That does sound the same as when the diff bearings were disintergrating on my 1.4 tbh, didn't make a difference cornering, but at constant speed droned then if you let of the throttle and coasted down in gear it whined like a bitch lol. Took it to the garage and whipped the drain plug out to make sure there was plenty of oil in it and a string of filings about 3" long came out with the plug. 
I've no idea which gearboxes fit, but surely the NAD revs higher and makes power towards top end so would need different ratios?
I've no idea which gearboxes fit, but surely the NAD revs higher and makes power towards top end so would need different ratios?