545RFE Automatic Transmission - Service Information: Overview RAM Pickup 3500

DESCRIPTION

The 545RFE automatic transmissions is a sophisticated, multi-range, electronically controlled transmission which combines optimized gear ratios for responsive performance, state of the art efficiency features and low NVH. Other features include driver adaptive shifting and three planetary gear sets to provide wide ratio capability with precise ratio steps for optimum driveability. The three planetary gear sets also make available a unique alternate second gear ratio. The primary 2nd gear ratio fits between 1st and 3rd gears for normal through-gear accelerations. The alternate second gear ratio (2prime) allows smoother 4-2 kickdowns at high speeds to provide 2nd gear passing performance over a wider highway cruising range.

The hydraulic portion of the transmission consists of the transmission fluid, fluid passages, hydraulic valves, and various line pressure control components.

The primary mechanical components of the transmission consist of the following

1. Three multiple disc input clutches
2. Three multiple disc holding clutches
3. Five hydraulic accumulators
4. Three planetary gear sets
5. Dual Stage Hydraulic oil pump
6. Valve body
7. Solenoid pack

The Transmission Control Module (TCM) is the "heart"or "brain" of the electronic control system and relies on information from various direct and indirect inputs (sensors, switches, etc.) to determine driver demand and vehicle operating conditions. Depending on the vehicle configuration, the TCM may be a standalone module or it may be housed along with the Powertrain Control Module (PCM) in a single module. With this information, the TCM can calculate and perform timely and quality shifts through various output or control devices (solenoid pack, transmission control relay, etc.).

Scheme 49

Transmission identification numbers are stamped (1) on the left side of the case just above the oil pan sealing surface. (Scheme 49) Refer to this information when ordering replacement parts. A label is attached to the transmission case above the stamped numbers. The label gives additional information which may also be necessary for identification purposes.

OPERATION

The 45/545RFE offers full electronic control of all automatic up and downshifts, and features real-time adaptive closed-loop shift and pressure control. Electronic shift and torque converter clutch controls help protect the transmission from damage due to high temperatures, which can occur under severe operating conditions. By altering shift schedules, line pressure, and converter clutch control, these controls reduce heat generation and increase transmission cooling.

To help reduce efficiency-robbing parasitic losses, the transmissions includes a dual-stage transmission fluid pump with electronic output pressure control. Under most driving conditions, pump output capacity greatly exceeds that which is needed to keep the clutches applied. The 68RFE pump-pressure control system monitors input torque and adjusts the pump pressure accordingly. The primary stage of the pump works continuously; the second stage is bypassed when demand is low. The control system also monitors input and output speed and, if incipient clutch slip is observed, the pressure control solenoid duty cycle is varied, increasing pressure in proportion to demand.

A high-travel torque converter damper assembly allows earlier torque converter clutch engagement to reduce slippage. Needle-type thrust bearings reduce internal friction. The 45/545RFE is packaged in a one-piece die-cast aluminum case. To reduce NVH, the case has high lateral, vertical and torsional stiffness. Dual filters protect the pump and other components. A cooler return filter is added to the customary main sump filter. Independent lubrication and cooler circuits assure ample pressure for normal transmission operation even if the cooler is obstructed or the fluid cannot flow due to extremely low temperatures.

Note. Vehicles equipped with ERS (Electronic Range Select) do not provide 2nd gear in limp-in, because the shift lever has no "2" or "1" position.

The hydraulic control system design (without electronic assist) provides the transmission with PARK, REVERSE, NEUTRAL, SECOND, and THIRD gears, based solely on driver shift lever selection. This design allows the vehicle to be driven (in limp"mode) in the event of a electronic control system failure, or a situation that the Transmission Control Module (TCM) recognizes as potentially damaging to the transmission.

The TCM also performs certain self-diagnostic functions and provides comprehensive information (sensor data, DTC's, etc.) which is helpful in proper diagnosis and repair. This information can be viewed with the scan tool.

Note. Before attempting any repair on a automatic transmission, check for Diagnostic Trouble Codes with the scan tool.

Transmission malfunctions may be caused by these general conditions

1. Poor engine performance
2. Improper adjustments
3. Hydraulic malfunctions
4. Mechanical malfunctions
5. Electronic malfunctions

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.

The three input clutches are responsible for driving different components of the planetary geartrain.

The planetary geartrain is located behind the 4C retainer/bulkhead, toward the rear of the transmission. The planetary geartrain consists of three primary assemblies

1. Reaction (3, 4, 8).

Scheme 50

1. Reverse (6).
2. Input (3, 4, 5).

The system locks the shifter into the PARK position. The interlock system is engaged whenever the ignition switch is in the LOCK or ACCESSORY position. An additional electrically activated feature will prevent shifting out of the PARK position unless the brake pedal is depressed approximately one-half an inch. A magnetic holding device in line with the park lock cable is energized when the ignition is in the RUN position. When the key is in the RUN position and the brake pedal is depressed, the shifter is unlocked and will move into any position. The interlock system also prevents the ignition switch from being turned to the LOCK or ACCESSORY position, unless the shifter is fully locked into the PARK position.

The oil pump (2) is located at the front of the transmission inside the bell housing and behind the transmission front cover. see scheme 150

Scheme 51

The oil pump consists of two independent pumps. see scheme 151

Scheme 52

The oil pump also contains a number of valves. The converter clutch switch (3) and control valves (2), pressure regulator valve (5), and converter pressure limit valve (6) are all located in the oil pump valve body. see scheme 152

Scheme 53

A filter seal (2), and a bolt on reaction shaft (4) complete the oil pump assembly.

As the torque converter rotates, the converter hub rotates the oil pump drive gear. As the drive gear rotates both driven gears, a vacuum is created when the gear teeth come out of mesh. This suction draws fluid through the pump inlet from the oil pan. As the gear teeth come back into mesh, pressurized fluid is forced into the pump outlet and to the oil pump valves.

At low speeds, both sides of the pump supply fluid to the transmission. As the speed of the torque converter increases, the flow from both sides increases until the flow from the primary side alone is sufficient to meet system demands. At this point, the check valve located between the two pumps closes. The secondary side is shut down and the primary side supplies all the fluid to the transmission.

The Input and Output Speed Sensors are two-wire magnetic pickup devices that generate AC signals as rotation occurs. They are mounted in the left side of the transmission case and are considered primary inputs to the Transmission Control Module (TCM).

The Input Speed Sensor provides information on how fast the input shaft is rotating. As the teeth of the input clutch hub pass by the sensor coil, an AC voltage is generated and sent to the TCM. The TCM interprets this information as input shaft RPM.

The Output Speed Sensor generates an AC signal in a similar fashion, though its coil is excited by rotation of the park gear teeth. The TCM interprets this information as output shaft RPM.

The TCM compares the input and output speed signals to determine the following

1. Transmission gear ratio
2. Speed ratio error detection
3. CVI calculation

The TCM also compares the input speed signal and the engine speed signal to determine the following

1. Torque converter clutch slippage
2. Torque converter element speed ratio

The Input and Output Speed Sensors are two-wire magnetic pickup devices that generate AC signals as rotation occurs. They are mounted in the left side of the transmission case and are considered primary inputs to the Transmission Control Module (TCM).

The Input Speed Sensor provides information on how fast the input shaft is rotating. As the teeth of the input clutch hub pass by the sensor coil, an AC voltage is generated and sent to the TCM. The TCM interprets this information as input shaft RPM.

The Output Speed Sensor generates an AC signal in a similar fashion, though its coil is excited by rotation of the park gear teeth. The TCM interprets this information as output shaft RPM.

The TCM compares the input and output speed signals to determine the following

1. Transmission gear ratio
2. Speed ratio error detection
3. CVI calculation

The TCM also compares the input speed signal and the engine speed signal to determine the following

1. Torque converter clutch slippage
2. Torque converter element speed ratio

The transmission temperature sensor is a thermistor that is integral to the Transmission Range Sensor (TRS).

The transmission temperature sensor is used by the TCM to sense the temperature of the fluid in the sump. Since fluid temperature can affect transmission shift quality and convertor lock up, the TCM requires this information to determine which shift schedule to operate in.

The Transmission Range Sensor (TRS) is part of the solenoid module, which is mounted to the top of the valve body inside the transmission.

The Transmission Range Sensor (TRS) has five switch contact pins that

1. Determine shift lever position
2. Supply ground to the Starter Relay in Park and Neutral only.
3. Supply +12 V to the backup lamps in Reverse only.

The TRS also has an integrated temperature sensor (thermistor) that communicates transmission temperature to the TCM and PCM.

The Transmission Range Sensor (TRS) communicates shift lever position to the TCM as a combination of open and closed switches. Each shift lever position has an assigned combination of switch states (open/closed) that the TCM receives from four sense circuits. The TCM interprets this information and determines the appropriate transmission gear position and shift schedule.

There are many possible combinations of open and closed switches (codes). Seven of these possible codes are related to gear position and five are recognized as "between gear" codes. This results in many codes which should never occur . These are called "invalid" codes. An invalid code will result in a DTC, and the TCM will then determine the shift lever position based on pressure switch data. This allows reasonably normal transmission operation with a TRS failure.

The TCM utilizes a closed-loop system to control transmission line pressure. The system contains a variable force style solenoid, the Pressure Control Solenoid, which is part of the pressure switch assembly. The solenoid is duty cycle controlled by the TCM to vent the unnecessary line pressure supplied by the oil pump back to the pump inlet. The system contains a Line Pressure Sensor, which is a direct input to the TCM. The line pressure sensor monitors the transmission line pressure and completes the feedback loop to the TCM. The TCM uses this information to adjust its control of the pressure control solenoid to achieve the desired line pressure.

The TCM calculates the desired line pressure based upon inputs from the transmission and engine. The TCM calculates the torque input to the transmission and uses that information as the primary input to the calculation. The line pressure is set to a predetermined value during shifts, to ensure consistent shift quality. During all other operation, the desired line pressure value is adjusted based on torque level and other transmission requirements.

The gear shift mechanism provides six shift positions which are

1. Park (P)
2. Reverse (R)
3. Neutral (N)
4. Drive (D)
5. Manual second (2)
6. Manual low (1)

MANUAL LOW (1) range provides first gear only. Maximum engine braking is also provided in this range. MANUAL SECOND (2) range provides first and second gear only.

DRIVE range provides FIRST, SECOND, THIRD, OVERDRIVE FOURTH, and OVERDRIVE FIFTH gear ranges. The shift into OVERDRIVE FOURTH and FIFTH gear ranges occurs only after the transmission has completed the shift into D THIRD gear range. No further movement of the shift mechanism is required to complete the 3-4 or 4-5 shifts.

The FOURTH and FIFTH gear upshifts occur automatically unless the Tow/Haul or OD Off mode is enabled. No upshift to FOURTH or FIFTH gears will occur if any of the following are true

1. The transmission fluid temperature is below 10° C (50° F) or above 121° C (250° F).
2. The shift to THIRD is not yet complete.
3. Vehicle speed is too low for the 3-4 or 4-5 shifts to occur.

Upshifts into FOURTH or FIFTH will be delayed when the transmission fluid temperature is below 4.5° C (40° F) or above 115.5° C (240° F).

Scheme 54

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Scheme 58

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Scheme 60

Scheme 61

1. Using trim stick (special tool #C-4755, Trim Stick) or equivalent, remove the console bezel trim ring (1).
2. Remove the rubber insert (1) from the console bezel.
3. Remove the fasteners (1) at the front of the console bezel.
4. Using trim stick (special tool #C-4755, Trim Stick) or equivalent, remove console bezel (1).
5. Remove the rubber liners from the center storage tray and cup holders in the console PRNDL bezel, and remove the fasteners (1).
6. Disconnect the power outlet harness connector (1) and the shifter harness connector (2).
7. Place the shifter in park.
8. Remove the fasteners (1), and position the shifter assembly (2) so the cable end is accessible.
9. Disconnect the shift cable retainer (2) from the bracket.
10. Disconnect the shifter cable end (1) from the shifter lever.
11. Remove the shifter assembly.

Scheme 62

Scheme 63

Scheme 64

1. Using trim stick (special tool #C-4755, Trim Stick) or equivalent, remove the console bezel trim ring (1).
2. Remove the rubber insert (1) from the console bezel.
3. Remove the fasteners (1) at the front of the console bezel.
4. Using trim stick (special tool #C-4755, Trim Stick) or equivalent, remove the console bezel (1).
5. Remove the rubber liners from the center storage tray and cup holders in the console PRDL bezel, and remove the fasteners (1).
6. Disconnect the power outlet harness connector (1) and the shifter harness connector (2).
7. Twist the lower trim piece (1) on the base of the shifter knob counterclockwise, then push down to disengage the trim piece (1).
8. Remove the shifter knob.
9. Twist the shift position indicator lamp connector (1) 1/4 turn counterclockwise, then disconnect the lamp from the console PRNDL bezel.
10. Release the clips (1) on the console PRNDL bezel, and remove the console PRNDL bezel.

The tow/haul overdrive OFF (control) switch is located in the instrument panel switch pod. The switch is a momentary contact device that signals the PCM to toggle current status of the overdrive function. Refer to POD, Switch , Description .

At key-on, overdrive operation is allowed. Pressing the switch once enables Tow/Haul mode and the Tow/Haul lamp will be illuminated. In Tow/Haul mode, 5th gear is disabled and 3-4 upshifts are delayed. Shifts into 4th gear are still allowed under steady cruise conditions. Closed throttle downshifts (for improved engine braking) may occur during steady braking maneuvers. Pressing the switch a second time enables OD Off mode, where all 4th and 5th gear operation is inhibited. Pressing the switch a third time restores normal operation. Normal operation is always the default at start-up; the switch must be pressed after each key start if Tow/Haul mode is desired.

The torque converter is a hydraulic device that couples the engine crankshaft to the transmission. see scheme 215 The torque converter consists of an outer shell with an internal turbine (1), a stator (2), an overrunning clutch, an impeller (5), and an electronically applied converter clutch (6). The converter clutch provides reduced engine speed and greater fuel economy when engaged. Clutch engagement also provides reduced transmission fluid temperatures. The torque converter hub (3) drives the transmission oil (fluid) pump and contains an o-ring seal (4) to better control oil flow.

The torque converter is a sealed, welded unit that is not repairable and is serviced as an assembly.

Scheme 65

The impeller is an integral part of the converter housing. see scheme 216 The impeller consists of curved blades placed radially along the inside of the housing on the transmission side of the converter. As the converter housing is rotated by the engine, so is the impeller, because they are one and the same and are the driving members of the system.

Scheme 66

The turbine is the output, or driven, member of the converter. see scheme 217 The turbine is mounted within the housing opposite the impeller, but is not attached to the housing. The input shaft is inserted through the center of the impeller and splined into the turbine. The design of the turbine is similar to the impeller, except the blades of the turbine are curved in the opposite direction.

Scheme 67

The stator assembly is mounted on a stationary shaft which is an integral part of the oil pump. see scheme 218 The stator (1) is located between the impeller (2) and the turbine (4) within the torque converter case.

Scheme 68

The stator contains an overrunning clutch (1-4), which allows the stator to rotate only in a clockwise direction. see scheme 219 When the stator is locked against the overrunning clutch, the torque multiplication feature of the torque converter is operational.

Scheme 69

The TCC was installed to improve the efficiency of the torque converter that is lost to the slippage of the fluid coupling. see scheme 220 Although the fluid coupling provides smooth, shock-free power transfer, it is natural for all fluid couplings to slip. If the impeller (3) and turbine (5) were mechanically locked together, a zero slippage condition could be obtained. A hydraulic piston (6) with friction material (7) was added to the turbine assembly (5) to provide this mechanical lock-up.

In order to reduce heat build-up in the transmission and buffer the powertrain against torsional vibrations, the TCM can duty cycle the L/R-CC Solenoid to achieve a smooth application of the torque converter clutch. This function, referred to as Electronically Modulated Converter Clutch (EMCC) can occur at various times depending on the following variables

1. Shift lever position
2. Current gear range
3. Transmission fluid temperature
4. Engine coolant temperature
5. Input speed
6. Throttle angle
7. Engine speed

The converter impeller (driving member), which is integral to the converter housing and bolted to the engine drive plate, rotates at engine speed. see scheme 221 The converter turbine (driven member), which reacts from fluid pressure generated by the impeller, rotates and turns the transmission input shaft.

Scheme 70

Note. For a visual aid in determining valve location, operation and design Refer to Schematics and Diagrams .

The Solenoid Switch Valve (SSV) is located in the main valve body and directs the output from the L/R-TCC solenoid to either the L/R clutch or the TCC control valves

The Solenoid Switch Valve directs the output pressure from the LR-TCC solenoid. In 1st gear, the SSV will be in the downshifted position, thus directing fluid to the L/R clutch circuit. In 2nd, 3rd, 4th, and 5th gears, the solenoid switch valve will be in the upshifted position and directs the fluid to the torque converter clutch (TCC) switch valve and TCC regulator valve.

When shifting into 1st gear, a special hydraulic sequence is performed to ensure SSV movement into the downshifted position. The L/R pressure switch is monitored to confirm SSV movement. If the movement is not confirmed (the L/R pressure switch does not close), 2nd gear is substituted for 1st. A DTC will be set after three unsuccessful attempts are made to get into 1st gear in one given key start.