[Healeys] Fix for overdrive operating shaft oil leak

[Noel and Helen]

Hi listers

has anyone come up with a fix for the ubiquitous oil leak from the O 
ring on the right side of the overdrive?  I've checked the archives and 
Tech Talk and can't find a solution, would it be possible to either 
machine out the casing and  fit a lip seal (pretty hard to do in-situ 
I'd imagine) or can you fit a second O ring behind the operating lever?

any help appreciated
thanks

Noel S
Brisbane, Australia
BN1, BJ8