Gearbox Index Plunger Seal?

Upon assembling my gearbox after a rebuild I find that O have no "O" ring or washer to seal the index plunger housing. The Andover Norton site does no show any sort of seal for the housing.

How does one seal the plunger housing?

That might be the only part that doesn't leak on my gearbox. No gasket, no fiber washer and I did not use any sealant. Others will have other ideas.

I've never found one leaking but when I take them out, I put them back with yellow Teflon tape. IMHO, one of those "can't hurt" things. You definitely don't want anything that prevents it from screwing all the way in.