I think you may have hit it when you say it was overfilled. I have a Flaming River reproduction reversed Corvair box on my T and am on the second one in two years. The first one dumped all of it's grease out of the same input shaft seal you are having issues with, to the point it got very stiff. I swapped it out for a new one with Flaming River, and the new box does the same thing.....red grease is coming out the shaft seal.

Flaming River really never had a good explanation to give me, which disappointed me somewhat. This second box seems to have finally stopped pumping grease out, so maybe it has reached the amount it wants inside.

I have sent you a PM with a guy on another forums address. He builds these Corvair reversed boxes and sells them, so he has a lot of knowledge about them. I didn't want to post his address on an open forum without his permission, but I'm sure he won't mind you getting in touch with him on a one on one basis.

Don