Checked the level yesterday and ended up wondering if the dipstick was too short! i.e. It just a drop of oil on the very end, well below the low mark. Topped it up and it took half a litre or so until it was just above full. Anyone know how low it has to go before things start getting damaged?

 

Half a litre low shouldn't be much of a problem.
I've found that you really need to be on a level surface to check the g'box level. Any slope and it's all over the place!
JohnD

 

JUSH....(EP)Extreme Pressure oils,That the gearbox uses,Are not like a conventional say engine oil,EP..Works by...Filling the gearbox "Full" with bubbles all the way to the top of the casting,And even further should an hole be present,Obviously,To a lesser extent,With the oil lower,But all the same,Some i feel..Would still get to the top of the gearbox,So total lubrication loss,i think...Would be perhaps extreme...But the oil level still has to excede the lower gear cluster,To be able to froth...Good Luck....Kev.

 

These boxes are easy to overfill as the are so long...which means that an overfill is harder to spot, and as John D says,they really need to be dead level to get the fill to the right level...

 

Thanks for the comments. I think my readings may have been slope influenced, will check again with the car level.