what is making it stiffer?
1. If it's the stuffing tube that's making it stiffer, and it really is too stiff, I would just loosen the bolts at the top of the stuffing box. Don't worry, the boat won't sink while you're doing this, in fact, on mine I think the gland is above the water line, so it's just a splash-seal. Loosen them all the way, noting the initial torque, then bring them back down, just not all the way. Work the rudder back and forth. Better?
2. Maybe the steering cables are too tight.
3. Maybe there's an obstruction somewhere.
4. Maybe the steering gear was put back wrong, and a couple of cables are crossed incorrectly. Does it make any noise? A grinding sound, or feeling?
5. Below-decks autopilot drive unit binding, due to misalignment? Partially seized?