Pulsing in Park

Recently, within the last month I have noticed that my 93gc has a very distinctive pulse to reverse. It is engaged in park, with the engine running , a seems to tick back wards in a rythum, as if almost in reverse. I have 176k with a 249 NPG, 4.0 , I have never noticed this before. Is this part of that recall I recieved notice for in the past months? Or is it just a adjustment needed after so many "GREAT MILES"?