# Automatic Transmission

## Understanding the Automatic Transmission

The automatic transmission allows engine torque and power to be transmitted to the rear wheels within a narrow range of engine operating speeds. It will allow the engine to turn fast enough to produce plenty of power and torque at very low speeds, while keeping it at a sensible rpm at high vehicle speeds (and it does this job without driver assistance). The transmission uses a light fluid as the medium for the transmission of power. This fluid also works in the operation of various hydraulic control circuits and as a lubricant. Because the transmission fluid performs all of these functions, trouble within the unit can easily travel from one part to another. For this reason, and because of the complexity and unusual operating principles of the transmission, a very sound understanding of the basic principles of operation will simplify troubleshooting.

### TORQUE CONVERTER

The torque converter replaces the conventional clutch. It has three functions:

1. It allows the engine to idle with the vehicle at a standstill, even with the transmission in gear.
2. It allows the transmission to shift from range-to-range smoothly, without requiring that the driver close the throttle during the shift.
3. It multiplies engine torque to an increasing extent as vehicle speed drops and throttle opening is increased. This has the effect of making the transmission more responsive and reduces the amount of shifting required.

The torque converter is a metal case which is shaped like a sphere that has been flattened on opposite sides. It is bolted to the rear end of the engine's crankshaft. Generally, the entire metal case rotates at engine speed and serves as the engine's flywheel.

The case contains three sets of blades. One set is attached directly to the case. This set forms the torus or pump. Another set is directly connected to the output shaft, and forms the turbine. The third set is mounted on a hub which, in turn, is mounted on a stationary shaft through a one-way clutch. This third set is known as the stator.

A pump, which is driven by the converter hub at engine speed, keeps the torque converter full of transmission fluid at all times. Fluid flows continuously through the unit to provide cooling.

Under low speed acceleration, the torque converter functions as follows:

The torque converter housing is rotated by the engine's crankshaft, and turns the impeller. The impeller then spins the turbine, which gives motion to the turbine shaft, driving the gears

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The torus is turning faster than the turbine. It picks up fluid at the center of the converter and, through centrifugal force, slings it outward. Since the outer edge of the converter moves faster than the portions at the center, the fluid picks up speed.

The fluid then enters the outer edge of the turbine blades. It then travels back toward the center of the converter case along the turbine blades. In impinging upon the turbine blades, the fluid loses the energy picked up in the torus.

If the fluid was now returned directly into the torus, both halves of the converter would have to turn at approximately the same speed at all times, and torque input and output would both be the same.

In flowing through the torus and turbine, the fluid picks up two types of flow, or flow in two separate directions. It flows through the turbine blades, and it spins with the engine. The stator, whose blades are stationary when the vehicle is being accelerated at low speeds, converts one type of flow into another. Instead of allowing the fluid to flow straight back into the torus, the stator's curved blades turn the fluid almost 90° toward the direction of rotation of the engine. Thus the fluid does not flow as fast toward the torus, but is already spinning when the torus picks it up. This has the effect of allowing the torus to turn much faster than the turbine. This difference in speed may be compared to the difference in speed between the smaller and larger gears in any gear train. The result is that engine power output is higher, and engine torque is multiplied.

As the speed of the turbine increases, the fluid spins faster and faster in the direction of engine rotation. As a result, the ability of the stator to redirect the fluid flow is reduced. Under cruising conditions, the stator is eventually forced to rotate on its one-way clutch in the direction of engine rotation. Under these conditions, the torque converter begins to behave almost like a solid shaft, with the torus and turbine speeds being almost equal.

### PLANETARY GEARBOX

The ability of the torque converter to multiply engine torque is limited. Also, the unit tends to be more efficient when the turbine is rotating at relatively high speeds. Therefore, a planetary gearbox is used to carry the power output of the turbine to the driveshaft.

Planetary gears work in a similar fashion to manual transmission gears, but are composed of three parts

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Planetary gears function very similarly to conventional transmission gears. However, their construction is different in that three elements make up one gear system, and, in that all three elements are different from one another. The three elements are: an outer gear that is shaped like a hoop, with teeth cut into the inner surface; a sun gear, mounted on a shaft and located at the very center of the outer gear; and a set of three planet gears, held by pins in a ring-like planet carrier, meshing with both the sun gear and the outer gear. Either the outer gear or the sun gear may be held stationary, providing more than one possible torque multiplication factor for each set of gears. Also, if all three gears are forced to rotate at the same speed, the gearset forms, in effect, a solid shaft.

Planetary gears in the maximum reduction (low) range. The ring gear is held and a lower gear ratio is obtained

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Planetary gears in the minimum reduction (drive) range. The ring gear is allowed to revolve, providing a higher gear ratio

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Most automatics use the planetary gears to provide various reductions ratios. Bands and clutches are used to hold various portions of the gearsets to the transmission case or to the shaft on which they are mounted. Shifting is accomplished, then, by changing the portion of each planetary gearset which is held to the transmission case or to the shaft.

### SERVOS AND ACCUMULATORS

The servos are hydraulic pistons and cylinders. They resemble the hydraulic actuators used on many other machines, such as bulldozers. Hydraulic fluid enters the cylinder, under pressure, and forces the piston to move to engage the band or clutches.

Servos, operated by pressure, are used to apply or release the bands, to either hold the ring gear or allow it to rotate

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The accumulators are used to cushion the engagement of the servos. The transmission fluid must pass through the accumulator on the way to the servo. The accumulator housing contains a thin piston which is sprung away from the discharge passage of the accumulator. When fluid passes through the accumulator on the way to the servo, it must move the piston against spring pressure, and this action smoothes out the action of the servo.

### HYDRAULIC CONTROL SYSTEM

The hydraulic pressure used to operate the servos comes from the main transmission oil pump. This fluid is channeled to the various servos through the shift valves. There is generally a manual shift valve which is operated by the transmission selector lever and an automatic shift valve for each automatic upshift the transmission provides.

Many new transmissions are electronically controlled. On these models, electrical solenoids are used to better control the hydraulic fluid. Usually, the solenoids are regulated by an electronic control module.

There are two pressures which affect the operation of these valves. One is the governor pressure which is effected by vehicle speed. The other is the modulator pressure which is effected by intake manifold vacuum or throttle position. Governor pressure rises with an increase in vehicle speed, and modulator pressure rises as the throttle is opened wider. By responding to these two pressures, the shift valves cause the upshift points to be delayed with increased throttle opening to make the best use of the engine's power output.

Most transmissions also make use of an auxiliary circuit for downshifting. This circuit may be actuated by the throttle linkage the vacuum line which actuates the modulator, by a cable or by a solenoid. It applies pressure to a special downshift surface on the shift valve or valves.

The transmission modulator also governs the line pressure, used to actuate the servos. In this way, the clutches and bands will be actuated with a force matching the torque output of the engine.

## Fluid Pan

### REMOVAL & INSTALLATION

Refer to Section 1 for transmission pan removal and filter service.

## Manual Lever Position (MLP) Sensor/Transmission Range (TR) Sensor

### REMOVAL & INSTALLATION

Unfasten the nut for the manual control lever and ...

... remove the lever from the sensor

Detach the connector from the TR sensor

Unfasten the retaining bolts and ...

... remove the sensor from the transmission

1. Disconnect the negative battery cable.
2. Raise and support the vehicle safely on jackstands.
3. Place the transmission in Neutral.
4. Remove and discard the manual control lever nut, then remove the lever from the transmission.
5. Detach the TR sensor electrical harness connector, remove the TR sensor retaining bolts, then pull the TR sensor off of the transmission case.

To install:

6. Position the TR sensor against the transmission case and loosely install the 2 retaining screws.
7. Attach the TR sensor electrical harness connector.
8. Use an alignment tool, such as the TR Sensor Alignment Tool T93P-70010-A, to align the TR sensor slots.
9. Tighten the TR sensor bolts to 80-100 inch lbs. (9-11 Nm).
10. Position the manual control lever onto the TR sensor, then install the new lever nut to 22-26 ft. lbs. (30-35 Nm).
11. Lower the vehicle.
12. Connect the negative battery cable.

### ADJUSTMENT

Adjusting the MLP sensor

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Park is the last detent when the manual control lever is full forward. Return 2 detents toward the output shaft for Neutral.

1. Position the manual control lever in Neutral.
2. Raise the and safely support the vehicle.
3. Loosen the sensor retaining bolts.
4. Insert Gear Position Sensor Adjuster tool T93P-700 10-A or equivalent, into the slots.
5. Align all 3 slots on the MLP sensor with 3 tabs on the tool.
6. Tighten the attaching screws to 80-100 inch lbs. (9-11 Nm).
7. Lower the vehicle.

## Extension Housing Seal

### REMOVAL & INSTALLATION

#### 2WD Models

The extension housing seal is located at the rear of the transmission case.

1. Raise and support the vehicle safely.
2. Drain the transmission of lubricant.
3. Matchmark the driveshaft to the yoke for reassembly and remove the driveshaft.
4. Remove the old seal using a seal puller or appropriate prytool.

To install:

5. Install a new seal, coated with sealing compound, using an appropriate seal installation tool.
6. Install the driveshaft, making certain to align the matchmark.
7. Lower the vehicle.
8. Fill the transmission with the proper fluid.

#### 4WD Models

The extension housing seal on 4WD drive vehicles is located at the rear of the transfer case. Refer to the Rear Output Shaft Seal procedure in the Transfer Case portion of this section.

## Automatic Transmission Assembly

### REMOVAL & INSTALLATION

#### 4R70W

On 4.6L engine equipped models, remove the rubber access plug to ...

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... access and remove the converter-to-flywheel attaching nuts

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Disconnect the shift linkage

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Disconnect each fluid cooler line from the fittings on the transmission

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Detach the harness connectors from the transmission

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Detach the solenoid body connector

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Remove the fuel line bracket retaining bolt

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Remove the bolt that secures the transmission fluid filler tube to the cylinder and remove the dipstick from the transmission

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1. Place the shift lever in the NEUTRAL position.
2. Disconnect the negative battery cable.
3. Raise the vehicle on hoist or stands.
4. If transmission disassembly is required, drain the fluid.
5. On 4 X 4 vehicles, remove the transfer case. Refer to the procedure in this section.
6. Matchmark and disconnect the driveshaft from the rear axle and slide shaft rearward from the transmission. Install a seal installation tool in the extension housing to prevent fluid leakage.
7. Disconnect the cable from the terminal on the starter motor. Remove the three attaching bolts and remove the starter motor.
8. On 4.2L engine equipped models only, remove the transmission inspection cover.
9. On 4.6L engine equipped models only, remove the rubber access plug.
10. Remove the converter-to-flywheel attaching nuts. Place a wrench on the crankshaft pulley attaching bolt to turn the converter to gain access to the nuts.
11. Disconnect the shift linkage.
12. Disconnect each fluid cooler line from the fittings on the transmission.
13. Place a drain pan under the converter to catch the fluid. With the wrench on the crankshaft pulley attaching bolt, turn the converter to gain access to the converter drain plug and remove the plug. After the fluid has been drained, reinstall the plug.
14. Detach the harness connectors at both the Output Shaft Speed (OSS) sensor, the Transmission Range (TR) sensor and the Vehicle Speed Sensor (VSS).
15. Detach the solenoid body connector.
16. Position a transmission jack under the transmission and raise it slightly.
17. Remove the transmission crossmember.
18. Remove the exhaust Y-pipe.
19. Remove the fuel line bracket retaining bolt.
20. Remove the bolt that secure the transmission fluid filler tube to the cylinder head. Lift the filler tube and the dipstick from the transmission.
21. Secure the transmission to the jack with the chain.
22. Remove the converter housing-to-cylinder block attaching bolts.
23. Carefully move the transmission and converter assembly away from the engine and, at the same time, lower the jack to clear the underside of the vehicle.

To install:

24. Position the converter on the transmission, making sure the converter drive flats are fully engaged in the pump gear by rotating the converter.
25. With the converter properly installed, place the transmission on the jack. Secure the transmission to the jack with a chain.

Align the orange balancing marks on the converter stud and flywheel bolt hole if balancing marks are present.

26. Rotate the converter until the studs and drain plug are in alignment with the holes in the flywheel.

Before torque converter is bolted to the flywheel, a check should be made to ensure that the torque converter is properly seated. The torque converter should move freely with respect to the flywheel. Grasp the torque converter stud. Movement back and forth should result in a metallic clank noise if the converter is properly seated. If the torque converter will not move, the transmission must be removed and the torque converter re-position so that the impeller hub is properly engage in the pump gear.

27. Move the converter and transmission assembly forward into position, using care not to damage the flywheel and the converter pilot. The converter must rest squarely against the flywheel. This indicates that the converter pilot is not binding in the engine crankshaft.
28. Install and tighten the converter housing-to-engine attaching bolts to 30-41 ft. lbs. (40-55 Nm).
29. Install the fuel line bracket and tighten the retaining bolt.
30. Install the exhaust Y-pipe.
31. Install the transmission crossmember.
32. Remove the jack from under the transmission.
33. Install a new O-ring on the lower end of the transmission filler tube. Insert the tube in the transmission case and secure the tube to RH cylinder head with the retaining bolt.
34. Attach the solenoid body connector.
35. Attach the connectors for the OSS, TR sensor and the VSS.
36. Connect the oil cooler lines to the right side of transmission case.
37. Connect the transmission shift linkage.
38. Tighten the torque converter nuts and tighten the nuts to 20-34 ft. lbs. (27-46 Nm).
39. On the 4.6L engine, install the rubber access plug.
40. On the 4.2L engine, install the transmission inspection cover.
41. Install the starter motor.
42. Position the drive shaft yoke inside the extension housing.
43. Install the driveshaft.
44. On 4 X 4 models, install the transfer case. Refer to the procedure as outlined in this section.
45. Lower the vehicle.
46. Connect the negative battery cable.
47. Fill the transmission with approved transmission fluid. Road test the vehicle.

#### E4OD/4R100

Disconnect the oil cooler lines from the fittings on the transmission

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Detach the manual lever position sensor connector

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Detach the solenoid body connector

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Detach the turbine shaft and output shaft speed sensors

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Remove the flywheel inspection cover retaining bolts—gasoline engines

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Remove the flywheel inspection cover retaining bolts—diesel engines

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Remove the flywheel retaining nuts

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Lower the transmission from the vehicle using a suitable jack

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Install Torque Converter Handles T81P-7902-C, or equivalent, at the 12 o'clock and 6 o'clock positions

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1. Disconnect the negative battery cable.
2. Raise and support the truck on jackstands.
3. Place the drain pan under the transmission fluid pan. Starting at the rear of the pan and working toward the front, loosen the attaching bolts and allow the fluid to drain. Finally, remove all of the pan attaching bolts except two at the front, to allow the fluid to further drain. With fluid drained, install two bolts on the rear side of the pan to temporarily hold it in place.
4. Remove the dipstick from the transmission.
5. On 4WD drive models, matchmark and remove the front driveshaft.
6. Matchmark and remove the rear driveshaft. Install a seal installation tool in the extension housing to prevent fluid leakage.
7. Disconnect the linkage from the transmission.
8. On 4WD drive models, disconnect the transfer case linkage.
9. Remove the heat shield and remove the manual lever position sensor connector by squeezing the tabs and pulling on the connector. NEVER ATTEMPT TO PRY THE CONNECTOR APART!
10. Remove the solenoid body heat shield.
11. Remove the solenoid body connector by pushing on the center tab and pulling on the wiring harness. NEVER ATTEMPT TO PRY APART THE CONNECTOR!
12. On 4WD drive models, remove the 4x 4 switch connector from the transfer case. Be careful not to over-extend the tabs.
13. Pry the harness connector from the extension housing wire bracket.
14. On 4WD drive models, remove the wiring harness locators from the left side of the connector.
15. On 4WD drive models, remove the transfer case.
16. Detach the turbine shaft and output shaft speed sensors.
17. Remove the converter cover bolts.
18. Remove the rear engine cover plate bolts.
19. Disconnect the cable from the terminal on the starter motor. Remove the three attaching bolts and remove the starter motor. Disconnect the neutral start switch wires at the plug connector.
20. Remove the converter-to-flywheel attaching nuts. Place a wrench on the crankshaft pulley attaching bolt to turn the converter to gain access to the nuts.
21. Secure the transmission to a transmission jack. Use a safety chain.
22. Remove the rear mount-to-crossmember attaching nuts and the two crossmember-to-frame attaching bolts.
23. Disconnect each oil line from the fittings on the transmission. Cap the lines.
24. Remove the 6 converter housing-to-cylinder block attaching bolts.
25. Carefully move the transmission and converter assembly away from the engine and, at the same time, lower the jack to clear the underside of the vehicle.
26. Remove the transmission filler tube.
27. On F-Super Duty, remove the transmission-mounted brake. See Section 9.
28. Install Torque Converter Handles T81P-7902-C, or equivalent, at the 12 o'clock and 6 o'clock positions.

To install:

29. Install the converter with the handles at the 12 o'clock and 6 o'clock positions. Push and rotate the converter until it bottoms out. Check the seating of the converter by placing a straightedge across the converter and bell housing. There must be a gap between the converter and straightedge. Remove the handles.
30. On F-Super Duty, install the transmission-mounted brake. See Section 9.
31. Install the transmission filler tube.
32. Rotate the converter to align the studs with the flywheel mounting holes.
33. Carefully raise the transmission into position at the engine. The converter must rest squarely against the flywheel.
34. Install the 6 converter housing-to-cylinder block attaching bolts. Snug them alternately and evenly, then, tighten them alternately and evenly to 40-50 ft. lbs. (54-68 Nm).
35. Install the converter drain plug cover.
36. Connect each oil line at the fittings on the transmission.
37. Install the rear mount-to-crossmember attaching nuts and the two crossmember-to-frame attaching bolts. Tighten the nuts and bolts to 50 ft. lbs. (68 Nm).
38. Remove the transmission jack.
39. Install the converter-to-flywheel attaching nuts. Place a wrench on the crankshaft pulley attaching bolt to turn the converter to gain access to the nuts. Tighten the nuts to 20-30 ft. lbs. (27-41 Nm).
40. Install the starter motor. Connect the cable at the terminal on the starter motor. Connect the neutral start switch wires at the plug connector.
41. Install the rear engine cover plate bolts.
42. Install the converter cover bolts.
43. On 4WD drive models, install the transfer case.
44. Connect the speedometer cable.
45. On 4WD drive models, install the wiring harness locators at the left side of the connector.
46. Connect the harness connector at the extension housing wire bracket.
47. On 4WD drive models, install the 4x 4 switch connector at the transfer case.
48. Install the solenoid body connector. An audible click indicates connection.
49. Install the solenoid body heat shield.
50. Install the manual lever position sensor connector and the heat shield.
51. On 4WD drive models, connect the transfer case linkage.
52. Connect the linkage at the transmission.
53. Install the rear driveshaft.
54. On 4WD drive models, install the front driveshaft.
55. Install the dipstick.
56. Install the drain pan using a new gasket and sealer.
57. Lower the truck.
58. Refill the transmission and check for leaks.
59. Connect the negative battery cable.

### ADJUSTMENTS

The automatic transmissions are electronically controlled, no adjustments are possible.