I have a customer with a 2004 2500 4x4, cummins. When driving at highway speeds(60-70mph) if you hit a small bump or undulation in the road the truck goes into a violent shimmy. It fels like the front wheels are going to come off. It does not happen all the time but when it does look out. The customer has been to the dealer bu they told him it ws probably the road. Yeah right! When i drove it and it happened to me i wanted to jump out because you literally lose control , until you can slow it down to a stop then take off again. Any idea's... ????