U-Joints Bad?

["Karl Theis" <kjtheis@hotmail.com>]

Question...
  my GT6 has developed a rythmic 'tick' dependent on road speed that I hear 
only when coasting to a stop, like 5 mph and slower.  It's coming from the 
rear of the car so I'm thinking it is a half-shaft
U-joint.  When I get under the car and check it, everything seems tight.  My 
question is - Is the only way to tell if a joint is bad is remove the 
halfshaft from the car?
   thanks,
   Karl Theis