The B1 piston assembly is not easy to remove and then reinstall. Because of the length of the two big springs behind the cover, it takes a tool that has a long throw. Some have used valve spring compressors, blocks of wood, and pry bars, and some work, but not easily, because most do not have the travel needed to move the cover plate back into position so it stays straight. Watch the video below to see the full operation by Kent. NOTE: The reason this tool will not work on the 722.4 is that the bolt thread size going into the transmission case is smaller

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Look at the travel required.
Much easier to get it out. Getting it back in without this tool to keep it aligned can be challenging.