My 01 f150 supercrew not engaging. Ive had forever i know how to use it. When i turn to 4 hi the light comes on but only back tires spin. Took down road running about 45 turned shifter did feel the little jolt like always but when i pull over into snow i stop and hit it only back tires spin. Ive checked fuses cant find anything. Please any ideas i would like to find problem tonight. THANKS DAVE

Ok i just checked and found that when 4x4 on the front drive shaft is engaging cause it wont turn. Is there some kind of selonoid or something that locks up front differential to engage front shafts