So eventually I decided it was time to see what was wrong with my gearbox as the noise wasn't getting any better.
First fun was getting it out! Luckily I had also decided to remove large parts of the engine to sort an oil leak from the rear seal of the valley gasket so gearbox and bell housing top attachment bolts could be accessed from the engine bay!
The box has now been disassembled and this is the result:
The summary so far is this:
1) Whining - The reason why you are experiencing excessive noise is because the forward sun gear (which transmits drive in first and second gear) shows evidence of tooth damage. See pictures with white arrows. There is a ‘pitting’ effect on the gears. As a result, the sungear and the gears associated with this part (also known as the planetary gear cluster set) will have to be replaced.
2) Brake bands are worn, one much worse than the other. See picture, these will be replaced with new.
3) Clutch plates again are worn and are near the end of their life. These will be replaced with new, see pictures.
4) Although you wouldn’t have been aware, when I stripped the gearbox down I found two rogue bolts lying in the sump. It appears the gearbox has been overhauled before and these bolts were not tightened and fell out of the valve body. They could have ended up in the gears and this would have caused serious problems!
So it would seem a full overhaul was due!