I'm bouncing in my F150

I have a 1999 F 150 with 130,000 miles. Without notice the backend began to “bounce” at about 40 MPH, no problem below or above 40 MPH. What is happening?

If these are the original shocks, they are WAY overdue for a change. The good news is that they’re shocks and shocks are far cheaper and easier to change than struts.

Check for a big lump on one of your tires