hello im a newbie to this forum and to fiats got a 900 chento and the gear change cable went got a second hand one but when i took the old one off it was connected to a big lump held on with a circlip that i removed when i went to put it back on the shaft it had sank inside the casing and when i try to pull it back it seams to be on a spring that want let it stay out while i refit the big lump what do i have to do to refit it . thankyou very very much if you can tell me

I think you are describing the selector.

Just remove the cable from the selector, it just pops off, and fit to your own selector.

Cheers

SPD

sounds like the problem I had.
There should be a small hole in the shaft, you can use a woodscrew with the tip snipped off to turn into the hole and pull the shaft out. you can then slip the 'chunk of metal' (triangular right?) over it and tighten it (three hands would be usefull!)

thankyou for yiur help . managed to get the swine on and im back on the road now