On Tue, 29 May 2001 05:45:26 -1000 "Hope Peter" <hope_peter@bah.com>
writes:
> What I have always wondered is...what causes this pressure?
> Is it the heating cooling/expanding contracting thermal dynamics
> thang? Or
> is it something to do with petroleum breaking down.
>
> Pete
My understanding is that the pressure develops as everything warms up and
the air inside the diff / swivel ball/ tranny expands. Regular breathers
enable the pressure to escape, I guess air makes its way back in as the
thing cools. Raised breathers enable a more rapid (and more complete)
equalization of pressure, which becomes more important when you wade and
thereby rapidly cool your diffs, for instance.
Raised breathers are also much less prone to clogging, tho' not
completely immune. Ask my friend Travis, who thought he heard weird
noises coming from his rear diff and decided to check the oil level in my
(heretofore clean--yes, this is foreshadowing) driveway. His oil level
was fine, and his raised breather had somehow clogged--he got a facefull
of oil, and I got a nice puddle on the driveway. It was pretty funny.
bill
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