Hey guys
Is it possible to switch a single action tie rod hydraulic cylinder to a double
action ? or do i need a diferent piston with seales on both ends! Thanks for
your advice Bill.

You might need a different piston, or might not. If the cylinder ends have the ports already in them, I would remove the breather plug and plumb it up for a try. Lots of the newer cylinders have a seal that will work in both directions.

Two things prevent you from making a double acting cylinder out of your single acting cylinder. First is that the piston seals are usually chevron seals and unless you have them back to back, they will only hold pressure one way. Second is the outboard seal on the piston rod. On a single acting cylinder, the piston rod seal is not built for the pump pressure. It is usually more of a dirt wiper and it is most likely to blow oil out of it if put under pressure. The best bet is to replace your single action cyliner with a double acting cylinder. If you are into redesign, you can do anything.

Sometimes double acting rams have been used in single action applications by simply venting the stem end port . if that is the case plumb her up and away you go
most cylinders made exclusively for one way action have a stem diameter close to the same as the bore to lessen the venting action