I have an 06 f150 and at first my 4x4 was working fine..the other day I used it to pull a doge out. But in both 4x4 high and low it would pull and then 4x4 would go in and out while it wasn't pulling it made a grinding noise..then I went to pull a Chevy out yesterday and when I turned the switch neither of the lights would come on..I thought it was the switch maybe..and tonight on my way home it was making a whining noise sounded like it was coming from the front drivers side tire..then I swerved from left to right to see if it was stuck in 4x4 high and then noise went to the other side and quit...then I went down a dirt road and it was I'm 2 wheel..so basically what I'm askin is...why won't my lights come on when switched to 4x4??? What would cause It to jump in and out of 4x4?? And what do y'all think the whining noise was..all replies are greatly appreciated..thanks in advance

 

A vacuum leak .... bad solenoid....T-case motor or IWE...got to troubleshoot with a vacuum pump.

 

Doge stuck. Such mud. Wow. Plz halp