When switching into 4h the steering will begin to pull to the right. a vibration and humming noise gets stronger when increasing speed and getting really bad at 45mpr. then when trying to park backing up the whole system locks up. i have to put it back in 2 wheel to complete backing in. this is a 2001 sport trac

SOURCE: Front End noise and vibration

Check the U-joints and axle baerings. But its most likely because the truck is in four wheel drive.

SOURCE: 1992 Ford F-150 Ignition lock switch

Do you have a tilt wheel? If so you're only half the way there. The upper actuator is broken. And you got to get into the column further. As for the trick to get the cylinder in. Don't matter if you got a tilt or fixed wheel. Go to the top side of the column. About 2/3 the way down it you'll find the Ign Switch. A rod will be coming out of the top going towards the wheel area. Push it into the switch till the inst panel lights come on. That means that the Ign switch is in the 'ON' sopition. IE all the dash panel lights come on. There is a key on the tumbler that matches to a key in the ign gear. Than just incert the tumbler into the gear and turn it to lock it in.
If you got a non-tilt wheel then it sounds like the bottom of the tumbler is broken off and is still in the gear. If so do the same as above with the Ign Switch. That will align the key so you can take the broken part out and put the new Ign tumbler in.

SOURCE: stuck in 4x4 low

Have you tried backing up at least 10 feet .. If there is any driveline bind this would release it and allow the transfer case to "shift" ..

SOURCE: 1997 ford f250 steering problem

it could be the front axle u-joint binding up. i had the same problem, and that's what it was. i put greaseable u-joints on both sides.

SOURCE: Vibration in steering wheel

sounds like it could be the ball joints binding up