  We construct a model for the weak pion production off the nucleon, which in
addition to the weak excitation of the $\Delta(1232)$ resonance and its
subsequent decay into $N\pi$, it includes also some background terms required
by chiral symmetry. We re-fit the $C_5^A(q^2)$ form factor to the flux averaged
$\nu_\mu p \to \mu^-p\pi^+$ ANL $q^2-$differential cross section data, finding
a substantially smaller contribution of the $\Delta$ pole mechanism than
traditionally assumed in the literature. We also show that the interference
between the Delta pole and the background terms produces parity-violating
contributions to the pion angular differential cross section.
