Possibly the USS Franklin, an aircraft carrier that was devastated by Japanese kamikazes off Okinawa in the last months of WW II. They had to strip the anti-aircraft gunmounts off the sides to get it to fit in the canal & locks. I believe it was towed to NYC.
On the Panama canal site it says that the USS New Jersey that was recently towed through the canal was the heaviest vessel ever to transit the canal. I would have to think that the difference between the Franklin and the New Jersey would be the armored hull on the battleship.