Automatic Functions In Manual Mode
When in manual mode there are certain functions which occur automatically to prevent drivetrain damage and improve driveability:
- Engine Overspeed Prevention: To prevent engine over-rev, the TCM will upshift automatically just prior to maximum engine cutoff.
- Kickdown: If plausible, the TCM will automatically shift down to the next lower when a kickdown request is received.
- Decelerating: If in 5th gear and coasting to a stop, the TCM will automatically down shift to 4th gear at approximately 31 mph and then 3rd gear at approximately 19 mph. The automatic downshift allows for an acceptable gear when re-accelerating. (6 cylinder models will shift to 2nd gear when stopping vehicle).
- Implausible Gear Requests: Certain shift requests are ignored by the TCM. For example, requesting a downshift at a high rate of speed would be ignored. Any shift request that would cause the engine to exceed the maximum RPM limit would not be allowed. Also starting out in a high gear is also not allowed. Only 1st, 2nd or third gear is allowed when accelerating from a stop. See Fig 1 .