tkstock

I have a 2008 F150 5.4 4WD w/Super Crew.

I've owned the truck just over a month. I've been told that it's a good idea to engage the 4WD every now and then (on wet pavement).

I did this a couple of days ago for the first time. When I switched back to 2WD, there was a new sound - almost a road-noise like sound - that I could hear, and there seemed to be a bit more drag on the truck and a slight vibration in the accelerator pedal. When I would switch back to 4WD, the sound would go away. I would liken the sound to having mud tires on the truck. The 4WD light on the dash switches as expected.

The sound does not always reappear when I switch back to 2WD. In fact, I can get the sound to go away much of the time by switching briefly to 4WD and back, and it will be quiet for a while - usually until I come to a stop. Then the sound sometimes returns. It is not consistent.

I can tell when the 4WD is fully engaged - turning causes a lurch. When in 2WD and making the noise, the truck does not lurch, so it's not physically stuck in 4WD, but something feels like it's partially engaged.

Note: I'm only switching to 4WD briefly at times to get rid of the noise, I'm not running it that way all the time. This has only been happening for a couple of days, so I haven't figured out an exact pattern to the behavior.

I took it to a mechanic yesterday to make sure I wasn't messing things up by continuing to drive it and they came back and said they THOUGHT it was a bearing around the front differential and suggested a $1000 rebuild. I got the impression they were guessing though, and when I told them it didn't do it all the time, they indicated they would go back and read some more on it.

Anyone experience something like this?

techrep

iTrader: (1)

Replace your $60 IWE solenoid located on the firewall behind your battery...no $1000 mechanic needed

60DRB

IF the solenoid is the issue;

http://www.tascaparts.com/parts/2006...?siteid=213668

Read some here;


http://www.ford-trucks.com/forums/1211749-4wd-not-working-help-me-pinpoint-my-issue-plz.html#post12662529

https://www.f150forum.com/f72/how-diagnose-your-4x4-system-esof-186872/

http://www.ford-trucks.com/forums/836438-everything-you-wanted-to-know-about-the-iwe-system-and-then-some.html

tkstock

If there were not functioning properly, would it ever get out of 4Hi? Do those "partially" fail? The mechanic said the vacuum being pulled on the part at the hub was fine (the vacuum is controlled by the solenoid, right?) Just curious if it could work some of the time and not at other times.

BTW, thanks for the quick response!

tkstock

Great post. Thanks for the info.

homer

You should vacuum test the hubs manually anyways... I could run my truck and it was enough to slightly disengage one... When I put my hand vacuum tester on mine, I'd pump it up and it would hold but slowly drain on my passenger side, but my drivers side would held for like 5 minutes. Running the truck and turning the hubs can be a bit deceiving depending how bad they're leaking.

What happened with me back in 2008 was my drivers side was making significant amounts of noise. I was new to the IWE system at the time so I replaced it and the noise was gone. I was on the highway a fair bit and when I'd hit hills, the drivers side would start to grind again (under load - climbing - low vacuum situation). Anyways, it didn't take long to drive me nuts so I bought a hand vacuum tester, tested both sides and found my passenger side was completely shot. Since it was stuck engaged and leaking, climbing a hill, losing vacuum, the drivers side would partially start to engage. I wrote a post years ago about this however the articles TKStock provided you are much more detailed and cover much more.

techrep

iTrader: (1)

Depends when your selecting 4H...truck makes more vacuum at Idle than at speed..and if your solenoid is leaking... it makes it worse... it could be a few other things like your drivers side check valve or your lines going to the IWE itself...but swapping the solenoid is the easiest/cheapest ...can always go buy a vacuum pump and troubleshoot...but I would not give somebody $1000 to rebuild hubs...

tkstock

Does anyone know if there is a way to temporarily bypass the solenoid? If I were to draw a constant vacuum on the IWE actuators, would that keep the 4WD disengaged until I get the new solenoid?

60DRB

If you read what I posted before... They tell you how to "bypass" the solenoid. Just disconnect the vacuum line from your intake manifold and plug the line ends. The IWEs will be engaged all the time then. I did that while I waited on my parts. I didn't notice any real difference in mileage, etc.

techrep

iTrader: (1)

He said he wanted them to be dis-engaged...and no if you plug the lines they will be engaged.