Well, finally I had the car repaired, the problem was the broken pinion, had one teeth broken and other ready to follow. I found an used unit, complete and with low wear. Got all the bearings, spacers and seals new, and my mechanic which some years ago assembled differentials for a local fiat dealer did the work. Run 25 kms this afternoon and no noise, no vibrations, nothing. These are the old and new parts....
Broken pinion:
![](http://i62.tinypic.com/msznec.jpg)
Old differential with loose planetaries:
![](http://i60.tinypic.com/2el49qd.jpg)
The "new" one:
![](http://i57.tinypic.com/2znn7dl.jpg)
Very hard to find 9/40 gear ratio:
![](http://i62.tinypic.com/30tt1e9.jpg)
Have no pictures of the replacement differential, but it was exactly the same as the old one.
Edit: I found some pictures from the seller:
![](http://i60.tinypic.com/16jf1vm.jpg)
![](http://i62.tinypic.com/i2rccl.jpg)
Tomorrow I'll go more kms and see if it was worth the time and money spent to find this used part. You can get dozens of 10/41 and 12/43 brand new and at very good price but this 9/40 one seems to be very elusive....