Im having issues with a droning / rumbling noise in the 6 speed Tremec gearbox fitted to my 3 month old BF GTP. The Dealer has fitted 2 new gearboxes as they say this is a known issue that Ford / FPV refer to as " 5th Gear rumble". The noise only happens in 5th or 6th gear at between 100 and 115 km/hr either under load or on overrun.Put it back to 4th and no issue ( except for the revs!). The first box they fitted was a "certified" box from Tremec with new gear cut profiles, but that was worse and sounded like a mini with a straight cut gearbox. Ford and FPV have wiped their hands saying there is nothing more they can do....is anyone else having the same issue and is their a fix?