My 2012 keeps making a noise like the IWE grind coming from the front end. Everything seems to check out though when I do the vacuum test with a pump. Hold pressure just fine before and after the check valve. When it does the noise, i pull over throw it in 4x4 and then back into 2wd and it stops for a while.

One thing that is confusing me is I disconnected the vacuum lines (all of them, before and after the solenoid) and jacked up one tire. It still locks into place and unlocks when I switch it back and forth.

any ideas?