Screeching noise 2010 F-150 STX 4.6L V8 4x4

[92saturnsl2]

Co-worker brought his truck to me to help him with an intermittent squeeling/screeching noise. A friend of his replaced accessory belt components, the usual suspects-- all idlers, tensioner assembly, belt and yet the noise persists. Said friend condemned the power steering pump, but can't replace it himself.

So co-worker brings the truck to me with a new power steering pump, wants me to replace it. He's able to leave the truck for a few days for the repair. I'm not a fan of the parts cannon approach, so I take it for a test drive and it's absolutely not the power steering pump. In fact everything in the accessory drive is silent, zero play in anything, except perhaps the cheap tensioner pulley the friend replaced which has more play than the factory one probably did, but I'm certain it's not making noise.

I put about 30 miles on the test drive and was able to create the noise twice, lasted about 2-3 seconds each time. I could feel/hear it down toward the front, almost underneath me as if it were drivetrain related.

I put the truck on the lift nothing jumps out at me. Everything is in pretty good condition for a 15 year old truck, but one thing has me wondering. When I rotate either of the front tires, it turns the driveshaft but not the other wheel. I'm not used to seeing this. This should be an open differential (it's a base model) that should turn the other wheel in the opposite direction when I rotate either wheel. I can see it barely try to turn the other wheel (in opposite direction), but then all force I apply gets transmitted to the turning the front driveshaft (which with the truck in 2-high just spins). Does this seem right?

I'm going to button it back up and drive it to work tomorrow (about 70 miles round trip). Hopefully the noise pops up again so I can get more clues.

 

[meep]

Idk about that year, but some fords run a vacuum-based engagement hub - when vac is present the front axles should disengage and not spin the shafts.

 

[TCL]

Starter bendix gear rubbing flywheel from not fully disengaging?
Try bumping the starter ( turning key) while running and see if the sound is the same.

 

[BISCUT]

Idk about that year, but some fords run a vacuum-based engagement hub - when vac is present the front axles should disengage and not spin the shafts.

WHen the power steering issue was ruled out IWE was my first thought. Common issue in many years of F150.

 

[92saturnsl2]

WHen the power steering issue was ruled out IWE was my first thought. Common issue in many years of F150.

You guys are onto something. I drove it to work today and was able to recreate the sound, it seems to happen under load (lower RPM) going up a hill. If I placed it into 4-HI, the noise disappeared immediately and I was able to recreate that several times.

I've read there's a check valve and solenoid that are common culprits. I'll throw a hand vacuum pump on the lines before replacing any parts to rule out a leak first.

 

[BISCUT]

You guys are onto something. I drove it to work today and was able to recreate the sound, it seems to happen under load (lower RPM) going up a hill. If I placed it into 4-HI, the noise disappeared immediately and I was able to recreate that several times.

I've read there's a check valve and solenoid that are common culprits. I'll throw a hand vacuum pump on the lines before replacing any parts to rule out a leak first.

Haven't had em go in my 04 or 15 F150's but have read a lot on them. If your troubleshooting determines that this is the issue, I would start with the solenoid.

 

[92saturnsl2]

99% sure this thing is fixed while saving a co-worker $120 on a power steering pump plus labor, hopefully he can return the PS pump without getting hosed. 15 mile test drive replicating the same conditions and no noise.

It was the 4WD system all along and the culprit was a $10 check valve. Pulled the check valve off, easy test-- it should not pass air in one direction, but it was leaking a decent bit which explains why the symptom was so intermittent and only present under load (where there's not a lot of vacuum).

It uses Ford's hard plastic vacuum hoses and despite being as careful as I could, one broke off right at the 90 degree rubber elbow. Fortunately I had some vacuum harnesses from a '85 F-250 I used to own that had the exact same hoses and rubber elbows. Cut a 90 degree connector from the donor harness leaving 3/4" of plastic "hose" and connected the two with a rubber vacuum hose that provided a tight interference fit. I'm surprised Ford is still using hard plastic for vacuum hoses 35 years later, but even more surprised that the 35 year old harness, I can twist it in circles without breaking, compared to the new stuff that snaps if you look at it wrong.

 

[meep]

I had one of those check valves in my Amazon shopping cart, as a previously f150 owner. I am glad they use locking hubs, and it’s a cheap part.

 

[92saturnsl2]

I had one of those check valves in my Amazon shopping cart, as a previously f150 owner. I am glad they use locking hubs, and it’s a cheap part.

They seem to have it backwards though, most non-Fords I'm familiar with operate by supplying vacuum to engage the hubs.

The downside to that approach is if something goes wrong, you don't know it until you need 4WD and it doesn't work.

Some engineer at Ford probably had a bright idea in that when the vacuum system fails, the hubs are locked which just reduces gas mileage by spinning a driveshaft via the front wheels which doesn't do anything until you select 4WD.

I don't think they fully thought out what would happen with partial vacuum, which leaves the hubs in a partially engaged state, which would eat up the hub actuator if left that way.

 

[meep]

They seem to have it backwards though, most non-Fords I'm familiar with operate by supplying vacuum to engage the hubs.

The downside to that approach is if something goes wrong, you don't know it until you need 4WD and it doesn't work.

Some engineer at Ford probably had a bright idea in that when the vacuum system fails, the hubs are locked which just reduces gas mileage by spinning a driveshaft via the front wheels which doesn't do anything until you select 4WD.

I don't think they fully thought out what would happen with partial vacuum, which leaves the hubs in a partially engaged state, which would eat up the hub actuator if left that way.

Indeed. I’ve thought about it too. Partial vacuum could harm the hubs. And I’ve read that the locking ring has some plastic parts that don’t handle abuse well. But full loss of vacuum would lock the hubs and allow 4x4 to still be acceptable at the transfer case. This is a much better place to be that day you need to use the feature, if you weren’t aware of the vacuum problem. They say to go in on 2 and out on 4. I’d hate to go in on 2 and … sit there stuck because of a $9 part.

Hey - nice troubleshooting

 

[92saturnsl2]

Indeed. I’ve thought about it too. Partial vacuum could harm the hubs. And I’ve read that the locking ring has some plastic parts that don’t handle abuse well. But full loss of vacuum would lock the hubs and allow 4x4 to still be acceptable at the transfer case. This is a much better place to be that day you need to use the feature, if you weren’t aware of the vacuum problem. They say to go in on 2 and out on 4. I’d hate to go in on 2 and … sit there stuck because of a $9 part.

Hey - nice troubleshooting

Thanks, it does make sense. I've had a surprise experience where 4WD didn't work because of vacuum lines, a 2000 Kia Sportage. Didn't leave me stranded but very close. That model had manual Warn hubs available (inexpensive) that I wasted no time installing.

I have to give Ford some credit, I believe Dodge/RAM (perhaps Chevy/GM also) had the hubs locked in at all times, at least in certain years.

 

[meep]

Thanks, it does make sense. I've had a surprise experience where 4WD didn't work because of vacuum lines, a 2000 Kia Sportage. Didn't leave me stranded but very close. That model had manual Warn hubs available (inexpensive) that I wasted no time installing.

I have to give Ford some credit, I believe Dodge/RAM (perhaps Chevy/GM also) had the hubs locked in at all times, at least in certain years.

I LOVED warn manual hubs. Saved my 2 mpg in a 97 pathfinder and never let me down.