Jatco auto clutch drum thingy

Hi all,

Having a few problems with my freelander 1 td4 going from 3rd to 4th I think, checked the ohms on the plugs and solonoids all check OK, going to change the fluid butbit seems like it's the part on the non engine side of the gearbox that may be at fault. You take the plane off the end and a piston drum assembly comes off. Where in the UK can you get this from? Anyone got any links or pointers to getting it?

Thanks in advance

The drum is supposed to come off. What is wrong with it, is it cracked? Replacements are available. Need a bit more info to help!