I accidentally forgot to shut off my auto 4wd one morning and at about 80 I got bad vibration when in auto 4wd and regular 4wd. Now I get it all the time when in 4wd mode. On top of that it takes putting the truck into neutral to get back into 2wd once I get the vibration and humming but it all goes away in 2wd. I heard some sort of noise over the radio just before all this happened. I thought in auto 4wd the front axles were disengaged anyways until there was slippage. The service 4wd light is not on and it does kick in and out but I will not use it now that I have this noise. Seeing how we have over 8 inches of snow here today, does anyone have any experience with this problem?

 

THIS perhaps, just in reverse...? Maybe your front axle isn't fully engaging.

 

Don't know about reverse, always going in drive gown the road even in wet snowy conditions.

 

By saying reverse, I meant that you are getting the noise/vibration while in 4HI/4LO/Auto4wd and not in 2HI like the article states. The article talks about the front axle not fully disengaging, but symptoms like you describe could occur if the front axle were not fully engaging when in 4HI/4LO/Auto4wd.

 

IM not sure, that could be. How would I test that?