AWD problems

[Jim1761]

I have a 2006 Mercury Mountaineer, when the awd engages the left front wheel doesn't disengage. After driving awhile it will disengage. Sometimes it will just engage for no reason and it causes a vibration but after driving it will eventually disengage. I am not familiar with AWD but it seems whatever controls the wheel to engage and disengage is bad, sometimes it seems that it's partially engaged....any ideas? Thanks

 

[Town]

The AWD system has an electronically controlled clutch in the transfer case differential. The transfer case drives the rear axle directly, and drives the front axle according to the electronic setting for the transfer case differential clutch. The normal setting for the clutch is a low duty cycle that allows the front axle to be driven all the time but allow for different wheel speeds to negotiate turns. The electronic control can increase the duty cycle when wheel slippage is detected.

Your front axle is always driven so it appears that your transfer case clutch is sticking or the control module is applying a higher duty cycle than intended. On a straight road this does not matter, but in turns the transmission will wind up and skid a tire on dry asphalt. Is this what you are experiencing?

A number of people have complained about the same kind of symptoms. I have not seen any solutions documented, except for removing a wire to disengage the electronic clutch control.

Good luck.

 

[Jim1761]

Where is the electronic clutch control located?

 

[Town]

Where is the electronic clutch control located?

The Ford diagnostics do not list the 4wd control module as a possible cause for drive train windup, which is what you seem to have.

The transfer case differential clutch is controlled by the 4wd control module. It is located behind the passenger glove box. Lower the glove box door to allow access behind it, and you will see a rectangular box (end view) held by 2 screws with two electrical connections entering from the bottom.

Ford diagnostics for drive line windup relate exclusely to wheel and tire issues although differential ratios are a possible cause. Have you checked wheel and tire sizes and tire wear. All must be exactly the same or within 2/32" in radius. The AWD is not forgiving of differences in the diameter of the tires.

Good luck.