The only differentials that lock the wheels together when you try to hand turn them are ones that are preloaded, either with an interference fit in the clutch packs or with coil springs. However, helical diffs normally don't fall into this catagory. The Phantom Grip provides the spring preload. Unfortunately, it doesn't give the differential any clutches that the springs normally compress in a typical LSD, so the effectiveness of is, um, sort of a Phantom...
