The hubs are engaged by spring pressure, and a diapragm under vac pushes against the spring to disengage them. Under heavy load or acceleration, the engine has a weaker vac signal, possibly weak enough for the springs inside the hub to overcome the diapragm and partially engage the hub.

The iwe is usually the culprit, but the tech tested it and says its ok. Next step is to check how much vac the engine is suppling, if you have bad rings, the vac will be weak, even weaker under load. If the engine vac is strong, the next step is check the vac hose between the IWE and the hub, there is probably a pinhole in the line somewhere. If that checks out, then you probably have a bad diapragm in the hub.

Something is causing the hub to reach the theshhold of engagement, you just have to find out what it is. Since it is only on one side, I'm leaning towards the vac hose or the hub itself.

 

There are 2 IWE's (Integrated Wheel End or for a simpler term, hub) and 1 IWE solenoid, which sends vacuum to the IWE's to disengage them. Default position is engaged. If the solenoid was bad, more than likely, both IWE's would be making noise.

 

You're probably right... i just hope the dealer's tech knows as much about it as you do. Thanks for your help.

 

Correct, but if one hub has a stronger spring than the other, then only that side will grind, as long as the vac signal is between the engagement threshhold of the two hubs. If it drops below both, then both sides will grind. And you know, as well as I do, what are the odds that both hubs will engage at exactly the same point. The may be close, but exact?

On my old 05, that is exactly what happened when the IWE solenoid went out. The right hub was grinding while the left was silent. They replaced the solenoid and all was fine.

 

Well the dealership just called me and said they went ahead and replaced the solenoid and still had the noise so they kept looking and they found "broken" vacuum line going to the right side. Hopefully this takes care of it... $287 bucks later for a $34 part and hose... What a deal...lol!

 

my wifes explorer is doing the same thing. Has been for a year. Never found the problem.

 

That's what I was thinking. Maybe a seal leaking vacuum on the right IWE and trying to lock in. Might try putting in 4x4 and see if the noise goes away. I haven't had this problem yet (knock on wood) but have read many folks who have had this happen. I still don't understand why they designed it this way.

 

It is your inner wheel hub, runs about $96 dollars a the dealer. Had the same issues you had and I replace my IWE Solenoid and it still did it. I replaced inner hubs one a a time and it turned out to be the inner hub. Email me and I will give you my number and I can explain it a lot better.