Why does the (steering) wheel wobble?

[ericrayl@nameless.com]

The patient in this case is a '86 4kcsq with 158k mi.

The symptom is a shimmy or oscillation in the steering wheel noticable
only when in the process of turning the wheel, and from about 5 to 40
mph.  The oscillation frequency changes with speed (so it isn't the
rack, I guess) and above 40 mph is high enough to not be noticed.  Tires
have been balanced and rotated front to back, symptoms remain unchanged.

Is this a CV joint going South?  Anything else come to mind?

While I have your rapt attention, Is there anything else I should
likely be replacing on this car to return it to or improve upon it's
original reliability or performance.  Other than maintenance items the
only things I have done to this car are:  Timing belt and water pump,
front lower ball joints, mufflers, thermal switch, and alternator.

TIA,
Eric Rayl
ericrayl@nameless.com