Outer Limits 4x4 Board

Hi.
Im brand new here and i have got my self a 94 disco. i got it aprox. 3 months ago and have just found this forum. so its a 2.5 TDi manual discovery its got 235000 on it and i've taken in off road a couple of times now.
here is the problem.

When i was comming home from work today, i was taking off from a set of lights and i started to hear this horrable noise. it sound's like its comming from the gear box and it only happens when the clutch is out. It doesn't happen when its rolling down a hill or when the engine is reved with the clutch in.
i checked all the oil in it about 2.5 weeks ago before my last 4wd trip and they were all up to the required level.
does anyone have any suggestions.

could be anything in drivetrain raelly. Does it happen ALL the time when in gear? Is it worse during certain activiteis ie, engine brakeing, hard accell etc? What sort of noise? Loud clunking? A 'wiry' sorta rattleing noise?

I've had 2 such noises in my time One was a worn gear, other was uni's. Neither of which should go in a new car (but hey, its a rover - jk) . Have you been throught deep water/mud recently?

it happens most of the time when in gear but is worse when accell its a kinda whir noise couldnt hear any clunking.
i went through some small puddles about w/end before last.
forgive my stupidity but what does water/mud have to do with the noise. the only thing i can think is if mud is stuck somewhere but i don't think that'd cause the noise.

throwout bearing or whatever its called

Just sounds like the normal transfer case whir to me, does it increase when you accelerate and then decrease when you decelerate ? If it stops when you push the clutch in then you may be due for a new clutch, at those k's if it hasnt been replaced already i would do it soon - release bearing could be on its way out, nothing major just noisy.

didnt notice it was 94 mod, for sum reason thought u said it was new .... water/mud matters if u get water in ur tranny/gear box, makes one hellofa noise when a gear goes .... it could be what others have suggested, or your Uni (universal joints) on your driveshaft. Get under there, leave it outta gear and shake it around. There shouldn't be any play in it/rattle. (correct us if i'm wrong anyone, not a huge exp with em ), but from memory thats what mech told us to do last time.

sounds like a noisy thrust bearing to me

Insane - I thought a thrust bearing noise would be more noticeable when the car is not moving and in neutral and sound would change when you press clutch in?