Submitted by Roy Cail.

Yes, this could be one of the issues causing a car to shimmy.  A loose ball in the front wishbone can be one of the causes of front shimmy.  The front end caster ( 5 degrees) is dependent on the exact position of the front radius ball.  Make sure you have all the correct pieces to mount the radius ball to the bottom of the flywheel housing.  It should consist of an upper and lower cap, two spacers that fit through the mounting holes in the lower cap, two springs and two castle nuts.  If the assembly is correct and the ball does not fit tight, purchase or make a shim out of a thin fender washer, pounded to fit around the top half of the radius ball and reinstall the cap assembly.  Then measure the front end caster.  Also make sure the tie rod balls are round and the drag link ends are screwed in tight enough — check Les Andrews Mechanics Handbook for specific settings.  Toe-in should be 1/16″ to 1/8″.  Also make sure the mounting bolts for the steering gear box are very tight.  Worn king pin and/or bushings can contribute as well.  All these things relate to front end shimmy.  The most over looked cause is incorrect front end caster adjustment.  This is determined by the position of the radius rod ball.