I thought I was being clear about the distinctions between gear oil and
engine oil when I said "50 weight gear oil or an equivalent weight engine oil."
The base oils themselves are identical, the difference is the additive package.
Stick to gear oils if you feel you must, but the automotive industry as a whole
has abandoned that practice, for the reasons I already outlined. As too has
the agricultural industry, where they have been back dating lighter fluid
recommendations for tractors build as long ago as the 1930's.
If you really want to amuse yourself with oem fluid recommendations
and Laycock overdrives, just look at Volvo. They run the range of
30weight gear oil (try to find that!) to 80/90 weight gear oil for the
D type, and 80/90 weight gear oil to Type F&G ATFs for the later J
type.
Lyacock had their own recommendations for the oil selection of their
auxiliary transmissions. But this was often times ignored by the vehicle
manufacturer. It's a tribute to the robust nature of the Laycock
transmission that it tolerates the variety of oils it is subjected to by
the many vehicle manufacturers.
There is a company in England that claims to be staffed by ex-Laycock
employees. http://www.overdrive-repairs.co.uk/
Since I can't find where I found or saved the scanned image of
a Laycock paper specifying oil type, I figured asking these folks
would be the next best thing. Maybe first best thing, since oils
and technology have changed substantially in recent years.
I'll post their reply to the group when I receive it.
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