  Violations of the $\Delta$I=1/2 rule are investigated in the nonmesonic weak
hypernuclear decay using a weak $\Lambda$N$\to$NN transition potential based on
meson exchange. While the weak $\Delta$I=3/2 matrix elements of baryons with
pseudoscalar mesons are known to be very small, the same matrix elements of
baryons with vector mesons, evaluated in the factorization approximation, are
found to be significant. Within the uncertainties of the factorization
approximation we find that the total rate increases by at most 6% lying within
the error bars of the more recent experimental result. The neutron- to
proton-induced rate, on the other hand, can change by up to a factor of two,
while the asymmetry parameter is strongly affected as well.
