Gear shifting problem

[columbiers]

Hi, hoping someone can advise with this:
I cannot shift from 5th to fourth, at all, it just won't go in. All other shifts are fine. If I go from 5th to third I can then go into 4th from 3rd no problem.
I have greased the gear selector on top of the box, no difference. If the engine is off I can go from 5th to 4th no problem.

Thanks for any help

[johnnyroper]

Being able to shift 5th to 4th when engine is off proves linkage etc is ok.

I would also say clutch is fine as other gamers are ok,sounds like a synchro issue to me.

[columbiers]

Yes I thought synchro too, but was hoping not!
I've changed the gearbox for a secondhand previously, last year. Not sure I want to do it again. Given the age of the car it night be time to say goodbye 

[mike wilson]

Tried double declutching?

From fifth into neutral, lift the clutch pedal and rev slightly, dip it again and into fourth.  Try it stationary at first, until you get the technique.