UK Car Repair: Vibrating when changing gears, shaft bearings, output shaft

Question
I have got a 2003 Vauxhall Zaphfria Diesel.

It vibrates when in gears 1,2, and sometimes 3.

Took it to my local garage but they couldnt pin point the problem.

Have you any ideas.

Thanks
Melanie

Answer
Bad input/output shaft bearings on one side of the box or... rough engine power (one cylinder under-powered), or worn CV joint causing "axle tramp".
Proper diagnosis would be to listen to the gearbox in action on a rolling road in case of suspected gearbox wear or to run engine diagnostics to see if there is some fault with the engine.
could be low compression on one or more cylinders or as said, some bearing on one side of the gearbox.