Posted by Sherman in Idaho [72.47.153.61] on Friday, February 27, 2015 at 17:32:27 :
In Reply to: Tap Size for Tranny Drain Plug? posted by CSCameron [71.223.243.161] on Friday, February 27, 2015 at 15:53:55 :
Most older American gearbox drain and fill plugs are 1/2" iron pipe thread. Either a regular pipe plug with a square nub, or a flush plug with a hex or square hole in the end will work. Bear in mind that 1/2" pipe is about 7/8" OD, so you'll measure the outside diameter of the whole at about 7/8". If the threads are buggered up, the cheapest pipe tap you can get will be fine for "chasing" them since cast iron is easy to cut and you won't need to cut much of it. Don't try to just force a plug in, though, because it will probably leak and it's no fun at all trying to get a stuck plug out. Pipe dope is necessary for a good seal.