Is GS the mid-cage or short-cage? If it is the mid-cage, it will work fine. (I didn't even know about the 37T difference capacity.) (Just looked it up, I see that it is.) Several of us here have this kind of setup. It works fine. (I have one wheelset with a SRAM 11-36T and one with Shimano's newer 11-34T cassette. Both shift without issue.)