  We prove the crepant transformation conjecture for relative Grassmann flops
over a smooth base $B$. We show that the $I$-functions of the respective GIT
quotients are related by analytic continuation and a symplectic transformation.
We verify that the symplectic transformation is compatible with Iritani's
integral structure, that is, that it is induced by a Fourier-Mukai transform in
$K$-theory.
