'39 Royal R7 Overdrive Trans.

[Reg Evans]

I'm getting ready to change all the fluids in my recently purchased 1939 Chrysler Royal with the R7 Overdrive trans.

 

The owners manual recommends "S.A.E. No. 70 Aircraft engine oil" or to substitute  "No. 70 engine oil"

Is this what would be called today W70 non detergent oil er what ???

 

Any recommendations ?  I'm wondering why just regular 80W90 gear oil wouldn't work.

Thanks

Edited September 13, 2015 by Reg Evans (see edit history)

[Rusty_OToole]

Gear oil has additives that can louse up transmissions and possibly overdrives. On another board there was a thread by the owner of a 38 Nash. The transmission was hard to shift and prone to grinding. He drained the lubricant, which smelled like hypoid lube, and filled with straight transmission oil (no additives)  and it began working better. It seems the anti friction additives in the hypoid lube prevented the synchros from working. The factory manual recommends straight gear oil for the trans, hypoid lube for the rear axle.

 

Your case may be similar. The overdrive may need a certain amount of friction to work correctly. Go by the factory recommendation. No doubt their engineers had their reasons, based on thousands of hours and miles of tests.

[Reg Evans]

Thanks for your response Rusty !     I'd love to go by the manufacturers recommendation but can't seem to find SAE No 70 Aircraft Engine Oil or it's equivalent.  Any ideas ?

[Rusty_OToole]

Try your local airport. It is still used in some piston engines. Take a jug in case they only have it in bulk from a 45 gallon drum. Or, maybe your local auto supply can order it.

 

Or try Ebay

 

http://www.ebay.com.au/itm/VINTAGE-PENNZOIL-AIRCRAFT-Engine-OIL-SAE-70-The-Tough-Film-Cardboard-1-Quart-/262043245421

 

Or other online supplier. Try a web search.

[Reg Evans]

Thanks again Rusty !  I offered the seller $8 instead of the $12 he was asking and it's on it's way now. It takes 3 pints so I'm still searching for another quart.