98 Dodge Ram 1500 Quad Cab short bed, 5.9L engine V8... slow speeds my truck slows down and stops, but at 55 miles per hour and over and need to stop like now it won't, had brand new rotors, new break padsput on and the truck still doing same thing!
Anyone know of a reason why this is happening?

 

have you bled them?

 

Sounds like a power booster issue. Maybe a bad vacuum line running to it.

 

do you feel the abs kicking in? did you flush the lines and put in new fluid? sounds like you have air or mositure in the lines that is compressing under hard braking...