This box was rebuilt a couple years ago with new 2nd/3rd gears, new 3rd/4th synchro assembly (both inner and outer), new layshaft cluster gear and new needles. Since then 3rd speed has been unusable. It’s out now and I’m trying to get as much useful information as possible before I tear into it further tomorrow.
My suspicion is that the fellow who did the work either assembled the synchro parts in the wrong orientation, or he slid them onto the shaft in the wrong orientation. There is also the remote possibility that 3rd gear or the synchro sleeves are just bad parts.
This is how it’s behaving. Screen left is the front of the box and 4th gear, right is towards 3rd gear. Note how it behaves differently.
Am I correct in my understanding that as the fork pulls the synchro back towards the gear, the syncho should spin up, before it finally pulls the outer operating sleeve off of the detente on the inner synchro sleeve to engage with 3rd gear? This is what it does when I shove it forward toward 4th gear. But there is zero friction when it is slid back.
Are there any other tests or checks I should perform before tearing it down to find this or other problems? I haven’t noticed any issues with 1st, 2nd or 4th.