front left wheel vibrates when braking.

How do you know it is the front left?

if 4 by 4, could by c/v joint. could also be warped disks or a binding caliper. if so suggest upgrade of disks to drilled and slotted. you get better heat dissipation. this will allow you to pack heavier loads with out over stressing the breaks. they last longer. if you do one side you have to do the other.