<VV> Hitch in Steering

[N. Joseph Potts]

My 66 has developed a subtle "hitch" in its steering that is evident at low
speeds and seems to occur somewhere around the straight-ahead position. It
is intermittent, getting worse (of course), and today made a very soft bang
or snap when letting the wheel turn past the point at which the hitch
developed.
     From the pitman-arm bushing out, the whole suspension/steering system
is new-ish. I include "ish" only to indicate that all these new parts not
long ago performed flawlessly, and did so for long enough that I really
don't suspect any of them, nor their installation. From the steering box to
the lower shaft bearing, the system is, as far as I know, virginal. I
replaced the top bearing (at the steering wheel) a few years ago. New-ish
stuff includes all bushings, ball joints, the springs, and tie rods
including ends.
     The behavior of the steering otherwise is perfect in all respects - no
shimmy or looseness. Except for the KYB shocks and 195/70R14 tires on 14x6
steel rims, the front end is all stock. Both have been in service long
enough that I don't consider them suspects.
     The idler arm is original, but I don't suspect it because the steering
is so tight (as noted above). Should I suspect it?
     My suspicions center on either the box or the coupling.
     Any suggestions as to what I should address first? Thanks.

Joe Potts
Miami, Florida USA
1966 Corsa coupe 140hp 4-speed with A/C