You don't say but if it's an E4OD then the TC nuts are 13MM, a six point socket is better to use, at least that is what I have used on the last four I've done. They are self locking nuts and should never be re used. Just why are you changing the TC? If it has blown up then you better pull the pan, and your aux cooler, if you have one, it will possibly be full of junk also the cooler coils in the radiator.