Shift Mechanism

MECHANISM-SHIFT
DESCRIPTION





The automatic transmission is operated with the help of a shift lever assembly (SLA) (1) located in the floor console. There are four positions to which the selection lever can be shifted: P, R, N, D. In addition, the selector lever can be moved sideways (+/-) in position D to adjust the shift range.

All selector lever positions, as well as selected shift ranges in position D, are identified by the SLA. The information is then sent to the transmission control module (TCM) via a hardwire connection. At the same time, the selector lever positions P, R, N and D are transmitted by a shift cable to the selector shaft in the transmission.

The SLA is comprised of the following functions:
^ Key lock: Depending on the selector lever position, the ignition cylinder is locked/unlocked, i.e., the ignition key can be removed only if the selector lever is in position P. A park lock cable is used to perform this function.
^ Park lock: The selector lever is not released from position P until the brake pedal has been applied and the ignition key is in ACC or ON positions. Shift lock is controlled by the brake light switch in conjunction with a locking solenoid in the SLA. As soon as the brake pedal is applied firmly, the locking solenoid is energized and retracted to unlock the selector lever. If the selector lever cannot be moved out of position P due to a malfunction, the shift lock function can be overridden (2).
^ Reverse inhibitor: As soon as the vehicle speed exceeds approximately 4-7 mph, it is no longer possible to move the selector lever from position N to position R. The reverse inhibit functionality is controlled by the same solenoid as the park lock. As the vehicle accelerates past the calibrated speed threshold, the solenoid is energized to block the sideways motion of the shift lever necessary to move from NEUTRAL to REVERSE. The reverse inhibit is not released until the vehicle speed falls below approximately 4-7 mph and the shifter is moved out of the D shifter position.

OPERATION
With the selector lever in position D, the transmission control module (TCM) automatically shifts the gears that are best-suited to the current operating situation. This means that shifting of gears is continuously adjusted to current driving and operating conditions in line with the selected shift range and the accelerator pedal position. Starting off is always performed in 1st gear.





The selector lever positions are determined by a sensor assembly internal to the shift lever assembly (SLA). The sensor assembly identifies the various positions of the SLA according to the following table.

The current selector lever position or, if the shift range has been limited, the current shift range is indicated in the instrument cluster display.

The permissible shifter positions and transmission operating ranges are:
^ P = Parking lock and engine starting.
^ R = Reverse.
^ N = Neutral and engine starting (no power is transmitted to the axles).
^ D = The shift range includes all forward gears.

The shift range can be adjusted to the current operating conditions by tipping the selector lever to the left-hand side (-) or the right-hand side (+) when in position ID. If the shift range is limited, the display in the instrument cluster indicates the selected shift range and not the currently engaged gear.
^ 4= Shift range is limited to gears 1 to 4.
^ 3= Shift range is limited to gears 1 to 3.
^ 2= Shift range is limited to gears 1 to 2.
^ 1= Shift range is limited to the 1st gear.
Tipping the shift lever will have the following results:
^ Tipping the selector lever toward % one time after another: The shift range is reduced in descending sequence by one gear each time, i.e., from D - 4 - 3 - 2 - 1. If the selected limitation of the shift range would result in a downshift causing excessive engine speed, the shifting is not executed and the engaged gear as well as the shift range remain unchanged. This is to prevent the engine from overspeeding. Engine retardation is low with the selector lever in position ID. To make use of the full braking power of the engine, manual downshifting by tipping the lever towards the left-hand side is recommended. If this has been done, subsequent upshifting must be carried out manually as well.
^ Tipping the selector lever toward % and holding it in this position: The currently engaged gear in range ID is indicated in the instrument cluster display and the shift range is limited to this gear.
^ Tipping the selector lever toward + one time after another: The shift range is increased by one gear each time and the increased shift range is displayed in the instrument cluster; possibly, the transmission upshifts to a faster gear.
^ Tipping the selector lever toward + several times: The shift range is increased by one gear each time the lever is tipped until the shift range ends up in ID.
^ Tipping the selector lever toward + and holding it in this position: The shift range is extended immediately to ID, shift ranges are indicated in ascending sequence; possibly, the transmission upshifts to a faster gear due to the extension of the shift range.