My 2009 ford f-150 4x4 headlights flicker. when I power up my window and apply brakes. Headlights really flicker when the limit slip kicks in. I have replaced the battery and alternator?

Chek your relays one could be going bad

Although my mustang did the same thing I feel that is an electrical issue with the traction control in the fords I am taking mine out and putting a different rear end in mine

Take a real close look at the battery cables and follow the cables and check for corrosion everywhere they have a connection. This includes the grounds. It is possible you have a loose or corroded connection somewhere causing high resistance and flickering.

Thanks Bob! I was thinking the same thing just wanted to bounce this question off people and see what they have to say! thanks again I will do that and let you know how I make out!

One should not have anything to do with the other. If Bob's suggestion does not provide positive results check the wiring hornace. The flickering you see could be caused by work insulation somewhere where wires come together in a package. An arc caused by bad insulation will cause a flicker in related components.