I’ve now got a copy of the gearbox pages. Just about anybody can swap a part out but I’m not about to buy a new gearbox and don’t trust second hand ones. The workshop manual gives the specifications on the diff which as you suggest if you don’t know how to use a dti gauge then don’t try to repair the old one.
So for anyone who is interested what I have found is that the LH Planetary Gear could be moved when it should be held in position by the bearing and the lower satellite gear. As I probed it actually dropped into the housing. I will strip it down just to find out exactly what failed but that explains the knocking on lock.
Interestingly the E-learning pages list this problem but I’ve never come across it before. Fiat also sell a repair kit for the diff which at around £150 seems a better option than an unknown second hand box which could have the same problem.
The right hand drive shaft seems to have got quite hot at some point but is ok, I would hazard a guess that excessive loads are what has caused the pressure plate fingers to fail but it could just be coincidence. The clutch otherwise has no wear but is being replaced with a complete Valeo 3 piece new item.
When I dismantle the box I will see If I can take photos of the offending parts and hope there’s no additional damage otherwise I’ll have to do the same with a replacement unit.
