Recently my 2001 F150 4x4 has been very hard to turn when the 4x4 is engaged. Does anyone have an idea as to what may be causing this problem. Thank you...

 

Does it only get hard to turn when in 4WD?

U-joint(s) in your front axle shaft(s) may need to be replaced. Might be causing a little bit of binding when you turn if they are going bad.

 

Should also note that depending on the type of surface you are driving on it may seem harder to steer with 4WD on. If you are on harder, drier surfaces it will seem more difficult. If that is the case, you shouldn't be using 4WD in that situation as it can wear on the truck.