Transmission Gear Oil

Discussions related to motor & gear oils, greases, anti-freezes, etc.
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Transmission Gear Oil

Post by autoluke » Sat Aug 02, 2014 3:02 am

Are all synthetic gear oils harmless to the brass components in my 640 transmission ?

Don R's Cars
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Re: Transmission Gear Oil

Post by Don R's Cars » Sat Aug 02, 2014 8:01 am

Not sure about the synthetic part but I think it is the sulfur based EP additives that are the problem. I'm sure those with much more knowledge than me cab give a more complete answer. The other issue would be viscosity, an older transmission will need something like 600W, most modern synthetics are much too thin.
Don Rundgren
McKinney, Texas
1934 1100 Eight Sedan

Dave Czirr
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Re: Transmission Gear Oil

Post by Dave Czirr » Sat Aug 02, 2014 11:19 am

Can't answer your question about synthetics. The chloro-sulfur-lead compounds were used in early extreme pressure or hypoid gear oils and were harmful to brass/bronze but those additives have been absent from EP gear oils for many years, so any modern EP gear oil should be ok with regard to yellow metal. But why would you want to use an EP gear oil in a straight spur-gear transmission? I'd use whatever Packard recommended which was probably a heavy mineral oil, perhaps SAE 160 or 600. That said, I have used SAE 85-140 extreme pressure hypoid gear oil in both the differential and trans of my 34 for many years and never a problem but that's a very different trans with helical gears and synchros.

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Re: Transmission Gear Oil

Post by Adam » Wed Nov 05, 2014 4:33 am

Agree with Dave. A heavy non-EP gear oil like SAE 160 would be fine. I may have the original oil spec at home, I will check and report back when I get a mo.
"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

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