^ oh its the rear? damn... makes it harder... but pipe wrench is still the way to go
front coilovers and rear coilovers are the same design on our cars. i dont see how that makes it harder.
as for the op. use a pipe wrench. it grabs pipes, which is basically what the bottom sleeve is. you also might want to find something to hold the shock still, since the sleeve is seized, the shock will turn as well when you try to turn it.

