Posted by Mike (Montreal, Quebec) on Thursday, August 31, 2006 at 11:05PM :
Gents,
I was browsing the archive and saw a post by Ken Dunnington in November 2005 where he said that oils used in old trannies and transfercases should not have any Extreme Pressure (EP) additives like most gear oils now have. He added some sources and reference s to the info.
I did some searches on the Internet and would like to share with you what I have found:
- Gear oils are classified with a grading of GL-1 (no EP additives) to GL-5 or 6 (most EP additives).
- GL-1 oil is used in transmissions and transfercases with bronze bushings and synchronizers. It contains no EP additives that contain sulphur which deteriorates bronze. The sulphur is what gives the oil it's distinctive smell.
- From what I understand in a transfercase (even if there is no bronze bushings), the killer is the heat that make the EP additives break down and clump into lumps thus decreasing the lubricity of the oil. We know our transfercases can indeed get hot.
- In a differential (3rd member) all bronze I know are beyond the oil seals thus would not be affected by the oil. GL-5 type oil is formulated specifically for hypoid gears teeth which move in a shearing fashion.
Here are sources I found of GL-1 gear oils:
- Shell Dentax 80W-90 (product code 436-005 in Canada and 59003 in the US in 5gal).
- Esso Marvelube 80W-90
- BP Gear Oil 90
- NAPA GL-1 90 Gear Oil (65201 in 1gal and 65205 in 5gal)
- Some Walmart stores are said to stock GL-1 oils
An acceptable substitute for GL-1 90 gear oil is SAE50 motor oil (such as Shell Rotella T 50). The SAE scale for crankcase oil is not the same as for gear oil; SAE90 gear = SAE50 motor.
A good technical paper on the use of oils in vintage vehicles can be found at the link at the bottom of this message.
I hope this info can be useful to others.
Regards,
Mike
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