  We report on the extraction of $\sin^2\theta^{\rm lept}_{\rm eff}$ and
indirect measurement of the mass of the W boson from the forward-backward
asymmetry of $\mu^+\mu^-$ events in the $Z$ boson mass region. The data sample
collected by the CDF detector corresponds to the full 9 fb$^{-1}$ run II
sample. We measure $\sin^2 \theta^{\rm lept}_{\rm eff} = 0.2315 \pm 0.0010$,$
\sin^2 \theta_W = 0.2233 \pm 0.0009$ and $M_W ({\rm indirect}) = 80.365 \pm
0.047 \;{\rm GeV}/c^2$, where each uncertainty includes both statistical and
systematic contributions.
