Transmission start-up control

DETAILED DESCRIPTION An object of the present invention is to provide an improvement in off-road vehicle transmissions with powershifting under microprocessor control, the improvement providing an automatic and more uniform gear selection at start-up.
In accordance with the principles of the invention, sensors are provided for sensing when the engine is running, a forward/reverse shift lever has been shifted from neutral, or a clutch pedal has been depressed, and whether the vehicle is moving or stationary.
A microprocessor is responsive to the sensors for selecting a first or a second initial powershift gear speed depending on the positions of two range shift levers, the selection being such that the initial gear speed ratio selected is kept to a minimum consistent with the shift lever positions.
The initial powershift gear selection is made only if the vehicle is not moving, and the electro-hydraulic powershift clutches are engaged only if the microprocessor senses a sequence of conditions comprising the engine running followed by either a shifting of the forward/reverse lever from neutral or a movement of the clutch pedal from a depressed position to a released position.
Another object of the invention is to provide a method and apparatus for selecting the initial powershift gear selected at start-up.
When a first range select lever selects a high range of gears, the lowest powershift gear is automatically selected but if the range select lever selects a low range then the highest powershift gear is selected.
When the first range select lever selects one of two ranges within each of two ranges selectable by a second range select lever, the position of the second lever determines the powershift gear selected at start-up.
Other objects of the invention and its mode of operation will become apparent upon consideration of the following description and the accompanying drawings.