need help diagnosing

Check the transmission fluid, but it sounds like the trany is done for.

Transmission fluid is good. Oil level is good. When I could drive it in 4x4 auto, I had no slippage. But the moment I released the gas I no longer had power to go forward or back wards. Just rpms.

Smell the transmission fluid. If it smells burn, there is a problem.

Send some of that warm weather toward the Mid West...You'll have to get this to a transmission shop for proper diagnosis.

Lol it is nice and sunny here.....there is no burnt smell to the fluid and it still looks like transmission fluid (I had a previous used vehicle that I almost bought that transmission fluid was almost black - needless to say I didn't get it lol ). Don't have a lot of money to do trial and error type of thing. I'm reading that it's either tranny or the transfer case that controls the 4x4 auto, 4x4 high and 4x4 low

Check the transfer case fluid level and look for metal particles in it.

It could be a pressure solenoid of some sort, problem is on this sight we all know symptoms and a course of action to take. None of us are transmission re-builders, thus asking someone at a trany shop, And hey, it just stop snowing here, got dumped on with 3". Tomorrow sunny and 50° and then some.

New symptom: park won't engage. Dash Baird says it is but have to throw e brake on to keep it in place.

Well, just have to see what is going on down there. Also, not sure if it is tied in with this problem or not, but there is a shift interlock system on this that is tied in with the brake light switch. And Ford did have a problem with there transmissions coming out of park at one time.

Well got the diagnoses. Transfer case broke.

Makes sense, I should have thought of that. Glad you found the problem.