BMW Diff Output Seals Leaking - Three year update

[Geoff Brown]

It is three years & 10,000 miles since I changed my cars BMW diff output seals.

It was three years from new (2013 -2016) & a similar mileage when the original seals started to leak so I thought that an 'anniversary' update was due.

Since the change the output seals have remained robust without even a hint of leakage. And that is with the oil level up to the fill plug. After much debate about oil levels does this throw all the theories of having a lower level out of the window?

In my opinion several factors have determined why the replacement seals have not leaked:

• a subtle difference in the lip seal design
• a more robust metal flange which could resist flexing
• the new seals positioned further in to the casing as far as they could go against the originals which were almost flush with the outer rim of the diff seal housing
• new seal position being more inboard could have reduced the wear effect upon the lip seal caused by shaft rotational variation.

As in the full thread on this subject Caterham Cars have always been aware of this problem but it has now fallen off the bottom of their to do list.......?

If only the Caterham drive shafts had been adapted to connect to the original BMW diff drive attachments that have to be forcibly removed on the build then I believe that there would be no leaks. 

The full thread can be found here:

https://www.lotus7.club/forum/techtalk/bmw-differential-have-you-had-oil-leaks-output-seals