tkstock

My 2008 F150 4WD is making a noise when I accelerate. It makes the noise primarily at higher RPM's - I haven't narrowed a particular range yet. I've had two mechanics look at it - the Ford dealer and another recommended mechanic. Both said it was the IWE system - the Ford Dealer said it was both front IWE actuators - the other mechanic said it was the IWE solenoid.

What they didn't know is that I had the passenger-side IWE actuator replaced and that I know that system quite well - and was pretty certain it wasn't the problem. Just to make sure, I verified that the vacuum being drawn on the system is 15"Hg, and both actuators are disengaging properly at well under 5"Hg.

That's all well and good that I proved that system to be working properly, but I have no idea what the noise is. It sounds like a bearing of some sort - but the second mechanic said they checked the wheel bearings and they "felt solid".

Would the front differential have bearings that might be a problem under acceleration? Any thoughts on this one?

I was able to record the noise today - best I could do...

Bossgame

Well if your vacuum lines, solenoid, check valves, reservoir box, and actuators are working correctly, then when the engine is on, the front hubs are disengaged from the front axles. That being said, and all that working properly, your front diff is never in action, making a bad bearing in your front diff not part of the problem.

Now if you haven't replaced the solenoid yet, I would start there. Also, if you had to replace one actuator, there is a good chance that the other one is failing also, and is a good idea to replace both.

My opinion is that you're losing vacuum to your hubs causing them to try to engage under load. I had the same issue and a new solenoid fixed it, although some guys aren't that lucky. When you accelerate, you lose vacuum in the intake, and that's where your check valves, reservoir box, and solenoid come into play, and should lock in the highest vacuum applied to them.

I would thoroughly check all of the vacuum lines, as small cracks in those can cause this issue also, and then start narrowing it down. Replace the solenoid as I said. $35. Then go to check valves, and do all the rest until you find it.

Good luck.
Kody

tkstock

I appreciate the response. Even under load, the vacuum lines are pulling over 13" Hg. The hubs are disengaging at well under 5"Hg (my meter starts at 5). I really don't feel it's that system - I'm looking for other possibilities. I know what it sounds like when the hubs are trying to engage - again, I had that exact problem earlier this year. This isn't that problem. It sounds significantly different.

BTW, I did replace the solenoid - no joy.

I'm looking for other possibilities.

Bossgame

Ya I feel ya. Hope someone can jump in and help you out man. I hate noises that aren't supposed to be there hah

lewissa81

I've also heard a few stories of heat sheilds coming loose and making a somewhat similar noise.

papa tiger

I would unbolt the drive shaft.

tkstock

That's a thought. I did notice the flexible heat shield was pretty close to my drive shaft - I bent that back and that didn't help. It was a thought. I'll check the others, though.

tkstock

You mean remove the front drive shaft completely? Are there any issues to consider when doing that? I assume I could drive the truck without it without consequence?

papa tiger

Once it is out of there the noise either is a wheel or the transfer case itself. Does yours have an Off Road Mode Switch?

tkstock

I'm not familiar with that switch - so I would guess no. Just the standard 2WD/4H/4L.

Question - when everything is working perfectly, does the front drive shaft turn at all? Does the transfer case even do anything in 2WD?