tranny filler plug thread size

[camsaure]

I am not at home at the moment, but am restoring a panhead kicker cover that has the filler plug bored out and threaded for a much larger pipe plug. Hard to find another with the right date code. My plans are to sleeve the hole back to standard with an aluminum tube heliarced in the hole. I will most likely need to order a tap to rethread the hole (pretty sure I don't have one at home). Does any of you know the size tap I would need to order? Thanks, Cam

[kg993]

7/8-18, but that may make for loose fitting threads with some plugs. But I've never tried a tap. I like to make blind hole sleeves (gives a surface to press with) threaded a couple thousanths oversize then press in with .006" interference and bearing/sleeve loctite. Face the top down flush with good gasket surface and it'll stay till someone torques it with a pipe wrench.

[camsaure]

Thanks for the reply, I think you method is an even better option. Thanks again, Cam