Longitudinal weak gauge boson scattering has been well-known as a powerful method to probe the underlying mechanism of the electroweak symmetry breaking sector of the standard model. We point out that longitudinal weak gauge boson scattering is also sensitive to the gauge sector when the non-Abelian trilinear and quartic couplings of the standard model Z boson are modified due to the general mixings with another Z' boson in the hidden sector and possibly with the photon as well. In particular, these mixings can lead to a partially strong scattering effect in the channels of W(L)(+/-)W(L)(+/-) -> W(L)(+/-)W(L)(+/-) and W(L)(+/-)W(L)(-/+) -> W(L)(+/-)W(L)(-/+) which can be probed at the Large Hadron Collider. We study this effect in a simple U(1) extension of the standard model recently suggested in the literature that includes both the symmetry breaking Higgs mechanism as well as the gauge invariant Stueckelberg mass terms for the two Abelian groups. Other types of Z' models are also briefly discussed.