[Green Machine]

You can make a tool to get the rear piston out. Get half a muffler clamp, the formed steel piece, (not the u bolt) drill a hole in the center and use a bolt or chunk of threaded rod and drill a hole in a piece of wood or steel.

Put the clamp in the tranny, curved part to the rear, run the bolt out the back thru the hole in the wood block and tighten the nut to squeeze the springs down.