Land Rover Freelander transmission

The vehicle makes a noise from the automatic transmission when the vehicle changes gear from 1st - 2nd, it sounds almost like pressure building and then releasing through a valve, but the noise is quite loud and disturbing, Landrover replaced the gearbox in May, but the vehicle still makes the same noise. I am aware of another Freelander, same model, that makes the same noise, Lnadrover are at a loss and are calling the problem a ''characteristic''. Any help would be gratefully received.