I'm trying to figure out what happened the other day. I had the IWEs on my 2012 F-150 replaced a couple of weeks ago and that cured the low groaning sound from the front at very low speeds. A couple of days ago I took it on the freeway for a 50 mile trip and not sure at what point I noticed - maybe halfway - but there was a low hum, like the 4X4 was engaged. The the **** was on 2 wheel and none of the 4X4 indicator lights were on. The road was grooved and so I assumed that's what it was. However, when I got off the freeway the noise was still audible over about 40 mph. I checked to see if there were any detectable vacuum leaks but could not find any. In neutral, I switched the **** to each 4X4 mode, giving it a few seconds to respond, then would move the truck backward about 10 feet and run through the modes again and then forward 10 feet and through the modes again. On the way home that bought me about 25 miles until the hum returned. At that point, pulling off the freeway and trick of running through the modes didn't work. Thinking about how the 4 automatic worked, I switched to that - while driving -and the hum went away.

Secondary to that, when running through the different 4X4 modes, in 4 Low the check 4X4 light came on and there was a loud click going into 4 Low or from 4 Low to 4 High, The was no click going from 4 Auto to 4 High and back. This morning I took it to Autozone to see if any codes would show up - they did not. I drove around going through the different 4X4 modes and interestingly the check 4X4 light never came on. Most of the time, but not always I heard the click going into 4 Low and back. I took it on the freeway, no hum.

I'm still going to take it back to the dealer - who did the IWEs - and see if that installation could be related to what's going on. Have any of you had similar experiences and how did you fix the problems?

Thank you!

 

when you turn the **** on the dash to 4 x 4 it engages the transfer case and the front drive shaft turns... that is the clunk.

When truck is parked and no vacuum, the front IWE are engaged.. Start the truck and vacuum pulls them out to get to 2 x 4... If you have the IWE engaging without moving the ****, then you have a vacuum leak and the IWE are engaging on their own... This has nothing to do with the transfer case or drive shaft... they are not engaged during a vacuum leak.

 

Thanks, it does seem like it has to be a vacuum problem because I don't think it's possible for the differential to engage without the electronic signal from the **** - unless there's a short. You used the word clunk - and I've heard others also - to describe the sound of the differential engaging. I would call this a pretty sharp and loud click - does that fit within your word "clunk"?. I used to have an 87 F-150 that had a pretty dull sounding "clunk" when engaging. This is different.

Thanks for your insight

 

Before i signed in everywhere the posts have "****" it was changed to "****".

 

When your axleshafts are engaged from IWE's the "differential" has no choice but to spin, thus the pinion has no choice but to spin thus the front d/s has no choice but to spin. "The leg bone's connected to the hip bone" and so on

If in the cab your click is relay(s). If outside the cab your click is almost surely the shift motor on t-case

I'd pull the vac lines at each IWE and see if they hold vacuum

 

Thanks for your input. It's going back to the dealer that put the IWEs in tomorrow so they can check their work and see if anything else stands out. Hopefully will find the issue. Since this time, my son put about 100 freeway miles on it with no incident. I personally like things that fix themselves, but not holding my breath!