  Physical evolution of cosmological models can be tested by using expansion
data, while growth history of these models is capable of testing dynamics of
the inhomogeneous parts of energy density. The growth factor, as well as its
growth index, gives a clear indication of the performance of cosmological
models in the regime of structure formation of early Universe. In this work, we
explore the growth index in several leading $f(T)$ cosmological models, based
on a specific class of teleparallel gravity theories. These have become
prominent in the literature and lead to other formulations of teleparallel
gravity. Here we adopt a generalized approach by obtaining the M\'{e}sz\'{a}ros
equation without immediately imposing the subhorizon limit, because this
assumption could lead to over-simplification. This approach gives avenue to
study at which $k$ modes the subhorizon limit starts to apply. We obtain
numerical results for the growth factor and growth index for a variety of data
set combinations for each $f(T)$ model.
