Gearbox breather on 1850 single rail?

[Bumpa]

I know that gearboxes like to be vented to the air to prevent any pressure build up. Where is the breather on the 1850 single rail box? I would like to check that mine is clear.

[Richard the old one]

The photo is the top of a 1500 gearbox with Over Drive but the breather on a 1850 will be the same it is the small black round plastic bit that is let into the top plate.

[Bumpa]

That's interesting because looking down the tunnel from the engine bay that top plate on my car has some oil lying on it, and may be the cause of a small amount of oil dripping from the gearbox area. Assuming that oil has come through the breather, why would that happen? The oil level was only up to the bottom of the filler hole.

When I drained the gearbox the other day so I could get the OD solenoid out, the oil was very frothy. Is that normal? I'm using EP80 GL4 oil.