td5 whining in 5th

hi
can anyone give me a bit of advice please just driven over to england from ireland and whilst driving on the motorways I noticed when I changed up from 4th to 5th that a whining started on acceleration only. As soon as i take my foot off it stops. Has anybody any experience of this? Will it make it back to Ireland? Any advice much appreciated.
steve

My Td5 did this on a holiday to France, and 50 miles from Calais the gearbox gave up. Layshaft bearings had failed and I lost all drive except 4th (direct drive) with which I managed to limp it home to Dover.