All wheel drive - front diff - oil change

[dlipka]

Hi - I removed the oil today from the front diff. As I undid the fill plug, there was a hissing sound as air either entered or escaped from the diff. This suggests to me that the vent / bleeder is blocked. The housing is also damp with oil which appears to have come throught the shaft seals - which would be understandable if the diff the became pressurised as the oil heated up....

Has anyone experienced this before?

Has anyone changed the bleed valve before?

Thanks,

Derek

[wwest]

Hi - I removed the oil today from the front diff. As I undid the fill plug, there was a hissing sound as air either entered or escaped from the diff. This suggests to me that the vent / bleeder is blocked. The housing is also damp with oil which appears to have come throught the shaft seals - which would be understandable if the diff the became pressurised as the oil heated up....

Has anyone experienced this before?

Has anyone changed the bleed valve before?

Thanks,

Derek

The VC itsself is ALWAYS hermetically SEALED so it is entirely possible that the design Porsche uses has the entire VC "case" fully sealed. Some VC's even have an inert gas under pressure inside the case. Gas "bubble" is used to delay the onset of VC coupling. So there may not be a vent/bleeder.

Motto: If it aen't BROKE then DON'T fix it.

[goldenwarrior1]

The front diff and the VC are 2 separate units. Pulling the drain plug on the front diff only drains the front gear box. The VC is sealed and uses a very precise amount of silicone based oil and is not intended to be serviced. I went back to the Porsche service manual and it makes no mention of anything other than the standard drain and fill for the gear box. Based on my experience, I would say your vent may be plugged as you suspect. Clear the vent, service the diff and and then monitor for any leaks after throughly cleaning while you have it open.

R/Tom