My truck has never made any noises like this in the front end in the 30000 km I've owned it. This winter has been very mild up until yesterday when we had a sudden plunge in temperature. (-25C) I started hearing a grinding noise in the front end that would go away if I engaged 4x4 and it would stay away for quite some time after disengaging 4x4 as well. Since I'm driving nearly 200km to school on sunday nights and heading back home on friday nights I just disconnected the vacuum lines from the solenoid on the drivers side to keep the iwe's engaged. So now the grinding noise went away (will be testing vacuum when it warms up again and I have time to do so). Also planning on replacing the check valves and the solenoid as it is the old style that has no drip hood on it.

So now with no vacuum being applied to the iwe's my front end is engaged all the time, less fuel economy for now but whatever. My real issue here now is with the vacuum lines plugged off I continue to get a clunk sound (very similar to the sound it makes when I put the truck in 4HI) on the drivers side very randomly not at highway speeds but only when driving around town. It's really frustrating to be hearing this noise as there should be no reason for the iwe to be engaging and disengaging constantly with no vacuum.

Does anyone have any ideas or explanation why it continues to clunk with no vacuum? Unless this noise is completely unrelated to the 4x4 system, I'm not sure. Any suggestions would be greatly appreciated!
Truck has 120000km

 

Is the clunk sound when you hit a small bump? That happened to me and it turned out to be the stabilizer link. It connects the lower control arm to the sway bar and it costs about 50 bucks. Check the boots on it. I took mine off to check play in the joints before I bought the new part.

 

Yeah sometimes it's when I hit a small bump and sometimes its just driving down a smooth stretch of road (we don't have many of those here in Alberta)

 

I thought you disconnected the vacuum lines to the IWEs to stop the “grinding” sound, and it did stop.

So perhaps the new “clunk” sound is not an IWE issue.

With the IWEs engaged and the transfer case in 2H, the front driveshaft will not be powered by the transfer case, but will be powered by the front wheels through the IWEs/front diff. Have you checked the front DS u-joints and slip joint as well as for chain slop in the transfer case?

 

would chain slop in the t-case not be causing sound all the time?

I haven't had a chance to inspect anything and likely wont be able to for quite some time until it warms up a little bit. My dad (diesel tech at local ford dealer) has his own hoist at work but it's quite difficult to convince him to got in on a Saturday for a quick inspection lol which is unfortunate because you can't beat a hoist for doing stuff quick

With that being said if I get the chance to take the truck into the warm garage at some point some weekend I will add your suggestions to the list of things to check! thanks