Granny Shifting, not doubling the clutch like you should

It's a fault I've never come across before. It's certainly not common.
As I understand what you've said, the car shifts up gears fine, ie; 1-2-3-4-5...but coming down 5-4 you get 'blocked' out of fourth? It's not grinding, it's just blocked so the stick moved as far as the neutral gate, comes across but will not move any further into 4th, is this the case? Or does it go into 4th but not drive?


I can think of two possible cause (within reasonably probability)

The likely cause would be the reverse gear lockout is maladjusted, loose or faulty. This mechanism stops the selector from going from 5th into reverse without going across the neutral gate to 'unlock' first. If it's not working preoperly it'll be locking out reverse and 4th gear.

Secondly, it could be the interlock that stops selection of 2 gears at once. If 5th interlock has a bit of shit under it it may not unlock 4th gear. Unlikely but possible.