My shifter started popping out of 5th gear.
Its happened to others and theres plenty of searchable material as to why this happens(wear caused by constant pressure on the shifter.... like a hand). The usual remedy is simple....find another transmission from the junkyard to source a suitable 5th gear gearset.
Since the 5th gear is readily accessible through the 5th gear cover, you dont need to pull the entire transmission to get whats needed. You do need a breaker bar a 36mm socket a 26mm socket and a roll pin punch to remover the main gearshaft nuts and roll pin for the 5th gear selector fork.
But how do you recognize
a suitable replacement
I hadnt read a description of what to look for nor seen pictures of the issue at hand.
Since I had a spare transmission to work with I took a look at the 5th gear clusters to see what the issue was......
The area you need to look for is the teeth on the clutch hub and the teeth that they will mate with on the primary 5th gear.
See how the teeth have been flattened on their left side?
Heres a shot of the same teeth on the replacement gearset. Note that they are in much better condition.
Here is a side by side shot of the teeth of the 5th gear clutch hub. these teeth would be facing "down" (in towards the transmission) whereas the teeth on the primary 5th gear would be facing "up" (towards the 5th gear cover).
You can see the worn teeth on the left clutch hub and how much gap has been created in the assembly.
Pretty worn, beat up and generally unhappy teeth in the clutch assembly
In this shot the clutch hub teeth still have a well defined profile.
Ill take a guess and say that the teeth of the primary 5th gear are built with a bit of reverse taper to be able to have a good mechanical friction with the teeth of the clutch hub. Once the taper gets worn out theres little to have them interlock together and the shifter then pops out of gear.
So thats it then. If you are having issue with 5th gear...this is the issue and this is how you recognize a worn 5th gear from not worn.