When I switch to 4hi or 4low, and make a turn, it feels like the system is binding. The truck actually wont even move unless you give it a decent amount of throttle and/or straighten out the wheel. If you're already moving and make a turn, this "binding" will actually slow the truck to a stop.
All my new era fords have done this. Even an old 74' F-250 shop truck we had did this. Its all of what everyone has said. Its NORMAL for it to bind while in 4X4 mode. Your working all the drive points against each other. As you move fwd and turn, the front wheels, one or both depending on your axle type will work against the rear because they are not rolling in the same plain with each other. When the wheels are turned the force of the driving action is side ways to the rear wheels. When your in 2 wheel drive the front wheels turn at different ratios to each other and its fine because they are NOT connected to the rear drive axle in any way.
In 4 x 4 you have now tied atleast 3 axles together especially if the rear is locked or is a locker type. You turn more than say 5 or 10 degrees off straight on hard surfaces and you start to feel the effects. If you try and turn sharp on dry or grippy surfaces and gas it you can actually feel the truck try and almost hop as it shudders and turns! This is just the nature of the beast. NORMAL in my opinion. All my fords from my 94 ranger to my 98 F-150 04 FX4 and the Raptor. All have had P trac.
Do this and listen and it will give you a little more of a sensation of whats going on. Roll your windows down. Engage the electric lock rear end and make a tight circle at a slow speed. CRUNCH, slip, gravel slipping sounds will abound. The wheels will be fighting each other because they are now locked as a solid axle and the out side tire will be being dragged around the outside as the inside wheel acts as the pivot point. Watch a semi trailer being backed at an angle by the tractor. The trailer wheels all see forces from different angles and just grind away at the ground and each other. Same kinda thing.
Also, from way back, I am old remember, I always try and back up 10 or 15 feet after I disengage the 4 x 4. This will help asure that everything has disengaged from each other. All the drive dogs have backed away or out of their slots. Same thing if you have the bind as you discribed, just disengage the 4 x 4 featur and back up, straighten the wheel if ya can. Then proceed fwd. This should relieve any bind.
I have for years and still do engage the 4 x 4 when it wet out. I love being able to BLAST away at lights, drive through water without near as much hydro steer and I feel my braking is way better because it ties the front and rear together and does not allow the wheels to brake at different ratios, I E brake bias is reduced.
WOW! I have a typing cramp now. HAhahaa. I say totally Normal.
BDRAG