'97 Explorer 4x4 problem, ate front diff.

This spring my wife was driveing our Explorer and when she got home she told me that the 4x4 lite blinked twice and it was steering hard. When I checked it, it was locked in 4x4 without dash indication and I had brass in the front diff. The front diff was eaten, so I installed a used diff and the truck was still stuck in 4x4 hi.

So, trailered it to the dealership and they said that I needed a shift motor and speed sensor for about $1000 total. The tech disconnected the transfer case clutch, the brown wire mod. The truck now drives fine, but I only have 2 wheel drive. I am going to try the clean up on the motor. Is there a way to test the speed sensor? Should a bad speed sensor generate a code?

I have the command track that is supposed to have 3% power to the front at all times. The tech told me that the truck will shift the motor into 4x4 when it is needed, so how does the unit supply any power to the front if it is in 2x4 until I have rear tire slip?

What do you guys thinK?

BTW, the truck was in the auto 4x4 switch setting when this happened.

Matt

The speed sensor detects slip at rear then the computer commands a pulse width modulated solenoid to engage the front axle as per rear slip.The more slip at rear, the more engine power is directed to the front diff. And visea versa. There should be a code for either a front or rear speed sensor. You can Ohm them but that isnt much of a test. You need to see the frequency of the AC(like with a fluke 88) Maybe don't worry about the motor for now(unless its stuck in 4WD HI or LOW) Figure out what sensor is defective. It seems the switch would have to be in 4HI to destroy the front diff, hmmm...