croc Posted April 9, 2009 Share Posted April 9, 2009 According to the manual for the Explorer the front axle, gearbox and transfer box use OMD 330. But what is it? The translation says that it is SAE 50 oil but I think that this may be incorrect. The only thing I can find on it from past threads is this; omd330, which is a sae50 engine oil and often specified for gearboxes, it is equivalent to a straight 90 gear oil, the calculations for sae gear and engine oils worked out on a different scale. There are two SAE scales, one for gear oils and one for engine oils, that overlap. SAE 50 is in the top end of the engine scale, but is the same viscosity as SAE 90 in the gear scale. The difference seems to be the additives added to the base oil to make it most suitable for engine, straight gear or EP gear oil. If OMD 330 is specified for gearboxes why would you use SAE 50 engine oil rather than SAE 90 (non EP) gear oil? Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted April 9, 2009 Share Posted April 9, 2009 If OMD 330 is specified for gearboxes why would you use SAE 50 engine oil rather than SAE 90 (non EP) gear oil? Croc, The simple answer is this, there was no straight 90 gear oil in use in the Services. Often military oil grades are kept to a minimum to simplify supplies. My recollection is that OMD330 was used in a lot of vehicle gearboxes, probably because they contained non-ferrous metals and also because synchros do not work at their best with extreme pressure additives present. I have never seen any gearbox damaged through use of SAE50 engine oil. Quote Link to comment Share on other sites More sharing options...
thor698 Posted April 9, 2009 Share Posted April 9, 2009 Croc, The simple answer is this, there was no straight 90 gear oil in use in the Services. Often military oil grades are kept to a minimum to simplify supplies. My recollection is that OMD330 was used in a lot of vehicle gearboxes, probably because they contained non-ferrous metals and also because synchros do not work at their best with extreme pressure additives present. I have never seen any gearbox damaged through use of SAE50 engine oil. isent SAE50 engine oil the same as SAE90 gear oil:confused: thats what the old chap told me who i got my oil from:) Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted April 9, 2009 Share Posted April 9, 2009 isent SAE50 engine oil the same as SAE90 gear oil:confused: thats what the old chap told me who i got my oil from:) It is of nearly equal viscosity, but not the same oil. Quote Link to comment Share on other sites More sharing options...
croc Posted April 10, 2009 Author Share Posted April 10, 2009 Thanks Richard that makes sense, also explains why I can't find a military reference for SAE90 (non EP) If the only reason gear oil wasn't used was that it wasn't available, is there any reason not to use SAE90 in place of SAE50, as I would have thought a gear oil would perform better for the application? Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted April 10, 2009 Share Posted April 10, 2009 If the only reason gear oil wasn't used was that it wasn't available, is there any reason not to use SAE90 in place of SAE50, as I would have thought a gear oil would perform better for the application? Croc, I see no reason not to use a straight 90 gear oil where OMD330 is specified. Quote Link to comment Share on other sites More sharing options...
croc Posted April 10, 2009 Author Share Posted April 10, 2009 Thanks again Richard, that is the conclusion I had come too but it is good to have a second opinion. What different flavours of oil have been put in it over the last 58 years is anyones guess though... Quote Link to comment Share on other sites More sharing options...
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