It was the right hand one, the long one in other words. They all seem to break this one, the shorter one never seems to break. I found a complete 1400 bakkie diff on a scrap heap, I stripped it, and apart from dirty oil the diff and shafts were still good. In fact the bakkie shafts are a whole lot thicker all the way to the splines, where the 1200 ones tapper of. Didn't even bother changing the oil, my diff's run probably less than 5000 k'd with the oil it had, since I locked it a month or two ago, just pushed it through a sieve and put it back in. Will add some Wynn's for good measure. Running the open diff from the bakkie for now, 'tiil I can sort out the M75 with a LSD.

Interesting thing though, the 1200 diff had 35 teeth on the big gear and 9 on the pinion, giving it a 3.88 ratio. The bakkie one had 43 and 11 respectively, giving it a 3.90 ratio. Not much difference, but I am wondering why they would use more teeth on the bakkie one. More teeth probably means more material to wear down before you run into trouble, although non of the ones that came out of my car has shown any wear...

So my car is now running with a gearbox and diff from the same scrap heap...