Thanks Mariel. Had one out of town dealer (Vaughan) look at it so far (out of town for work for a week) so when I drive home I'll be listening for the noise and what I can do to recreate it in hopes to show to my local dealer (Welland) and see if they can diagnose it. That being said, I was quite pleased with the service I received both at the dealer, as well as the helpful nature of all the kind folks here! Will be certain to keep everyone updated, if they wish. Cheers!

 

I see this was many years ago but I’m hoping you see this and I can ask you if you ever figured out what exactly was wrong. Having same issue with truck- 2020 f150.

 

if I remember correctly, it was the IWE (integrated wheel end) assembly acting up secondary to vacuum pump issues… although this was many years ago, like you said, so memory may be a little off. It was fixed under warranty, thankfully! I believe I recall it not being an uncommon issue for that generation of truck… good luck!

 

I see there is actually a recent question on this board. I too came here with a similar problem w/ 2011 4X4. I thought I would add some extra for you. You may have already solved your problem. I don't know how extensive mine will be. I would be curious to hear back how extensive yours was, where it stopped to resolve, and ballpark cost. I can't get started with a DIY until I get my hands on a decent impact wrench.

Problem: in 4X2 loud screech; usually accelerating, slow speeds, or even under stress uphill; let off gas and screech stops; It may or may not happen again for a month. You are not crazy. You did hear it. It will gradually become more frequent. The 4WD actuator is trying to engage itself but only partially. After all, you are in 4X2. It engages and backs off, engages and backs off...wash, rinse, repeat sometimes. My problem may have gone one step further. I would swear last night mine went into 4Low by itself on the way to the grocery store. I was going slow (1,000-1,500 RPM under 30 MPH) off of a red light. I was in 4X2 when I got the screech. Switched to 4H just after the light. I may have moved switch too far but it is not supposed to be possible. I believe we can only go into 4L in N less than 5 MPH with foot on brake. I got an awful screech with a check 4X4 wrench light. Then the "shift to neutral before going to 4L". Stopped quickly. Hazards on. Shifted to 4H. Parked at store and tested from stop. All was well. Shut off engine in what I thought was 4X2. Left parking space. Sluggish. It was in 4L but I didn't know it. Screech again with 4L shift warning wrench. Stopped in lot. Put it in 4X2. Put it in 4X4. All was well 10 blocks home. Don't let yours get this far.

This could be a very cheap and easy fix. $15-$50 initially. You barely need a small screw driver. For the potential, more involved problem, I tried to get a ballpark quote from Rountree Ford in Shreveport. Mums the word other than $179 diagnosis charge. IDK why it is like pulling teeth to get a rough estimate. If it is $5,000, I must DIY or sell. If it's $500 I might not bother and let you do it. I only wanted a typical price for the job plus or minus $200 to $500.

So, there are some rubber and plastic vacuum tubes under the hood and likely near the windshield, driver's side, brake master cylinder. See video link. There is also a plastic solenoid (yours may have a plastic cover on it to keep water out), an electrical connector, and a blue and white plastic check valve. It is all plug and play. The solenoid clips on. These hoses supply vacuum that keeps the 4X4 from engaging. When you flip the 4X4 switch, it removes the vacuum and engages your 4WD. For $15, you can replace that check valve to see if the problem quits. I replaced all hoses except the one running to the wheel, solenoid, and check valve. Hoses all came together in one part package. Some of these hose connections are on pretty tight. Be careful unplugging them. I snapped off the plastic hose fitting on another solenoid that's connected to the brake master cylinder, and it cost me another $40 and 5 days waiting for the part. These can be pressure tested to isolate which one may be the problem. For the price, I just ordered the whole hose assembly that included the check valve and replaced all of it including the solenoid sold separately. That's the start. Anyone can do it. Unplug and snap. Mine didn't solve the problem. Link shows what it looks like and how to do it.

Next step: See video link. The IWE "hub" or "actuator". It is the part the vacuum hoses operate. $80 part. Man in video above thinks it is an $800 job. Very involved job. Med heavy difficulty. I believe I can DIY this myself. As I stated, I couldn't get even a ballpark quote. I believe mine is faulty. I don't have a pressure testing tool to know if a vacuum leak elsewhere is causing my problem. This isn't something that can wait. We can drive short distances and lower speeds. Putting the vehicle into 4X4 high will keep the grinding from happening as the IWE is fully engaged intentionally. Driving in 4X2 is okay only when it is okay. Grinding is never good even when it is intermittent. Now the only way to prevent this is to drive in 4X4 H. Unless we are full of money bags, we must protect the wheel hub gearing and the CV axle gearing and the front diff. There are links above showing how the job is done. Makuloco is awesome. I have another video link where a fella goes through the whole gamut including pressure testing the hoses through IWE replacement. I think he said he's working on his own truck. He has an impressive shop and upwards of 150K subscribers. He is a well-spoken, good teacher. Great filming job. Anyone would do well to watch this before a DIY.