gearbox whine

[tropicalpalmtree]

does anyone know what part of my transmission could be at fault, its 5 speed manual awd and has the following symptoms

-quiet but noticable whine on deceleration in all gears
-occasionally a prominent high pitched whine on deceleration and briefly on acceleration until the revs pick up (kind of like a hearing a plane engine from a distance)
-shifting is okay, but if you try to aggressively shift into 2nd or 4th (like you would on a drag strip) it misses the gear completely (gear bushes changed to solid mounts so these can be ruled out)

car was making what i can only describe as a loud supercharger whine the other day while in motion

a few months ago i was greeted with a brutal grinding noise from the gearbox, this lasted for a few weeks until one day the noise disappeared, at which point these problems began, the power delivery has not been effected at all.

any ideas? thanks

 

[T9 man]

Is it possible that the issue might be down to the Haldex coupling units or similar transfer boxes?
These are prone to failure when you least expect it, plus they are oil dependent which must be of the correct type and of the correct level. I am also lead to believe that the filters play an extremely important part in the units performance.