o OSS&TSS) on-off TCC solenoid ~20-30 Ohms
Late '99-up 4R100 (w/OSS&TSS) PWM TCC solenoid ~5 Ohms
The operation of the torque converter components is as follows:
- Rotation of the converter housing and impeller set the fluid in motion.
- The turbine reacts to the fluid motion from the impeller, transferring rotation to the geartrain.
- The reactor redirects fluid going back into the impeller, allowing for torque multiplication.
The addition of a torque converter clutch to the torque converter provides a mechanical link between the converter housing and the engine, allowing for direct transfer of power from the engine to the geartrain. The torque converter clutch is applied and released by fluid pressure, which is controlled by the powertrain control module (PCM) (12A650) through a torque converter clutch solenoid (TCC solenoid) (7G136) in the main control valve body (7A100).
Impeller and Cover
The primary functions of the impeller and cover assembly are to drive the impeller blades, contain hydraulic fluid and provide a mating surface for the converter clutch pressure plate. In addition, the impeller hub drives the fluid pump gear.
Turbine
The turbine is a sectioned, donut-shaped steel stamping that is splined to the input shaft. It is driven by fluid from the impeller and transmits this power to the geartrain. Because of its basic shape, the turbine automatically directs fluid back to the impeller.
Reactor
The reactor redirects the fluid flow returned to the impeller from the turbine so that the fluid moves in the same direction as engine/impeller rotation. This action aids in torque multiplication because it adds torque to that already supplied by the engine. The reactor contains a one-way clutch that holds it stationary when torque multiplication is necessary, but allows freewheeling at higher speeds when torque multiplication is not necessary.
Torque Converter Clutch
The pressure plate attaches to the back of the turbine and can be applied against the cover to allow for a mechanical transfer of engine torque to the geartrain. This occurs mainly in third and fourth gears when torque multiplication is no longer necessary. (Converter clutch application may also occur in second gear under certain conditions.) The pressure plate works much like a regular mechanical clutch. Apply, release and controlled slip of the clutch are controlled by opposing fluid forces on each side of the pressure plate.
Torque converter clutch solenoid (TCC solenoid) (7G136) provides torque converter clutch control by shifting the converter clutch control valve to apply or release the torque converter clutch.
Symptoms: Failed on -- Engine stalls in drive at idle low speeds with brake applied or manual 2. Failed off -- Converter clutch never engages. May flash transmission control indicator lamp.
1. Connect a tachometer to the engine.
2. Bring engine to normal operating temperature by driving the vehicle at highway speeds for approximately 15 minutes in (D) range.
3. After normal operating temperatures are reached, maintain a constant vehicle speed of about 80 km/h (50 mph), and tap the brake pedal with the left foot.
4. Engine rpm should increase when the brake pedal is tapped, and decrease about five seconds after the brake pedal is released. If this does not occur, diagnose Torque Converter.
5. If the vehicle stalls in (D) at idle with the vehicle at a stop, move the gearshift selector lever to the manual 1 position. If the vehicle stalls, the cause may be the converter control valve in the pump. If the vehicle doesn't stall in manual 1, refer to the Electrical Diagnosis.
Stall Speed Test
NOTE: The stall test should only be performed with the engine and transmission at normal operating temperatures. The stall test checks the operation of the following items:
- Torque converter one-way clutch
- Forward clutch
- Low/reverse one-way clutch
- Reverse clutch (7B164)
- Overdrive one-way clutch
- Direct clutch
- Engine performance
WARNING: APPLY THE SERVICE AND PARKING BRAKES FIRMLY WHILE PERFORMING EACH STALL TEST.
CAUTION: Perform line pressure test prior to performing stall test. If line pressure is low at stall, do not perform stall test or further transmission damage will occur.
1. Connect tachometer to engine. CAUTION: Do not maintain Wide Open Throttle (WOT) in any gear range for more than five seconds.
2. After testing each of the following ranges, (D), 2, 1 and R, move gearshift selector lever to N (neutral) and run engine for about 15 seconds to allow torque converter to cool before testing next range. Press accelerator pedal to floor (WOT) in each range. Record rpm reached in each range. Stall speeds should be in appropriate range.
CAUTION: If engine rpm recorded by the tachometer exceeds maximum specified rpm, release accelerator pedal immediately. Clutch or band slippage is indicated.
Engine - - - - Stall Speed (RPM)
. . . 4.9L . . . . . . . . . . . . 1485-1860
. . . 5.0L . . . . . . . . . . . . 1955-2435
. . . 5.8L . . . . . . . . . . . . 2100-2600
. . . 7.3L-D . . . . . . . . . . . 1680-2100
. . . 7.5L . . . . . . . . . . . . 1840-2300
If the stall speeds were too high, refer to the following Stall Speed Diagnosis Chart. If the stall speeds were too low, first check engine tune-up. If engine is OK, remove torque converter and check torque converter reactor one-way clutch for slippage.
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