Loose steering wheel

[Bpnmrice@domain.elided]

Here's one I haven't seen discussed on the digest yet. I encountered a rather 
unnerving condition on my ride home from work today. I noticed that my 
steering wheel was rotated about 10 degrees off center while my Spider 
tracked straight ahead. It has always been dead center before. 

While stopped at the next stop light, I placed pressure on the wheel in one 
direction, and it rotated further, though the front wheels remained pointed 
straight. When I started moving again (probably a dumb thing to do), the car 
continued to track straight and true, though now the steering wheel was 
nearly 180 degrees from where it should have been. I limped home carefully, 
and now my beloved Spider sits in the garage while I ponder what to do next. 
(Everything else about the steering seems crisp with no looseness or wobble.)

Now that I had the night to sleep on it, I checked the steering system a bit 
more carefully. With the steering theft lock engaged, the steering wheel 
would still rotate, though with some amount of resistance. I removed the 
wheel itself and found that the bell-shaped housing that it attaches to 
rotates under the large nut at the top of the steering shaft. I guess that 
means that the wheel assembly is not properly engaging the steering shaft (or 
whatever it is called). I suspect that this is a result of pseudo maintenance 
performed by the PO. Here are my questions to fellow digesters.

  - How does the steering wheel assembly (the hub the wheel attaches to) 
engage the steering shaft? Is it a spline or something else?

  - Since it appears that the steering wheel was removed once before, is it 
possible that it was reinstalled improperly?

  - How can I tell if the wheel is far enough on the shaft to engage whatever 
it takes to hold it in place?

 - What size is the nut the holds the assembly on the steering shaft?

I don't have my CarDisc yet, and Pat Braden's "Bible" doesn't give enough 
information about the steering for me to figure this one out. Any suggestions 
out there? What could allow the steering wheel to rotate on the shaft like 
that? 

This is a 1986 Spider Veloce that appears to be stock (including some very 
dried out leather seats). I welcome any and all ideas.

Bob Rice
Tampa
bpnmrice@domain.elided

------------------------------