Just happen to be 1400 km from home in a different country with limited internet and I think I have a gearbox issue.

W114 ambulance, has had a 300D motor installed, so possibly a non original gearbox, four speed manual.

It has developed a grinding noise when revving low, in first and second gear. Once the revs are up, back to normality.

Could this be a symptom of low gearbox oil, it does leak oil a little from somewhere ?

And, haven't been able to find with slow searching on the internet, how does one top up the oil, I've located what looks like a 17mm or so hexangular "alan key", bolt half way up the side of the gearbox, would that be the one ? No sign of a dipstick.

Thanks in advance