Leaky diff from the filler plug..

[analog_me]

I know it has been discussed before but until now I have still not understood what is causing a leaking filler plug on the sierra diff.
Also and mostly how to solve this?
I have read threads where people suggest to align the filler plug with with the hose on top of which it is sitting but i checked mine and the plug seems to have no marks indicating the need for properly aligning it. It just a piece of teflon machined to fit the hose on top of which it is sitting.
Of course i can disconnect this an install a vent hose which i will take to the top of the rollbar, that should for sure fix it bit is not the way to do it.
Any advise welcome.
Thanks

[DCL]

Firstly, it we're talking a Sierra diff, then I'm guessing we're talking about the vent rather than the filler plug. If so, most diffs will vent some oil when driven hard, particularly on tracks with left hand corners. Fitting a tube may not stop this (it'll just works its way up the tube) - the best way to stop it is to fit a catch tank to the vent.

[analog_me]

Hi Dave

yes you are correct i meant to say vent and not filler..
Why should some diffs leak and some not.
why is the there a plug if this doesnt work well and if catch tank is preferable.
is there a point in better sealing the cover so it doesn't leak?
could there be something wrong with my setup i could fix?

Edited by analog_me on Thursday 18th March 19:10

[DCL]

One problem in the Caterham is that the angle they are mounted is not the same as Ford cars. In the Sierra the prop shaft slopes down and the diff is tilted more back. In the Caterham they sit more nose down. This tends to mean they are overfilled in the Caterham - if you fill them by quantity, or jack the car until they sit level (or slightly nose up) they tend to vent less oil.

[analog_me]

DCL said:

One problem in the Caterham is that the angle they are mounted is not the same as Ford cars. In the Sierra the prop shaft slopes down and the diff is tilted more back. In the Caterham they sit more nose down. This tends to mean they are overfilled in the Caterham - if you fill them by quantity, or jack the car until they sit level (or slightly nose up) they tend to vent less oil.

Many thanks Dave, this has been most useful,
I will start by fitting a catch tank as you suggested and monitor the leak as the oil level drops,
I will take it from there