At least one of the Scanias on the X84/X85 has (for some considerable time) a 'noisy' transmission, (a groaning whine above 25mph).
I would suggest 'final drive' (rear axle) though it might be the actual gearbox (difficult to differentiate without 'tests' - or experienced opinion).
Some on here have predicted the end of the B9TLs on the TEN, but IMO they are just fine (apart from the occasional cooling system overflow).
RE: Go North East: Latest News & Discussion - February 2017