probably brake rotors and pads.
Most common cause of that is the rotors are out of round are warped. REPLACE ROTORS.
go to following link you will get the answer: http://www.wonderhowto.com/how-to-replace-brakes-2003-f150/
check and replace tires and tie rod ends as neccassary
Rotor and drums are out of round, need turned, probley just the rotors. Be sure to replace the pads and shoes too. You said it is bouncing. If the body is bouncing then the shocks are bad and need replacing.
I am sorry there needs to be more info.on this....are you saying when you have the flashers on and apply the brakes that the hazard lights go out??
The power brake booster is leaking vacuum and that makes the engine die when the brakes are applied. Replace brake booster.
You have a warped brake rotor(s). Resurface or replace the effected brake rotors.
The Vehicle shakes because of the virbration produced by the engine at the stop sing
If it shakes only when the brakes are applied, its the brakes. Just because they are "good" and stop the truck well doesn't mean they are balanced and wont cause a vibration.
ABS means either Antilock Braking System or Anti-Blockier System, depending on where you live. (What it does: if you stomp really hard on the brakes, it will rapidly apply and release the brakes for you, keeping you from skidding out of control and crashing.) If the ABS light is on in your Ford truck, that means the electronics that control the anti-lock part of your brakes are not working, and you need to take the truck to a mechanic.
1. you need to check your brake fluid. If it is TOO low, then no brake fluid to help stop the vehicle. 2. You need to get new brakes.
I had the same issue on my Sierra 1500 and it ended up being the rotors, take your truck to a brakes specialist or any other place you take your vehicle for a brake inspection and its most likely your rotors are warped meaning bent out of shape.