D21 gearbox problem

[oldboy]

Hello everyone I have a question I'm sure you guys can help with I have a D21 89 diesel 5 speed dual cab Navara and the gearbox has developed a problem when using 3rd gear to slow down to corner it makes wizzing noise like the gears aren't meshing and when going up gears and engaging 4th there is no drive at all but 5th gear is fine. Does this mean the box has gone past it's use by date or can it be saved? Thanks for your time

 

[Dion]

If there's no drive in fourth it needs new dogs and synchros. Rebuild.