Should it take a minute or two for the abs to start working? the tires especially lock up in the rain for a min or 2 of driving and will also usually do it when dry too. i have replaced the sensor in the diff

 

no, there should be no delay. most of our trucks are rear wheel abs only, some are all 4.

when i start out some mornings with cold and damp brakes, the first touch or two of the brake pedal tends to lock the rears, but the abs kicks in and creates a chatter of lock/unlock.

as a test, at a slow and safe speed, stomp and hold the brake pedal. try it wet and dry to see if your abs is working right.

also check your rear brake shoes. see how they look.

 

yea thats about how mine is so i guess its fine