I need a chuck assembly this old drill the chuck does not un-screw it is on a geared shaft the gears come off but the chuck is attached to a long shaft with splines and lock rings

If you have a model number for the drill, there may be an assembly diagram at SearsPartsDirect.com. Most drill chuck spindles are either threaded or tapered. Jacobs Chuck Technical Support: Chuck Removal and Installation discusses both types and is generally applicable to other brands of chucks. I haven't seen a lock ring type chuck on cordless drills, could you post a picture?