Pulling to right hard

1994 C2500 suddenly started pulling to right. It was pretty noticable before. I figured I would wait to check into it since I was getting some new tires. New tires came and after I put them on it now pulls harder to right. But sometimes it dont pull so bad. I seen no visible wear in steering components. No bad tire movement when I raise the vehicle.

I tempted to move the wheels with both in air at same time. I guess I should try one at a time.

Anyone know how to tell when the gear box is going bad?

Need to get this fixed before it wears out my new tires.

The tires seem to be straight. Ball joints seem ok.

ball joints can look ok but still be bad--idler arm and/ or pitman arm are common problems with these trucks- also check wheel bearings. How many miles on vehicle?