04 EX 4.6 AWD 40-70 MPH Vibration - Viscous Coupling?

[Nogaroa4]

Alright, so I have/had a Vibration in my pedal (DBW) between 40 and 70, most noticable between 60 and 70. The car also seemed to not like to accelerate if stopped and trying to make a turn. (In and out of my driveway since I have a flagship driveway.

So I did some reading, and some more and found that it could a couple different factors, one of them being my Viscous Coupling in my transfer case. So I jacked the back of the EX up and put 2X4s in front of the front wheels. I could barely get the back wheels to spin without having the front wheels starting to climb up the 2X4s. So I'm thinking that since I have 129k on the explorer that my Viscous Coupling in the Transfer case is starting to seize up.

Therefore when I drive, it basically like driving in 4WD High all the time. Since from what I understand, even though i have AWD, the front wheels only engage when the back wheels don't get traction or slip.

Is my theory right? or am I missing something.

FWIW the difference in tread between my front wheels and back wheels are 3/32 inch.

 

[05explorer1974]

Yes you are correct on the awd/4x4 about engagement when the rear wheels slip. That could part of your problem. A couple of things possible. They had problems with the drive shaft and changed them because of it. Also Your hubs could have a vacuum leak whch has the locked or engaged them. They will not release because of the air leak common problem. That coupler was more common on the 97-2001 Explorer's and Ranger's then the newer ones. If your tires are worn different it will cause a ton of problems. I rotate mine every oil change because of this. What happens is because either the fronts or the backs are not within the range of each other the computer senses one set is spinning faster then the other so the systems thinks it is slipping when it's really not. On these Explorer's you are best to replace all 4 at once and if their is that big of a difference you will have to replace them. Your problem can be caused by the tires being to far apart or out of Ford's range in tread depth.