  Let $F_n$ be the free group on $n\ge 2$ elements and $\A(F_n)$ its group of
automorphisms. In this paper we present a rich collection of linear
representations of $\A(F_n)$ arising through the action of finite index
subgroups of it on relation modules of finite quotient groups of $F_n$. We show
(under certain conditions) that the images of our representations are
arithmetic groups.
