This is what I hear. Retro fitting may not be worth it since the non trd axle is not the same as the trd axle, getting an ARB locker may be better. It can be done but may be unnecessary as far as work and time put in. As far as non selectable lockers on ice and slick stuff it is because you will break loose easier and the back end has a tendency to be all over the place. It can be remedied by driving style but odds are if you are in snow and ice conditions a lot it is better to have a selectable locker. You will also get faster wear on the rear tires.