I think I found the actual, definitive source of my gearbox noise. The input shaft here is locked in place and does not spin against the main shaft when in 4th gear. Here are the bearings where it rotates when in any gear other than 4th...where is the bearing cage??
Here are eleven roller bearings around the drive shaft. The input shaft is in my left hand which sits over these roller bearings.
There is a hard plastic residue sprayed all over the underside of the input shaft. Was this a plastic bearing cage?? Did the transmission massively overheat at some point?
Part 43: "Pilot Bearing"
Part 42: "Input shaft"
The image shows a bearing assembly with cage.
edit: I got a metal cage (h suffix) replacement for ~$12 from Bearing Wholesalers. Ford were charging $95 for the plastic cage TN version. :(
