Gyroscopic force would be produced when a still-spinning wheel had its axis of rotation (i.e. angular momentum vector) changed. All the while port and starboard retract simultaneously in a mirror sense, this would not produce any effect.
But a spinning nosewheel retracting sideways, for example, as in the beloved Trident, would cause (by my calculation) a net yawing force on the airframe. Any Groundgripper drivers out there care to comment?