Dexta gearbox

[Trevorthetractor]

59 Dexta gearbox rebuild, help and advice please.
Under load the gearbox or back end seems to jump, my thinking it is a bearing failure. So far I have split the back end from the gearbox hoping to find the fault but nothing so far the rear gearbox plate will not come off so there must be something holding it together?
Today’s tasks to split the engine at the clutch hosing and go from there, reading the manual special tools are suggested but can the box be fixed without? Otherwise I need to find someone to do the repair in the UK.
Any help or advise please.

[Old Hywel]

Sure it’s the gearbox? Always the same gear? Possibly teeth off the differential.

[Trevorthetractor]

No I am not sure, just taken off the off side trumpet today and found a broken spacer? Just below the diff housing but can’t see any teeth off the crown wheel so tomorrow will dismantle the diff assembly, although I don’t see a spacer in the diagram.