[AT] Transmission oil, 90-wt?

[Dean Vinson]

I stopped at Tractor Supply this evening, looking for 90-weight gear oil for
use in a Farmall M.  They had some 2-gallon containers of various 80W-90
oils, and 5-gallon buckets of 90W oil that according to the label is
specially formulated for use in 1939-1952 Ford tractors.  It even says "Ford
transmission oil" or something like that on the label.   What's the deal
with that?  Why so specific to one brand of tractor?

I'd figured there'd be 5-gallon buckets of general purpose 90-weight oil, at
a relatively moderate cost per gallon.  I assume the stuff marked as Ford
transmission oil would be perfectly fine, but should I be looking for 80W-90
instead?

(I haven't mentioned this yet on the tractor list, but after seeing all
those Farmalls at the Portland show, I bought an M and am keeping it in my
garage.  Pretty decent shape, needs lots of tinkering.  Photo at
http://www.vinsonfarm.net/photos/1950_M.jpg).

Dean Vinson
Dayton, Ohio
www.vinsonfarm.net