Was having some serious thunking going on recently when taking off hard on dry pavement. Now I'm getting a high frequency vibration between 48-56mph. When you let of the throttle it stops and as soon as you get back into it the vibration starts again. Just started doing that this weekend while I was pulling my snow machines back from the cabin. Was thinking carrier bearing for the thunking and maybe for the new vibration. It's an '02 F350 psd crew cab short bed.