Also don't forget that in 1st and 2nd the drive goes on and off the laygear cluster where in 3rd its direct drive so any wear in the laygear bearings or thrusts will show up as will the noise from the gear mesh as there is an axial thrust that is massively reduced if not eliminated in 3rd. From memory, I learnt to drive in an 100E Prefect, there is synchro, of sorts, in 2nd and 3rd, nothing at all in 1st and reverse. As others have said old gearboxes whine, just listen to films of the era of the car, swap out the oil for some fresh EP90 (check I am guessing) and enjoy the thing I am sure it will rattle and whine wonderfully for many a day, long may it do so.
