Hi Scotty. I have a 92 Olds regency that pulsates while braking just at the start of applying the brakes and then goes away. Front rotors do not have grooves and are not warped or too thin. The rear brake shoes are also new and adjusted. Drums are also smooth and in good shape. My anti lock brake light is on although I just replaced both front wheel hub assemblies and the wiring was done correctly for the sensors. Is this an ABS issue or something else? Im not sure what else to try. Are there rear ABS sensors in the drums that could be bad?? Thanks.

abs systems failing often do that, but more often it's just worn out brake rotors that are warped. You would need a run out dial gauge to check that correctly, you can't eyeball that