Brakes

[Lexicon]

This situation is most likely caused by a faulty wheel sensor. These little devices measure the indicator ring rotation as brakes are applied and wheels are in motion, the moment it picks up a non-rotational state, it activates the ABS valvebody and removes the pressure from the caliper and frees the wheel to spin enough to promote correct tire grip and eliminate slide. What do you mean by brake upgrade? If you failed to bleed the system correctly you could be getting a priming error from the ABS control module. This little sucker sits on top of the ABS motor and valvebody (frontside of passenger front fenderwell next to the radiator). Two areas to check:

Brake system pressure and bleed starting from RL RR LF RF
Wheel sensors, located on backside of indicator disc that run behind the actual brake rotor. The Ford Manual suggest in such events as axle removal that a new sensor be put in and this requires some use of a press to be correct in its alignment and sealing.