my car is vectra 2.0 16v 1997
i have a problem with the gearbox (automatic), when the car is cold (only after parking for more than 10 hours) when i try to move the gearstick from the P to D or R i feel a shock with a boom sound in the gear beside it is dosen't move smothly it is hard to move the grae stick ,

dose anyone know why?????