my 2000 f350 ,will not lock in or shift in 4 wheel drive .not sure if its shift motor or vac.. lines .but question is with that being said ,should't it lock in at hubs by hand even though auto fly not
if the 4x4 lights are coming on and you can hear the transfer case lock in then it should work with the hubs in the lock position. if the lights are coming on and you hear the transfer case lock in and 4x4 doesnt work with the hubs in the lock position then you have a bad hublock or something at the specific wheel end. if the lights come on and the transfer case doesnt lock in then you likely have a bad shift motor... if no lights come on the you have a bad shift motor or other wiring problem. i have seen all of these, with your truck i have seen corroded wiring near the driver side shock tower, which causes no 4x4 and no lights....
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