The non-linearity of the theory of gravitational moments often makes it difficult to understand intuitively. All fluid planets are likely to undergo differential rotation, which leaves an imprint on the higher order graviatational moments. To help up develop an understanding of how differential flow affects gravitational moments, we have developed a linear model that couples these two planetary properties and establishes a more direct and comprehensible link between them. We use this model to characterise the differential flow on Saturn and quantify the degeneracy in the flow properties given Cassini's gravity data. More details will be presented in paper that has been submitted for publication to Icarus.