Does the shimmy increase and decrease with the speed of the car or the RPM of the engine/drive train?
In other words:
can you reproduce the shimmy in any gear at different speeds (Ex: 1st gear @ 25 mph and again in 2nd gear at a higher mph)?
-or--
Does it start at a certain speed (ex: 70 mph regardless of what gear you are in)?
-or--
Does is stop/start in a speed range (ex: 50 mph to 70 mph regardless of gear)?
-or--
Does is start/stop in an rpm range (ex: 2000 -3000 rpm regardless of speed)?