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Home >> Jeep >> 2021 >> Compass Altitude, FWD >> Repair and Diagnosis (Single Page) >> Transmission >> Transmission Control Systems >> F21-250 Gen III Automatic Transmission (Service Information) >> Description And Operation >> Operation >> Notes

Description And Operation: Operation: Notes

The 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.

The hydraulic control system design (without electronic assist) provides the transmission with REVERSE, FIFTH and THIRD. 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.

Lock up control / Slip control  - Based on output rpm signals [SP], signals from the engine control unit (engine rpms and throttle opening) and vehicle speed, smooth lock up control is performed. Also, the slip rate is detected by adding input rpm signals [NIN], and slip control is performed. Since the TCM performs shift control learning and garage shift control learning, it provides smooth clutch engagement at gear shifting and smooth and delicate shifting while driving.

Manual shift control  - By moving the shift lever from the "D" position into the manual shift position and shifting into + (upshift) or - (downshift), the driver can select the desired gear, enabling sporty driving that feels like a manual transmission

Self learning control  - Since the TCM performs shift control learning and garage shift control learning, it provides smooth clutch engagement at gear shifting and smooth and delicate shifting while driving.

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. Additionally, the ability to calibrate the TCM with the scan tool allows for the transmission to deliver optimum shift quality to customers with diverse vehicle applications.

FUNCTIONS OF CLUTCHES AND BRAKES

COMPONENT FUNCTION
C1 CLUTCH Connects the front planetary carrier to the rear planetary rear sun gear
C2 CLUTCH Connects the intermediate shaft to the rear planetary carrier.
C3 CLUTCH Connects the front planetary carrier to the rear planetary middle sun gear.
B1 BRAKE Locks the rear planetary middle sun gear.
B2 BRAKE Locks the rear planetary carrier.
F1 ONE WAY CLUTCH Locks the counterclockwise rotation of the rear planetary carrier.