FL2 TD4 2008 135k miles. Full-on whining noise kicks in immediately when shifting into 5th and 6th gears. Increases as you accelerate but only in the top 2 gears. Goes completely when you change to 4th or lower. Noise is so loud not now using high gears!

Any ideas what it is?
And is it expensive to fix!

Its clearly a gearbox problem as its gear dependant.
Repairs to gearboxes are often expensive and you may need to consider replacing with a reconditioned unit.
But until you've got a diagnosis from a specialist you've no idea of the cost or the options open to you. Jules

Thanks for pointing me in the right direction Jules.

Sounds expensive, especially here in Spain, like its going to add another grand to the £2,000 worth of other issues the car needs resolving to pass its next test. Looks like Im going to have sell it for repairs. Thanks LandRover!

Any idea how much use I can get out of it (not using the offensive gears) before it packs in?

Any idea how much use I can get out of it (not using the offensive gears) before it packs in?

Sorry - no idea - Ive not had a FL2 go majorly wrong in the gearbox dept Jules

Get the oil level checked, and consider changing the oil while you’re at it. It could be as simple as low oil level and a top up may sort it, or at least extend the life of the box. If you do get the oil changed check it’s condition - look for metal particles (indicative of a serious issue), burnt oil, etc. Worth trying before more expensive remedies.

Yes, you are right, oil level well below minimum, needed to add 1L to get it to the halfway mark. Drives much smoother all round - I had thought the roughness was new tyres.

The noise is still there in 5th & 6th although a lot better - more of a hoarse sound than a whine, for now.