Patent ID: 7713169

Claim:
A method of controlling a vehicle transmission during a gear change thereof, the vehicle transmission including a power shift gearbox and a range shift gearbox, the power shift gearbox having a power shift input shaft, a power shift output shaft, power shift input gearing and power shift output gearing, and a plurality of power shift clutches to drivingly connect the power shift input gearing and the power shift output gearing, the range shift gearbox having a range shift input shaft drivingly connected to the power shift output shaft, a range shift output shaft and range selection gearing to drivingly connect the range shift input shaft and range shift output shaft, the method comprising the steps of: operating the plurality of power shift clutches to disengage the power shift input gearing and the power shift output gearing, disengaging the driving connection between the range shift input shaft and the range shift output shaft by means of the range selection gearing; engaging at least two of the power shift clutches to vary the rotational speed of the power shift output shaft and hence the range shift input shaft, and operating the range selection gearing to establish a driving connection between the range shift input shaft and the range shift output shaft.