Truck shakes/vibrates when braking.

Check your tire pressures, too high pressure can cause vibration from the tread when braking. Also check for a deformed or separating tire. Another thing to check would be the condition of the front suspension, loose parts could set up a vibration. Did you get new rotors or get the old ones machined? It's possible a rotor was not set up straight on the lathe and is not running true, causing vibration.

99% of the time it will be the rotors that are warped.