I've had vibration in my steering wheel just a little above idle on my
'77 Ford F250 PU for a while. I noticed the upper steering shaft
bearing seemed a little sloppy and the rubber boot at the floor was
shot, so I pulled the column out to examine it. When I pulled the
steering shaft out I was a bit shocked to find a deep groove cut all
the way around the lower end of the shaft. It seems the lower plastic
shaft bushing was worn enough to allow the shaft to shift downward,
and contact the metal clip that operates the reverse switch. This
hardened clip protrudes slighty into the inner column tube, which
rotates with the PRNDL to shift the trans. Every time the steering
shaft moved, this clip was cutting into the soft steel steering shaft.
Not a pretty picture. Seems to be a fairly common issue for this year
truck, as the first bone yard unit I pulled out to replace it was
beginning to have the same problem! I put a new bearing in a the
steering wheel end, and turned a piece of UHMW poly bar stock on the
lathe to replace the wimpy stock molded plastic bushing...Anyway maybe
with another 300K miles and 30 more years it would have worn all the
way through!