You should have a transmission specialist check it for a problem in transfer case? I could not really find any info for your vehicle but looked up something similar with the following service bulleting from Ford. Maybe you just have the wrong tire size or low on air pressure?
Various 1997-2008 vehicles equipped with either 4 wheel drive or all wheel drive and equipped with control trac may exhibit a shudder on acceleration/deceleration, binding in slow speed turns or noise from the front driveline and/or transfer case. The shudder/binding will occur with the vehicle being operated in the awd/auto 4x4 mode. The shudder/binding may be due to incorrect tire circumference or improper tire inflation pressures.
Follow the Service Procedure steps to correct the condition.
Note this does not apply to 2006-2008 mountaineer with a 4.0l engine or 2007-2008 explorer and sport trac with 20 inch wheels.
Note vehicles on the list may require replacement of tire/s if the tire circumference average between the front and rear axles are outside of the 1/2 inch specification or if the tire circumference from side to side on either axle exceeds 1/2 inch difference, the smaller tire(s) must be replaced.
Note review the warranty and policy manual for ford motor company tire replacement warranty before performing the service procedure.
Note only use replacement tire and wheel that are the same size, load index, speed rating and type (such as p-metric versus lt-metric or all-season versus all-terrain) as those originally provided by ford. The recommended tire and wheel size may be found on either the safety compliance certification label or the tire label which is located on the b-pillar or edge of the driver's door.
Note on some 4wd models, the initial shift from 2wd to 4wd while the vehicle is moving can cause a momentary clunk and/or brief ratcheting sound. These sounds are normal as the front drivetrain comes up to speed and is not cause for concern.
Review the tire label for correct tire size and tire inflation pressures located at the B-Pillar of the driver's door.
If the tire size does not match the label, this procedure does not apply, follow normal Workshop Manual (WSM) diagnostics.
If the tire size is correct, ensure tire pressures are within specifications.
Raise the vehicle on the hoist, refer to Workshop Manual, Section 100-02.
Disconnect all wiring going to the transfer case and road test.
Is the shudder/binding present?
If the shudder/binding is still present, do not continue with this procedure, continue with WSM normal diagnostic for 4X4.
If the shudder/binding is gone, proceed to Step 7.
Raise the vehicle on the hoist and reconnect all the wiring previously disconnected.
Using a tailor's tape or flexible measuring tape and measure the circumference of all four (4) tires and record the measurements.
Calculate the average of the circumference of the two (2) front tires and calculate the average of the circumference of the two (2) rear tires. (Figure 2)
If the difference between these two averages is greater than 1/2" (12.7 mm), front to back or side to side, replace the smallest circumference tire(s) and remeasure the tire averages. Refer to WSM, Section 204-04 for tire replacement.
Let us know how it goes and hopefully it is nothing major going on with the transfer case or transmission?
Sunday, June 4th, 2017 AT 2:19 PM