I recently replaced my speedo with one from Ebay with a working Odo.  84
van..later model speedo now.  At first (for about 600 miles) it worked
really great, smooth quiet accurate to 1-2%   even though I couldn't get the
cable connection at the rear of the housing to "click-on" all the way.  Has
a white plastic lever (on the cable fitting) that is supposed to click over
a groove in the speedo and 'anchor' the cable in.. On the old speedo you
needed to squeeze that lever to release a little hook so you could pull out
that cable.
  The new one I installed, no matter how hard I push the cable and it's
housing onto the instrument, it won't click on...but that didn't seem to be
important to how the speedo and Odo worked until it got a bit cold (27f)
recently..It began making the noise in the Subject line of this post and the
needle of the speedo is now oscillating a little.  I've removed that
connection and put a little lube on the cable end and tried to re-insert it
with a little help from some long-handled needle nose pliers...still can't
get it to click on.  When I had the two speedos on the bench side by
side...I could detect no difference in the configuration of the female (on
the speedo itself) half of the connections..
  So should I just 'push harder'...?  Get a bigger "Pliers"?  Is there more
than one type of 'push-on' speedo cable or instrument?  Is there a 'trick'
to getting the connection correct...?
  Anybody hints?
  Don Hanson