PROBABLY a warped brake rotor, but there could be other problems that cause that. make sure that all your suspension components are torqed to specs. you can get the specs from the lift kit manufacturer. get your alignment checked.
It is likely a brake rotor has to much run out (warped). There could also be some problem with steering or suspension components.
Warped rotors
roters need turned. 65;
Warped brake rotors.
You need an alignment.
You have a warped rotor. It must be trued at a machine shop or replaced.
You need the front rotors machined or replaced.
Most likely warped rotors
Need more info like what is the vehicle doing when it shakes, is it idling in park, driving down the road, braking, driving at highway speeds, etc.
try haveing tires rotated and balanced, check for worn suspension and steerign components. does brake pedal pulsate when braking? out of round brake rotors can cause a shake in front end , or could be a caliper hanging up
The braking problem is almost certainly a disk brake rotor. The vibration could be a faulty tire, a bent or damaged "half shaft" or an out of balance tire. Front end vibration is not caused by an alignment problem, but can be accentuated by worn suspension or steering components.
Uneven application of braking power at high speeds, caused by the heat that is made between the rotor and the brake pad; this is causing uneven stresses in the rotor. Such heavy brake usage aggravates the situation by providing uneven wearing along the circumference of the braking surface. However, other possibilities occur with loose suspension ortire wear; i.e.wheels out of balance.