I have a 2004 Discovery 11 Td5 which developed this humming/vibrating noise in the last 2 days. When I put the gear in neutral it stays, it sounds like driving a vehicle with new tyres on a cement/concrete freeway. My question: What can be the cause, where can I start looking at. Any help will be highly appreciated, Disco Mike, maybe if you have time? I pulled away the other day with the vehicles handbrake still engaged and only realised it after about 400 meters of driving, now also noticed some oil against the Discos chassis to the back of the handbrake drum. Could this have caused this noise(loss of oil) Thanks for this forum, very informative.

 

Check the fluid level in your transfer case, sounds like you have a leak and the noise maybe because you are low on gear lube.
The fill/check plug is at the 10 o'clock position as you are looking at the parking brake drum.