I HAVE AND EXPENDITION 425 AND WHEN IN IN MUDD SOME TIME IT WILL NOT COME ON BUT SOME TIMES IT WILL AND WILL NOT GO OFF THE 4WD BUTTON IS OFF.

 

this happened to me once when i was pullin a big trailer in the snow....what i had to do was come to a complete stop and switch it on and off...remember never engage your 4wd when any tires are spinning

 

What, why never engage while spinning?

Its just a magnetic engagement up front I thought...

I've never heard this before?
Tell me more about why you shouldn't engage while running..

 

I believe what he was saying, is not to engage the AWD when the rear wheels have lost traction, and are spinning. The front wheels would immediately engage, and would/could tear up some expensive parts.
Brian

 

You can switch to 4wd on the fly but if your stuck your not to hit the 4wd putton while the back wheels are spinning I'm not sure why but it's in the manual.

 

I am moving when I engage 4wd 90% of the time. But I am not applying the throttle. I let off, swtich, and keep going. Sometimes if it is revved up real high it won't engage until I get the RPM's low, and then move again. I thin it's a saftey feature so you don't engage at high RPM and mess up a drive shaft, u-joint, or cv joint.

 

There is a safety built in for just that reason. If your engine RPM's are above 4,000-RPM's and you engage the AWD switch the front hubs will not energize. This is to prevent a rider engaging the AWD system while the rear wheels may be spinning.

I thought I had a problem also until I looked in my service manual and read up on the LR-83 module.