help! i have a m reg 300tdi which makes a noise when 30mph is reached,suspect something amiss in the transmission,but it still makes the noise in neutral or when the clutch is dipped,the wheel bearings seem ok any ideas anyone please?

hi all having burst through male menopause and/or mid-life crisis i find myself the novice owner of 2 discovery's, i don't know anything about mechanicals but have a lot of fun with them