Worm Wheel gearbox - Pressure build up

I have an application where I am employing a worm-wheel gearbox in which I am using a grease of '01' or '00' consistancy and i am getting a pressure build-up after a few minutes of running and the grease is migrating through the ballrace and potentially into the motor... I have introduced a small ptressure release hole to help, but this made no differrence.. I am using lip seals worm-wheel shaft but am a little hesitant to put them on the worm shaft, due to increase friction (which is already near the limit for the application).. Does anybody have any 'black magic' ideas to improve my situation. The motor-gearbox should act as a sealed for life package, which should last the life of the final product.

Thanks,
roozle

Highest Regards,
Roozle