Q: Every time I droves 40 or 50 and apply to the brakes,my front end shakes what can this be

The most common cause for a pulsation when the brakes are applied is warped rotors. The brake rotors will wear over time and the brake rotors are a perishable item. The rotors can warp due to excessive wear, using the vehicle to tow heavy loads, or any other reason that will cause excessive heat in the brakes. It is possible that a fluid leak can cause a type of surge, but this will normally be observed at all speeds. Warped rotors are much more common than a leak. If the rotors still have enough material on them, they can be turned on a lathe, and the warp can actually be machined out. However, if the warp is too excessive, or the rotor is worn past its serviceable limits, they will need to be replaced. If you need help identifying and/or repairing the issue, contact a certified mechanic, like those available at YourMechanic.com.