How many axles does a quad dump truck have?

Five, all told. The steer axle isn't included in the count, so a single axle with have two - a steer and a single drive axle, a tandem will have a steer axle and two drive axles, a tri-axle will be a tandem with an additional lift axle, a quad axle will have two additional lift axles, a quint will have three additional lift axles, and a centipede will have four additional lift axles. A superdump is usually a quint with an additional Strong Arm mounts to the top of the dump body which extends out to maximize the vehicle's wheelbase.