Guys!
Honestly; If U are in doubt as to 4.3 or 4.1, then give it 10 turns in the power input flange...
It`s not rocket-chemistry...........
For anyone wondering, it is actually dead easy with the diff on the truck (bit more creativity required if testing on the bench). I did it for the first time:
1. raise a wheel and support, centre diff unlocked, gearbox neutral;
2. put a mark on the raised tyre (helpful to have something on the ground next to it as a reference point);
3. put a mark on the diff pinion flange. Make a temporary reference point to take the guesswork out. I used a bit of metal crocodile-clipped to the pipework below);
4. Turn the tyre twice while at the same time watching the mark on your flange and counting;
5. If after 2 turns* of the tyre, the flange has rotated 4.1 times, your diff is 4.1:1;
6. If you want to be really anal, measure the diameter of the diff flange with a tape (350mm IIRC), divide by 10, and that's the length of .1 rotation... There really is a lot of difference between .1 and .3
* It has to be two turns because of how diffs work. One wheel on the axle is stationary, so the other has to go twice as far to get one rotation of the crownwheel.
