Steering Column movement

I've had the front end rebuild kit for my '78 308 for some time now, but was motivated to "git er done!" after I was playing with the car on an exit ramp, felt a "pop" in the front end, and the steering got loose/touchy... it was a slow and nervous drive home. I assumed I had popped a ball joint.

So last weekend I redid all the bushings (thanks for all the guidance on this list!), ball joints, and tie rod ends. Now while everything was at the point it needed to be done, I found nothing to explain the event or symptoms I experienced.

So before test driving, I decided to check out the steering column... when I poped the horn buttom (atfermarket Nardi on Momo adapter) I was shokced to find that the nut was loose and the wheel was loose on the shaft.

Now it doesn't appear that the nut actually loosened... it's almost like the whole colum moved backwards, making the nut no longer tight against the adapter.

I did not find anything with any apparent movement... and while it seemed like there was some slippage down below the bottom univerisal, I dnow think it was just the dimater difference making it seem that way.

I lightly tapped on the wheel center with a plastic hammer and it seemed to move forward a bit to where the nut was now snug-looking. A short low speed drive seemed to show no steering issues...

So where the movement coming from??

Thanks!!
Bill