Elli everyone, this is my first post here I hope to get some help. I just bought a 2004 ford f-150 FX4 and at random I will hear a grinding noise. I don't know from where but when I put it in 4WD it goes away and won't come back for a few days. Nothing triggers this either it is completely random, any ideas?

 

The people on here are usually really good at helping people locate ,fix, or find problems but, your going to have to be a lot more detailed in your description of this problem.
Is it coming from the front, the rear, the motor, the trans, the brake area, give as much details about it as you can. I am taking a total shot in the dark here but, if it sounds like it is apart of the 4x4 system, you might check your differential fluid level, or to see if has a burnt smell to it, my f150 4x4 stopped engaging into 4wheel hi or low, the post & people on here helped me figure it out. In the fords the 4x4 motor on the trans, will sometimes stop working. The cure was I put it in reverse, forward, in and out of 4x4 to 4x2 going back & forth 50 to 60 feet and after 5-6 times it jumped right in to prefect working condition suddenly from not even getting a signal at the dash switch. I hadn't used it for 6 months or so. I hit it with some lube and I've put it in 4x4 about once a month just to work the servo motor and keep it greased. Yours might not be fully disengaging
But if the sound goes away when your in 4x4 it might be low, or burnt rear end diff fluid. So when you use the front wheels it is taking some of the pressure off the rear end causing the noise to drop off. Then after being in 4x2 a while with low fluid the grind comes back because the lack of fluid won't let the gear fully engage??? That is a total shot in the dark, with no real details on the issue. And then again you might have a sticking brake caliper, I've had that. The calipers will seize on a ford, common issue from the plastic that the caliper is made of, it cracks from years of heat cycles.

 

More than likely you've got a leak in the vacuum system that operates your 4x4 system. The vacuum actually keeps the front hubs (IWEs) from engaging, so when you lose vacuum they try to engage. That is the buzzing noise you're hearing. Do a search on IWE diagnosis and repair on this forum, alot of good advice on these threads. IWE stands for integrated wheel end if you were wondering.

 

My truck was doing something similar and mine was the IWE solenoid on the firewall behind the battery. I bought a new one for $25 and 20 minutes later my truck was fixed. So as stated above look into the IWE system.

 

I am sorry I was not detailed enough. It is really hard to find out where. Sometimes it sounds like it is coming from the front and I thought it might be my brakes sticking because there have been a couple of times where I hit my brakes and it started actually. I was leaning towards the vacuum as well. I will first check that system out and bye that solenoid.

 

Have someone make slow circles in a parking lot passing you and you may discover it to be the front end, IWE, 4 wheel drive related. As previous posters have stated. Common issue in this generation of Ford. This is how I diagnosed a similar noise coming from mine.

 

Ok thank you everyone and I will check that out and get back to you!

 

Buy !!

 

^ Indeed.

Here are some things to review for trouble shooting and repairs. All pretty easy once you know what you're looking for.

http://www.ford-trucks.com/forums/83...then-some.html


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

http://www.f150online.com/forums/2004-2008-f-150/360269-iwes-removal-replacing.html

 

So I found out the problem! It is the wheel hub assembly I need to replace both sides and these things are cheap and seems like I can only get them at a dealer.