Maybe not on your gearbox, but on an 84 Uno 70s I had a linkage that I could never adjust properly. I put in new bushings and washers, adjusted till I thought it was right, but I could never get the lever to sit in the 3rd 4th gate.
Eventually I bought a 4 speed Sting as a parts car. One day Alex suggested I take the top off the box, the little silver cover over the linkages.
I discovered someone had been in my gearbox before, and put it back together without the washer in between the locator springs that are on the shaft. I stole the washer from my parts car, carefully removed the shaft in my Uno 70s just enough to slip the washer on, and refit the spring. I needed to be careful not to drop anything in the bottom of the gearbox.
Hey presto, everything was great. Like it was when it was new.
I had spent years fighting with the gearlever trying to find the right gear, in the end it was about a 30 minute job to fix it.:bang:
This car is a real mystery, when I got it it had a horrendous knock coming from he engine bay. The knock was so bad it wasn't serious!, as the engine went well. It was the top engine mount, that was put in 180 degrees out.
For years I also struggled to get it timed right, others tried and failed as well. Eventually I found it needed to be timed on plug 2, not 1. I think the flywheel has been messed with.
Anyway, I don't care now it is going fine, and when I get the gearbox out for its engine transplant I will find out.
It has 250000km on it. And when I get the rust out from around the sunroof it will be great, but that has been a task I have been going to do for about 10 years!