The most common cause of the shakes under braking is warped rotors. It is a common thing that can usually be taken care of by having the rotors turned. Start there and put on new pads and see if that doesn't clear up your issues.
A forum community dedicated to Ford F150 owners and enthusiasts. Come join the discussion about troubleshooting, performance, tires, wheels, lift kits, modifications, classifieds, maintenance, and more!