You are right in assuming that the only sources of oil dripping from
the cotter pin are rear engine seal or front gearbox seal.
Odds are that it's engine oil. The rear seals are notoriously difficult
to get right, particularly if there is wear because of loose rear main
bearing allowing the crank to move as well as to rotate. That the crank
was cracked and vibrated could have allowed the movement.
Why would it be dark? My guess is that some of the color is the
chewing of the rope gasket there with, perhaps, some aluminum from the
oil thrower, Moss #433-410 (external engine page of catalogue).
Does it have a distinct smell? Most gearbox oils do have a sulphur
smell to them. The gearbox should have been filled with 90w or equivalent
gear oil, which would give it the thickness you mention.
Whatever the source, separation of the gearbox from the engine will
be necessary in order to fix the problem. MG was aware of leaks in this
area, hence the cotter pin. We like to think that the oil leaks were
designed in to keep the cotter pin from rusting.
> This stuff is very dark/dirty-looking, and both the
> engine oil and the gear oil in the transmission are clean.
> (To me, this oil looks too "thick" to be engine oil,
> but we have yet to take a sample to someone who might
> be able to tell us for sure.)
> Jiggling the cotter pin increases the flow to about one
> drip per second, and enough oil has collected after
> much less than 1 hour of running the engine at idle
> to keep the drip going for several minutes.
> As neither fluid level is too high, we think that
> we have either:
> a) A rear main engine seal leak
> b) A front main transmission seal leak
> Both nasty enough problems to force us to drop the
> tranny down to fix the problem before doing anything
> else (how ELSE might any sort of oil get into that area?).
> We do not recall EVER seeing any oil dripping from this
> point before the rebuild (years of driving, including
> the "Lap of New England" rally/parade/Bataan Death March
> with a successful climb up New Hampshire's Mt. Washington.)
> But a search of the archives and FAQs yelled this semi-cryptic
> gem from a 1999 posting by a Mr. Bob Howard
> in response to a question about a TD shaking when backing up:
> > There is the possibility of oily clutch.....
> > one hopes not..... Is the cotter pin in the clutch
> > housing free to jiggle and keep the drain hole open?
> Which supports the impression that oil is EXPECTED in this area
> as a "normal" event. (Why else would the hole and cotter
> pin be there? To drain off condensation?)
> I am not a big expert on TD specifics, as I drive an '72 Midget.
> Anyone have a clue to lend before we rent a tranny jack
> and drop the tranny?
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