The TC55 uses the same chassis as the 2120 one of Ford/New Holland's much successful longest production run tractors. I've run a 2120 since 1987 with no steering problems. Sure it steers harder than a smaller machine like a TC40/45 but that is due to the smaller loader and frame size. I don't know what is wrong with your steering, but since I have so many hours on a 2120 (since 1987), I decided to try out a couple at my local NH dealer. They feel just like a 2120 with or without a full bucket as you would expect. I will say that a 2120 with an overfull bucket (weight wise) does steer somewhat hard.
Andy