gearbox shaking badly

[BL33SU]

im having issues with my 1.8t gearbox, originally thought it was my control arms or parts around that area because while driving the front end shakes/vibrates alot.. so jacked the car up on stands and accelerated and from about 40k's and above the gearbox starts shaking!

shifting gears is perfect, no issues at all. mounts also seem fine too..

anyone else heard of this problem before? been told could be my diff..
not sure if its that or maybe clutch/release bearing?