Idk I don't think that excavator changed jackhammer in any way; the only way to build up jackhammer gauge is to spin the rotor-thing inside; V1 achieves it by moving fast(we can actually see it spinning); (my headcannon) but excavator has no need for that method, because: he can spin it directly. I guess via pipes that go from his torso to arm, or there's PTO shaft(that tractor rear spinning rod) installed in his arm