> > John Esposito at quantumechanics.com says that detergent oils should not
> > be used in an OD because they foam.
> ========================================================================
> I know of about 5 rebuilders that recommend nothing but hi-detergent
> multi-viscosity oil for O/D's and some say they use Mobil 1, so different
> strokes for "FT"
The reason gear oil is normally non-detergent has nothing to do with foaming
... the 'detergent' action in oil is to keep dirt and wear particles
suspended in the oil. That's desirable in a system with a fine filter, like
a car engine, since then the dirt and wear particles are trapped by the
filter and removed.
However in a gear box with no oil filter (or only a coarse filter like an
A-type OD), it's more desirable for the particles to settle out, so that
they aren't constantly being recirculated past the wear points.
Non-detergent oil will allow the gunk to form sludge, which in this case is
actually a good thing.
Note that the "racing" oil I've mentioned is a low-detergent oil (since it
normally doesn't stay in a race engine long enough to form sludge anyway).
It also has a high level of "anti-wear" additives that function the same as
"extreme pressure" additives to some extent. IOW it almost is gear oil, but
without the sulfur-based additive found in conventional GL5 (and GL4) that
supposedly eats brass synchro rings, thrust washers, bushings and OD
clutches.
Randall
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