Overfull transmission

The vehicle in question is my daughter's 1991 Honda Civic with a
5-speed manual. I was replacing both driveshafts yesterday, and before
draining the transmission, I removed the filler plug to check to see
if the last outfit who worked on it --a neighborhood service station--
had filled it to the proper level. I was sent scrambling for shop-rags
when about a pint of oil came out.

The remainder of the oil which emerged when the drain plug was removed
was quite dark, not black but definitely a dark grey-brown. I suspect
that this means engine oil has found its way through into the
gearbox.

So my question is, how common is this symptom, and how much of a
problem is it? The car has 325,000 km on it and uses a liter of oil a
month, yet has no problem passing its annual pollution check for
hydrocarbons. There are no oil stains on the pavement where it is
parked every night, but that oil has to be going somewhere!

 

It should be to the fill plug when the car is LEVEL.

They use "engine oil"

A " liter of oil a month" doesn't really tell us anything. The car might
be driven 1 mile/month or 5000 miles/month. The first scenario would
produce a tremendous amount of smoke (if it would even run), while the
second wouldn't be visible.

 

It was level.

But surely not USED engine oil. Would you expect transmission oil to
be dark a month after it was replaced?

1200 miles per month

Quote: "yet has no problem passing its annual pollution check for
hydrocarbons. There are no oil stains on the pavement where it is
parked every night,"

Now can an overfull gearbox leak oil only when in motion? Because that
would explain where it's going.

 

akaik, there's no possible fluid connection between engine &
transmission - the only bit that connects the two is the clutch bell
housing, and that's dry.

oil can "burn" if the valve stem seals are worn - that never shows up on
a smog test because it only happens when coasting downhill, a situation
not simulated on the test.

 

==============
John

A PCV stuck open will (invisibly) suck oil out of your crankcase like
crazy. It gets burnt, but it could eventually cause catalytic converter
troubles.

'Curly'

 

That gearbox actually is supposed to be full of motor oil. But unless you
saw what the service station guy put it, you can't really draw conclusions
about the color. My guess would be that someone at some point filled it
with gear oil instead of the motor oil it is supposed to have and the
remnants of that are mixing with the oil.

 

A liter in 1200 miles is right on the edge of what Honda considers
acceptable. With 325,000 km on the car, things are warn and are not sealing
as tightly as they once did. It is likely a little bit of oil is being
drawn past the rings and valve seals and being burned. I wouldn't worry
about it unless the oil consumption gets worse.

 

I don't see how engine oil can get into the transmission - any oil which
gets past the rear seal is going to fall down to the bottom of the bell
housing and out the vent hole... possibly wetting the clutch plate on its
way. Used oil, even from a trans is hard to judge by color - it could have
been quite dark when new and some use could make it slightly more opaque.

With case side filler holes it's not unusual to overfill and not let drain
back fully - with a forced pressure feed up from below, and with a hose
fitting which is almost a plug fit in the filler hole, when the overflow
starts you could easily be a pint over filled. If the mechanic didn't let

Well I'd do the usual check by following the car when the driver lifts off
the gas and lets the engine overrun - any smoke will tell how much leakage
you have past rings or valve seals. On our '90 Civic, there were never any
oil drips/stains but it had a leak from just around the area of the oil
control jet at the cylinder head gasket. The rear of the block was always
wet but whatever was leaking never made it to the floor - burned off by the
exhaust or swept back under the car when moving.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??