Shift Patterns

Shift Patterns
When the battery has been disconnected and reconnected, some abnormal drive symptoms can occur while the vehicle relearns its adaptive strategy. The customer needs to be notified that they can experience slightly different upshifts (either soft or firm) and that this is a temporary condition and will eventually return to normal operating condition.

The transmission upshifts and downshifts are firmer with tow/haul on than when tow/haul is off.

Upshifts
Transmission upshifting is controlled by the Powertrain Control Module (PCM). The PCM receives inputs from various engine or vehicle sensors and driver demands to control shift scheduling, shift feel and Torque Converter Clutch (TCC) operation.

Downshifts
Under certain conditions the transmission will downshift automatically to a lower gear range (without moving the transmission range selector lever). There are four categories of automatic downshifts; Coastdown, Torque Demand, Forced or Kickdown shifts and grade braking.

Coastdown
The coastdown downshift occurs when the vehicle is coasting down to a stop.

Torque Demand
The torque demand downshift occurs (automatically) during part throttle acceleration when the demand for torque is greater than the engine can provide at that gear ratio.

Kickdown
For maximum acceleration, the driver can force a downshift by pressing the accelerator pedal to the floor. A forced downshift into a lower gear is possible below calibrated speeds. Specifications for downshift speeds are subject to variations due to tire size, engine and transmission calibration requirements.

Grade Braking
During tow/haul operation, depending on conditions, automatically scheduled downshifts may occur to increase the level of engine braking, particularly on down grades.