  In this note, we extend modular techniques for computing Gr\"obner bases from
the commutative setting to the vast class of noncommutative $G$-algebras. As in
the commutative case, an effective verification test is only known to us in the
graded case. In the general case, our algorithm is probabilistic in the sense
that the resulting Gr\"obner basis can only be expected to generate the given
ideal, with high probability. We have implemented our algorithm in the computer
algebra system {\sc{Singular}} and give timings to compare its performance with
that of other instances of Buchberger's algorithm, testing examples from
$D$-module theory as well as classical benchmark examples. A particular feature
of the modular algorithm is that it allows parallel runs.
