3320 easy to turn but won't steer

I have a zetor 3320. When I turn the steering wheel the wheels turn left and right fairly easily but will not steer the tractor left or right. It's like there's no grab to the front wheels. This hasn't always been this way just recently started doing this. I checked the fluid and it was a little low so I added but it still won't turn the tractor left or right going forward or in reverse. Any ideas?

Under the dashboard is a splined shaft with a rubber disk. Either one of them is broken.

Hi
If the traktor dont steer vhen the vheels are tuned over the diflock is on.
Bjarne