I have an 89 MJ, was moving my truck last night on some ice. My friend was out side and said when my back tires spun on the ice my front wheels didnt move. The day brfore when i used it it felt like it started working (better traction in the snow). Is there an easy way to tell if its working? Maybe see if front drive shaft is spinning, or could front be spinning and 4WD still not working? Thanks