After driving 35 miles my D2 suddenly start to vibrate quite badly. I pulled in and checked all the wheel nuts as I've just had new tyres all round, nothing loose there. I only had 4 miles to get home which is mostly downhill so managed to coast most of the way home, during this coasting there was no vibration even at 60mph. Soon as I put it in gear the heavy vibration started.

Managed to get home ok and put it up on the ramps, everything seemed secure enough although there was a fair bit of backlash in the transfer box.

The gearbox and clutch were replaced a couple months ago so should be ok, I'm wondering if the transfer box would cause this heavy vibration?

You need to check all the propshaft UJs fastenings the condition of the UJs & the rear rubber doughnut - worn ones could cause those symptons - although it would be surprising to suddenly gets lots of wear.