gearbox noise

hi all
i have a problem where when i let off the accelerator in 5th above 65mph i am getting a deep rumbling noise and a bit of vibration coming from around the gearbox or transfer box but its only in 5th and above 65mph? any help would be grateful
my discovery is a 300tdi 1996 with new propshafts that have only done about 300 miles
cheers brett

id check front diff for play in flange first and try with front prop off in diff lock before looking at t/box then g/box

hi mate
i haven't had much experience with these so bare with me
where am i looking for play in the diff?
cheers

diff flange prop bolts too ,removing prop though should eliminate diff or not

so remove the front prop totally then drive it and see if i am still getting the noise?

yes in diff lock

ok i'll try that tomorrow night
if the noise has gone where do you think the problem could be?
cheers

pinion bearings front diff if noise is gone ,most likely

that doesn't sound fun lol
thanks for your help

better than rear gear box bearings