Reg Evans Posted September 13, 2015 Report Share Posted September 13, 2015 I'm going to change the fluids today in my recently purchased 1939 Chrysler Royal with an R7 overdrive and my owners manual recommends SAE No. 70 aircraft engine oil or just SAE No. 70 engine oil. Is this just a single grade non-detergent oil or what ? Why won't regular 80W90 gear lube work .....same stuff that goes in the rear end. Thanks Quote Link to comment Share on other sites More sharing options...
TodFitch Posted September 13, 2015 Report Share Posted September 13, 2015 I think the viscosity number standards for oil and gear lube are different so SAE70 oil would have a different viscosity that SAE70 gear lube. I've never heard of SAE 70 engine oil so I don't know where you would get it. I think I'd be calling a major oil company and asking for a applications engineer to talk with. They should be able to find out what a modern replacement for an old rated oil is. Quote Link to comment Share on other sites More sharing options...
T120 Posted September 13, 2015 Report Share Posted September 13, 2015 (edited) This GL-1 gear oil is currently listed on ebay..GL-1 means that it contains no EP additives and it is safe for use in the older transmissions. The differential does require EP additives.. I have also posted a chart showing the relative viscosity of engine vs gear oils.This is the limit of my knowledge on the subject,I would follow the recommendations in your manual. http://www.ebay.com/itm/GL1-140-wt-Gear-Oil-Mineral-Oil-Gallon-2-each-/251464637379?hash=item3a8c75dbc3 Edited September 13, 2015 by Ralph D25cpe Quote Link to comment Share on other sites More sharing options...
Reg Evans Posted September 14, 2015 Author Report Share Posted September 14, 2015 Thanks guys. A guy on the Chrysler forum found this on eBay so it's on its way to me now. It's Aircraft engine oil SAE 70 just like my manual calls for !!! Quote Link to comment Share on other sites More sharing options...
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