600w gear oil for '39

[cxgvd]

I recently purchased a lovely '39 Century Model 61which was driven just 40 miles in the past ten years.  Over the winter I am going over the chassis and engine and hope to use it as a touring car.  I have drained the gear oil from the rear axle and transmission and plan to add varsol to flush them out before adding new lube.  At last the question is should I buy 90w for both axle and trans or can I use 600w which I have for my older Buick axles and semi-fluid grease which I use in my 1913 and 1915 transmissions?  I would think oils have been covered to death in the forums but never with this nuance.  Thanks, Gary

[Bob Engle]

90 w will be fine.  The 600 weight came from early cars with nonsynchromesh  spur gearing.  Just be sure to NOT  get the new GL5 fluids.  They contain compounds that are not compatible with brass and copper.  CRC makes a 90 w GL4  differential lube.  It drives me crazy that as the government and auto industry  keepsforcing changes to these automotive fluids that they do a poor job of covering the compatibility with antique cars.

 

Bob Engle

[Larry Schramm]

You can buy GL1 from Tractor Supply.  It is the gear oil used in the Ford 8N tractors from what I have been told. It is just plain oil.

[Daves1940Buick56S]

GL1 is fine for the transmission but with the hypoid gears in the rear you really should use a GL4 in the diff. Although I suppose that a GL1 from today probably beats any EP oil from 1939.

 

 

[cxgvd]

Hello all;  I bought a gallon of 85/90 which says it is compatible with GL3, GL4 and GL5.  I plan to take a bit of it and drop a piece of brass and copper into it and let's see what happens.  Many months until spring.  Regards, Gary

[Daves1940Buick56S]

Gary: it's not like it corrodes the metal, exactly. What happens is there is a sort of shearing effect as the metal interface with the oil in between. The GL5 will end up taking layers of molecules off the brass and copper. Basically for your trans it means that you will be wearing out the syncros at a much greater than normal rate. Read the attached.

 

Cheers, Dave

 

 

Transaxle_oil.pdf

[Dave_B]

Gary,,

 

For the transmission Pennzoil has a product called Synchromesh. It is GL3 and is made for use in manual transmissions. It should work well and is sold at Advance Auto stores and probably other parts stores.

 

For the rear I would use the regular 80-90 gear oil for hypoid gears. I don't think there any brass parts in the rear so that is not a concern there.

 

Cheers,

Dave