Well I put the new relay on with the same problem. I called ford and talked to a mechanic. I explained my problem. He explained to me the brake had to be on for it to shift in 4 low. And they're had to be a signal to get power to come to the t-case. I shut the truck off with the switch in 4 low. Started back up and t-case was 4 low. And was driving in for low.
Switch to 4 hi. And it worked. To my amazement. So I have a problem in the t-case. Is also may a low roaring sound. Soni priced a used t-case and should be picking it up later this week.