I am getting so frustrated with my 06 4x4 lariat lately. I am no mechanic but I know my truck fairly well and do most of the work needed myself. A while back I noticed a weird noise coming from the drivers side front wheel when I made a hard turn to the right. It was really noticeable when coming off of a clover leaf type overpass with a hard turn for an extended period of time. With the window rolled down it was quite loud. To help diagnose the problem, I put the truck in 4HI and took the same turn and the noise was gone. I figured it was either the hub assemble or the half shaft. there is no noise at all when driving straight or turning to the right, only when turning hard to the left.
First thing I thought I would try is the hub assembly. I put a new hub assembly on it and just as I was torquing the spline nut at 20ft/lbs (me using my torque wrench for the first time and not knowing the sounds it makes when reaching the desired torque) i ended up over torquing it and snapping off the end of the shaft!!! Sounds funny now but not so much then : ) so I had to take it all apart again, remove the entire half shaft and replace that too. So now that I have replaced both items that I figured were potential causes of the noise, I put everything back together and drove it. The noise was gone.
Two weeks later, the noise is back but not quite as loud as it was before and of course on the same side and the same scenario. So I figured that maybe because the hub assembly was over torqued once (when the shaft snapped off) maybe that damaged something inside the hub that caused premature failure. So I got the hub replaced under warranty (thank god) and replaced it with the new one and torqued it properly at 20ft/lbs.
The noise was faintly still there!!!!!
Put it in 4HI on the same turn and noise completely gone! I am lost now.
New hub assembly, new half shaft and the noise is still there. The only other thing I can think of is the IWE assembly that engages the hub during 4x4 mode or there is a slight vacuum leak that is disengaging 4x4 like its supposed but during a hard turn only the vacuum isnt strong enough to hold the IWE from trying to engage and causing the strange noise.

Please help!

The 4x4 seems to engage and disengage properly as I can hear it when stopped. I can hear it click when engaged and click when disengaged. I have replaced the relays behind the battery about a year ago.

 

It could be that the IWE isn't dis-engaging all the way due to mechanical problems within the IWE, or, as you say, a vacuum leak. Carefully inspect the line and the check valves on that side. Use a vacuum pump to check the IWE for dis-engagement travel. Also go here: https://www.f150online.com/forums/ar...then-some.html

 

Thanks Sam. I will have get myself a vacuum pump and keep you posted. I just seems odd that I would only experience this under hard turning conditions. My only possible explanation is that the momentum during the hard turn is shifting the IWE closer to engaging because I certainly haven't noticed anything wrong driving straight or turning the opposite way.

Thanks for the advice.

 

I figured I would update everyone what my diagnosis was for future readers. After purchasing a vacuum pump, I tested the IWE hub actuator to see if it would hold vacuum by unplugging the hose right on the IWE and plugging in the vacuum pump. I applied 20lbs of vacuum and it would slowly lose vacuum. I tested a friends f-150 to see if thats normal and his would hold 20lbs of vacuum so clearly mine was disengaging but not all the way due to the vacuum loss. This caused it to partially engage during certain driving conditions and make the strange noise.

 

Glad you got that one figured out...everything is a learning experience...