Any Explanation?

[DRUDOLPH148006]

I just bought my first BMW in S. California and trailered it home to Klamath falls,
Oregon at an elevation of 4100 feet. Somewhere during the last 30 miles from
home, gear oil began leaking from the vent hole on top of the rear axle carrier.
After refilling it, it has not leaked again. Anyone have an explanation for why
this may have occured? Would the change in altitude without the shaft turning
cause this, could the vent tube facing a certain direction create a suction strong
enought to pull gear oil up more than 3 inches? My guess is that at least a pint
of oil leaked out. Thanks for any ideas.

[PGlaves]

I just bought my first BMW in S. California and trailered it home to Klamath falls,
Oregon at an elevation of 4100 feet. Somewhere during the last 30 miles from
home, gear oil began leaking from the vent hole on top of the rear axle carrier.
After refilling it, it has not leaked again. Anyone have an explanation for why
this may have occured? Would the change in altitude without the shaft turning
cause this, could the vent tube facing a certain direction create a suction strong
enought to pull gear oil up more than 3 inches? My guess is that at least a pint
of oil leaked out. Thanks for any ideas.

Air was entrained in the oil - maybe with a little moisture. When the atmospheric pressure dropped the entrained air caused it to burp. Not very common but I've seen it before - even on a bike being ridden.

I doubt it burped a pint - or it would have been nearly empty.

[DRUDOLPH148006]

PGLAVES, Thank you for the explaination, After going to look at a measuring cup,
it was more like a 1/2 cup that came out. I guess it was like opening the cap
on a bottle of soda after shaking it up.

[PGlaves]

PGLAVES, Thank you for the explaination, After going to look at a measuring cup,
it was more like a 1/2 cup that came out. I guess it was like opening the cap
on a bottle of soda after shaking it up.

Pretty much the same. If you haven't done it, I think it would be worth the couple of bucks worth of oil to drain out all the old oil and put in new oil. This is because there might be a little moisture in the oil which increases the tendency to entrain air.