Oh, there it is, right.
I've had a similar problem and I'm ignoring it!
You've just lifted the car, right. Have a look in the RRC forum, near the top. A guy from Greece is saying that a lot of them start having t-box probs a while after fitting a lift kit.
You're probably aware by now that when you lift the car you get pulsing in the front prop, and transmission rumble. This will be worse if you've fitted castor correction arms already.
Basically the extra strain on the front prop caused by the pulsing is finding the weaknesses in your transmission, so it's found the play and is now liberally shaking the t-box output as you drive. I understand that the output bearing is a plain roller, and I have read that the output shaft is one of the wear points of a B-W T-box, which I have.
You can fit a new oil seal for now and think about getting a TD5 front prop or Cardan jointed one from Scorpion (take Tim's advice thou' and go to their supliers) whilst you contemplate the difficulty of stripping the box to overhaul it. I've put off buying second hand because your'e only delaying the inevitable, unless you find a recon one that's had little use since.