Back and forth as in longitudinal to the shaft, forward and backward with respect to the car? Or side-to-side? I'm assuming very little movement means it's good and noticeable movement means it's time to replace.
Given the shuddering between 35mph and 45mph when accelerating anything more than soccer mom pace, I think I'm going to find a shaft in need of replacement. But I really appreciate the help confirming that before I tear it apart.
