A broad ratio spread from First to the Fifth was selected to minimize fuel consumption and reduce powertrain noise during cruising. An aggressive First-gear ratio provides excellent launch performance, and evenly spaced gear ratios provide smooth acceleration through the gears.
World-class efficiency is achieved through physical and electronic means. This transmission uses bearings to reduce friction in many locations where other transmissions may utilize bushings. The transmission also uses a unique scavenging system that removes oil spun off of the rotating parts by centrifugal force through strategically placed slots in the outside of the case. This saves energy that would be consumed by internal parts rotating in oil. Lubricating holes in the clutches are also positioned to promote quick passage of the transmission fluid through the discs, minimizing viscous losses due to trapped oil.
The shift schedule adapts to individual driving style, driving situation and road conditions, altering shift points based on an accelerator pedal usage, brake usage, lateral acceleration, altitude and load on the car as a result of grades. Electronically controlled engine torque management provides quick wide-open-throttle up shifts and quick two-step (4-2 or 3-1) kick-down shifts that are exceptionally smooth.
Fully adaptive electronic control of all shifting makes shifts very smooth. The system monitors the transmission as shifts occur and adjusts hydraulic pressure as needed. In so doing, the controls make the powertrain feel responsive without harshness.
Driver recognition software alters shift points based on accelerator pedal usage, brake usage and lateral acceleration. This does not require a compromise between sporty and economical operation, nor is it a question of choosing one or the other.
A torque management system uses engine torque modeling to facilitate smooth transmission shifting. Because of electronic throttle control, torque management is more sophisticated and covers a broad torque range.
Torque converter clutch slippage is electronically modulated and provides for partial engagement in Third, Fourth or Fifth gears. This results in improved shift feel, fuel economy, driveability and cooling. It can be used at lower speeds to provide benefits over a broad speed range. The system disengages as required to provide optimal performance.
The 545RFE five-speed transmission has been refined to offer smoother operation and better economy while improving the performance and towing capability of the vehicle. To accomplish all this, several features were added, including a redesigned solenoid to provide quieter operation when shifting from "park" into "drive." A turbine damper also improves NVH, related to torque converter application.
The 545RFE continues to offer dual second-gear ratios to provide a balance of performance and fuel economy. Depending on driving conditions, the transmission will select the more appropriate second gear. A secondary overdrive ratio increases highway fuel economy and reduces engine noise at high speeds.
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:
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.).
The 65RFE transmission 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 improve efficiency, the transmission 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 65RFE 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 65RFE is packaged in a one-piece die-cast aluminum case. To reduce NVH, the case has high lateral, vertical and torsional stiffness. It is also designed to maximize the benefit of the structural dust cover that connects the bottom of the bell housing to the engine bedplate, enhancing overall power train 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: Note that 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-in" 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 appropriate scan tool.
NOTE: After selecting any gear range, wait a moment to allow the selected gear to engage before accelerating. This is especially important when the engine is cold. If there is a need to restart the engine be sure to cycle the key to the LOCK position before restarting. Transmission gear engagement may be delayed after restarting the engine if the key is not cycled to the LOCK position first.
NOTE: Towing the vehicle, coasting, or driving for any other reason with selector lever in N (Neutral) can result in severe transmission damage. Refer to "Recreational Towing" in Section 5 and "Towing a Disabled Vehicle" in Section 6 of your owner's manual.
The Electronic Range Select (ERS) shift control allows you to move the shifter left (-) or right (+) when the shifter is in the D (Drive) position, allowing the selection of the desired top gear. For example, if the driver shifts the transmission into 3 (third gear), the transmission will never shift above third gear, but can shift down to 2 (second) or 1 (first), when needed.
NOTE: To select the proper gear position for maximum deceleration (engine braking), move the shift lever to the left "D(-)" and hold it there. The transmission will shift to the range from which the vehicle can best be slowed down.
The overdrive automatic transmission contains an electronically controlled fourth and fifth speed (Overdrive). On prior generation models, the Overdrive "On/Off" button was mounted to the front side of the shifter. For 2005-up models, the button is on the center instrument panel switch array and is labeled as "Tow/Haul". The transmission will automatically shift from 3rd gear to Overdrive if the following conditions are present:
NOTE: If the vehicle is started in extremely cold temperatures, the transmission may not shift into Overdrive and will automatically select the most desirable gear for operation at this temperature. Normal operation will resume when the transmission fluid temperature has risen to a suitable level.
If the transmission temperature gets extremely hot, the transmission will automatically select the most desirable gear for operation at this temperature. If the transmission temperature becomes hot enough, the "TRANSMISSION OVERTEMP" message may display and the transmission may downshift out of Overdrive until the transmission cools down. After cooldown, the transmission will resume normal operation.
In high ambient temperatures with sustained high engine speed and load, an upshift followed shortly thereafter by a downshift may occur. This is a normal part of the overheat protection strategy when operating in the "Tow / Haul" mode. The transmission will downshift from Overdrive to the most desireable gear if the accelerator pedal is fully depressed at vehicle speeds above approximately 35 mph (56 km/h).
When driving in hilly areas, towing a trailer, carrying a heavy load, etc., and frequent transmission shifting occurs, press the "Tow / Haul" button. This will improve performance and reduce the potential for transmission overheating or failure due to excessive shifting. When operating in "Tow / Haul" mode, the transmission will shift to 3rd gear and 4th will be enabled under steady cruise conditions.
The "Tow / Haul" light will illuminate in the instrument cluster to indicate when the switch has been activated. Pressing the switch a second time restores normal operation. If the "Tow / Haul" mode is desired, the switch must be pressed each time the engine is started.
A feature designed to improve fuel economy is included in all automatic transmissions. A clutch within the torque converter engages automatically at a calibrated speed at light throttle. It engages at higher speeds under heavier acceleration. This may result in a slightly different feeling or response during normal operation in high gear. When the vehicle speed drops below a calibrated speed, or during acceleration, the clutch automatically and smoothly disengages. The feature is operational in Overdrive and in Drive.
NOTE: The torque converter clutch will not engage until the transmission fluid and engine coolant are warm [usually after 1-3 miles (1.6 - 4.8 km) of driving]. Because the engine speed is higher when the torque converter clutch is not engaged, it may seem as if the transmission is not shifting into Overdrive when cold. This is normal. Pressing the "Tow / Haul" button, when the transmission is sufficiently warm, will demonstrate that the transmission is able to shift into and out of Overdrive.
NOTE: If the vehicle has not been driven in several days, the first few seconds of operation after shifting the transmission into gear may seem sluggish. This is due to the fluid partially draining from the torque converter into the transmission. This condition is normal and will not cause damage to the transmission. The torque converter will refill within five seconds of shifting from Park into any other gear position.
If the vehicle becomes stuck in snow, sand, or mud, it can often be moved by a rocking motion. Move the gear selector rhythmically between D (Drive) and R (Reverse), while applying slight pressure to the accelerator.
NOTE: The Electronic Stability Program (ESP) and Traction Control (if equipped) should be turned OFF before attempting to rock the vehicle. The least amount of accelerator pedal pressure to maintain the rocking motion without spinning the wheels or racing the engine is most effective. Racing the engine or spinning the wheels, due to the frustration of not freeing the vehicle, may lead to transmission overheating and failure. Allow the engine to idle with the transmission selector in N (Neutral) for at least one minute after every five rocking-motion cycles. This will minimize overheating and reduce the risk of transmission failure during prolonged efforts to free a stuck vehicle.
CAUTION! When "rocking" a stuck vehicle by moving between "First" and R (Reverse), do not spin the wheels faster than 15 mph (24 km/h), or drivetrain damage may result.
Autostick is a driver-interactive transmission that offers manual gear shifting capability to provide the driver with more control. Autostick allows the driver to increase engine braking ability, control upshift and downshift points, and enhance the driving experience. This system can also provide the driver with more control during passing, city driving, mountain driving, trailer towing, and many other situations.
By placing the shift lever in the D (Drive) position the lever can be moved from side to side. This allows the driver to engage the AutoStick mode. Moving the shift lever to the right (+) or the left (-) will engage the Autostick mode. In normal driving mode (Boxed "D" displayed in the PRNDL), moving the shift lever to the right (+) will engage the Autostick mode putting the transmission in the currently engaged gear. Moving the shift lever to the Left (-) will engage the Autostick mode and downshift the transmission 1 gear. For example, the transmission is in Normal Mode and is currently operating in 3rd gear, a boxed D is displayed in the PRNDL, a push to the right will engage the Autostick mode in 3rd and a Boxed 3 will be displayed in the PRNDL. A push to the left (-) will engage Autostick mode and downshift to 2nd gear and a Boxed 2 will be displayed in the PRNDL. Once Autostick mode is engaged a move to the Right (+) or left (-) will trigger a upshift (+) or trigger a downshift (-).
NOTE: In the Autostick mode, the transmission will only shift up and down when Left or Right (D-/D+) is manually selected by the driver.
The transmission will not honor a downshift command if the downshift would result in a engine overspeed condition. The transmission will always honor a upshift command from 1st to 2nd gear, however 2nd - 3rd, 3rd - 4th, and 4th - 5th upshift commands will not be honored if the vehicle speed is to low to maintain operation in the commanded gear. The transmission will automatically downshift as the vehicle slows to a stop.
When in the Autostick mode, as the engine RPM nears the engine maximum speed, an 'UPSHIFT' message will appear in the Electronic Vehicle Information Center (EVIC) portion of your instrument cluster. This message appears in order to alert the driver that the engine speed is approaching it's maximum value and a upshift to the next gear is required. In the event that the driver does notupshift, the engine control system will limit the engine speed to protect the engine.
Shifting into or out of the Autostick mode can be done at any time without taking your foot off the accelerator pedal. When the driver wishes to engage Autostick, simply move the shift lever to the Left or Right (D-/D+) position while in D (Drive).
Hold the shift lever to the right for at least one second to disengage Autostick. The transmission will now operate automatically; shifting between the five available gears.
Autostick General Information
Chrysler Group LLC will initially receive the new 8-speed transmissions from the ZF Getriebe GmbH plant in Saarbrücken, Germany. In parallel with Chrysler Group, ZF is setting up a new transmission production plant in North America, where the 8-speed transmissions will be produced. Chrysler Group is licensed to produce the new 8HP's at the company's Indiana Transmission Plant I and the Kokomo casting plant, starting in 2013.
Compact and lightweight, the new transmission required no structural changes to either vehicle and despite the addition of more gears, the transmission actually weighs just 3kg more than the outgoing five speed automatic transmission. The addition of three more gear ratios in the proven ZF eight-speed automatic transmission design help to reduce the gaps normally associated with upshifting and downshifting. Passengers will experience world-class levels of refinement due to small, evenly spaced ratios that provide quicker acceleration and smoother shifts.
Fully electronic and aided with software that provides an adaptive shifting strategy, the 845RE has been designed to provide optimal shifting characteristics consistent with the Chrysler and Dodge brands. Adaptive shifting takes into account a number of variables including engine torque gradients, kick down, longitudinal and lateral acceleration, hill detection, friction detection and downshift detection in determining shift patterns. Additional parameters include vehicle speed control, electronic stability control activation and high temperatures that can affect transmission shifting.
High efforts in shifting also have been eliminated with gear selection controlled by a shift-by-wire system. The position selected by the driver (P, R, N, D) is transmitted electronically with no mechanical linkage from the shifter to the outside of the transmission. Elimination of this linkage removes any shift effort from the driver's gear selection. Shift-by-wire also allows improved calibration and smoothness of garage and parking lot shifts.
All shifts, whether single, double or multiple are performed as a direct result of the pedal position. Downshifts are made with very short response times and lead directly to the requested gear. Multiple upshifts can be decoupled temporarily if the torque request changes during the upshift. This helps eliminate the shift searching of the transmission.
Quicker shifts are possible as a result of a "Sport" shift mode that requires simple driver input. When the driver chooses to let the transmission shift in "Sport" mode, gear changes are quicker and revs are held higher for even more performance-oriented acceleration and higher shift dynamics. For even more control, the driver can also use a pair of die-cast steering-wheel mounted paddle controls and view gear selection through an all-new full-color EVIC centered in instrument cluster.
Additionally, lower viscosity transmission fluid is used resulting in improved transmission efficiency and fuel economy improvements especially during cold environments or vehicle start-up. The 845RE also is "fill for life" not requiring oil changes during normal driving conditions.
The 8HP45 Transmission Control Module Assembly (TCMA), which is integrated into the valve body, provides fully synchronized clutch-to-clutch shifting through four planetary gear sets. The TCMA includes a mounting plate that holds the Transmission Control Module (TCM) and a molded wiring harness for connection to various transmission sensors and solenoids. The valve body assembly contains all the sensors and solenoids required for operation, completely inside the transmission. Eight speeds allow the engine to maintain its optimal rpm range, increasing fuel economy and performance.
Transmission control is performed by the TCM based on hard-wired and CAN bus signals from sensors and modules. The TCM receives driveability data from the Powertrain Control Module (PCM) and other modules over the CAN-C bus. It also receives shift lever position information from the electronic shifter over a dedicated transmission CAN bus. The TCM processes this input data and controls operation of the torque converter clutch, park lock system, solenoid valves, and pressure regulating valve.
The input and output speed sensors are Hall-effect sensors that measure shaft rotational speed. The input speed sensor is located at the top, near the center, of the of the TCMA and reads input shaft speed from the magnetic ring on the P2 carrier. The output speed sensor is located at the back of the TCMA and reads output shaft speed from the P4 carrier
8HP45 Gear Ratios: