I just replaced the steering box and all the rods from the box to the wheels to fox this problem, it did nothing.
Truck has 200,000 miles, if I hit a pothole with either left or right front tire, the entire front end starts shaking and it increases to the point the truck might break or wreck. It started at highway speeds like 70 when hitting a bridge seam, over a few hundred miles the speed at which the problem would start was lower and lower and now if I hit a pothole at 35 it will start this wild shimmy.
I think the entire differential is actually moving forward and backwards when I hit the bump and the mass of the diff bouncing off of whatever combined with the friction of the tires on the road provides the means for the oscillation to increase to critical mass.
What is worn out that could cause this to happen ?
I noticed that the differential seems to have some lateral movement to it when I turn the steering wheel left and right while parked and the front of the leaf springs move left and right opposed to the movement of the wheel, they are moving not in their mounts, but the mount itself is moving up in the frame where I assume it is bolted in with a rubber piece. Don't know if this movement is the problem or just a syptom of something else that is worn out like a sabilizer bar or something.
There is a bar that runs behind the front differential with a lot of bends in it that connects to a smaller rod on each end that connects to the frame, the main bar is connected to the differential via a mount with rubber in it.
The is also a shorter bar that connect the differential to the middle of the frame, this bar is on the right side only.
None of these is obviouly worn or loose.
If I drive very slow over a rough gravel road, I can hear and feel a slight banging as if something is moving and hitting its stops, I can feel it via the steering wheel slightly but the entire steering system has been replaced and there is no play in it at all.