  Non-decoupling effects related to a large $m_t$ affecting non-oblique
radiative corrections in vertices ($Z\bar{b}b$) and boxes ($B$-$\bar{B}$ mixing
and $\epsilon_K$) are very sensitive to the particular mechanism of spontaneous
symmetry breaking. We analyze these corrections in the framework of a chiral
electroweak standard model and find that there is only one operator in the
effective lagrangian which modifies the longitudinal part of the $W^+$ boson
without touching the oblique corrections. The inclusion of this operator
affects the $Z\bar{b}b$ vertex, the $B$-$\bar{B}$ mixing and the CP-violating
parameter $\epsilon_K$, generating interesting correlations among the hard
$m_t^4 \log m_t^2$ corrections to these observables, for example, the maximum
vertex $Z b\bar{b}$ correction allowed by low energy physics is about one
percent.
