After about 27000 miles, I was driving down I476 at approximately 55-65 mph. It was on a stretch of road with occasional ridges and on hitting one of them, the steering began to vibrate more and more. It eventually resolved itself as I slowed down to around 40 mph. This happened on a number of occasions under much the same conditions and I took the vehicle into Videon, a local Jeep dealer. They immediately replaced the steering damper as they claimed it was worn. I do not have the old damper, it was retained by Videon. I feel that had the road conditions been any less than dry and offering good grip, the vehicle may well have become uncontrollable as the shimmy was very violent. The steering on this vehicle has always been vague but I put that down to the relatively antiquated design of the Jeep and the fact that our other car is a Subaru which is very precise.