Humming noise front end?

[Apexmaster]

Good morning and happy new year to all
I own 02 explorer xlt 4.0 auto. Ever since I got the vehicle it has this humming noise only from 55mph and higher. And only while on the gas. When back off gas it stops. It is a humming noise not grinding. For longest time I thought it was coming from rear, but yesterday I had my wife drive car and I sat in rear. And its not from rear. Its from front for sure. Its not wheel bearings, I check those. Transmission oil good, shift very smooth . I will try make video and post it.

 

[drdoom]

Get @imp in here, he knows a lot about driveline diagnosis.

 

[Apexmaster]

2WD or 4WD?
Any recent maintenance work or part changes?
Stock AirFilter+Housing? Could try installing a fresh AirFilter.
Make sure PCV suction tube from right ValveCover to AirIntake Accordian Tube has not come loose.
Check AirIntake AccordianTube & all VacuumHoses for leaks.
Remove+Clean\Replace PCVValve with CarbThrottleSpray on rear of left ValveCover.
Clean ThrottleBody+Plate with CarbThrottleSpray.
Remove+Clean & new\lubed FigureEightSeal for IACValve; once had whistle from mine >3000rpm until I Cleaned+ReSeated it.
Could also be RadiatorFan\Clutch; how old is this Clutch?
Does noise vary with AC on\off, Heat on\off, OD on\off, 4WD on\off?

Do above items one at time then test drive to isolate cause.

4wd. Nothing changed i hot the suv with the noise happening. It did have stock air box filter but I installed aftermarket k&n . Noise was there from beginning. Engine runs really strong and been lady driven 1 owner suv. I dont hear anything weird coming from engine.

 

[imp]

Get @imp in here, he knows a lot about driveline diagnosis.

But only because every mistake that can be made, I DID, and kept careful mental track avoiding repeats. First, whine or howl under load (55 mph, working to keep vehicle rolling) which disappears upon release of gas pedal and returns upon depressing it, almost always originates in GEARS (somewhere). I've learned it is difficult to predict noise location accurately from within the vehicle. Even underneath, unless stethoscope is used.

I believe all Explorers with 4X4 unless they have mechanically or electrically disconnecting drive hubs in front, have ring and pinion gears always turning. Some had a funky vacuum-operated disconnect which I THINK disconnected axles from driving driveshaft in 2WD mode, note I THINK, not sure how it worked. But for certain, front ring and pinion howl is pretty much ruled out if only present on one gear tooth face (drive or coast face), in 2WD; if it's present in 4X4, it could be front diff., or rear diff. If present only in 2WD (actually 4X4 AUTO), I would pull the rear pumpkin cover off and inspect the gear teeth. Wiped clean, they should be uniformly shiny, no visible scoring or darkening; look also for chipped edges.

Very, very unlikely, but those dubious IFs come up now and then to bite one's ass, play in the driveline, probably rear, U-joints not yet knocking, coupled with wear in pinion bearings, can allow gear tooth misalignment sufficient to cause whine. Misalignment due to ANY cause will cause whine: insufficient diff. carrier bearing preload, or bearing wear.

Disregard the appearance of the pinion below. Intent is to show profile, or shape, of ring gear tooth faces. Note they are sloped gradually in one direction, and very steeply, almost perpendicular, in the other. The first is the "coast" side, which transmits only frictional torque through the driveline to the engine, throttle closed. The steeply-sloped teeth show the "drive" side, which transmits the engine's power to the wheels. Coast angle tends to "spread" teeth apart while drive angle "locks" them together. The gearset shown, incidentally, is for the Ford 9-inch axle. A whole 'nuther story exists for front driving axles, in which the role of the tooth shape is often reversed (with accompanying loss of strength).

story exists for front

 

[Apexmaster]

But only because every mistake that can be made, I DID, and kept careful mental track avoiding repeats. First, whine or howl under load (55 mph, working to keep vehicle rolling) which disappears upon release of gas pedal and returns upon depressing it, almost always originates in GEARS (somewhere). I've learned it is difficult to predict noise location accurately from within the vehicle. Even underneath, unless stethoscope is used.

I believe all Explorers with 4X4 unless they have mechanically or electrically disconnecting drive hubs in front, have ring and pinion gears always turning. Some had a funky vacuum-operated disconnect which I THINK disconnected axles from driving driveshaft in 2WD mode, note I THINK, not sure how it worked. But for certain, front ring and pinion howl is pretty much ruled out if only present on one gear tooth face (drive or coast face), in 2WD; if it's present in 4X4, it could be front diff., or rear diff. If present only in 2WD (actually 4X4 AUTO), I would pull the rear pumpkin cover off and inspect the gear teeth. Wiped clean, they should be uniformly shiny, no visible scoring or darkening; look also for chipped edges.

Very, very unlikely, but those dubious IFs come up now and then to bite one's ass, play in the driveline, probably rear, U-joints not yet knocking, coupled with wear in pinion bearings, can allow gear tooth misalignment sufficient to cause whine. Misalignment due to ANY cause will cause whine: insufficient diff. carrier bearing preload, or bearing wear.

View attachment 326573

Disregard the appearance of the pinion below. Intent is to show profile, or shape, of ring gear tooth faces. Note they are sloped gradually in one direction, and very steeply, almost perpendicular, in the other. The first is the "coast" side, which transmits only frictional torque through the driveline to the engine, throttle closed. The steeply-sloped teeth show the "drive" side, which transmits the engine's power to the wheels. Coast angle tends to "spread" teeth apart while drive angle "locks" them together. The gearset shown, incidentally, is for the Ford 9-inch axle. A whole 'nuther story exists for front driving axles, in which the role of the tooth shape is often reversed (with accompanying loss of strength).

View attachment 326574story exists for front

Yes, I removed front driveshaft drove it with rear only. Still does it. This weekend I'm going to pull out resr drive shaft and drive only front wheel drive

 

[imp]

Yes, I removed front driveshaft drove it with rear only. Still does it. This weekend I'm going to pull out resr drive shaft and drive only front wheel drive

In doing so, the vehicle may not move at all in 4X4 AUTO, and will need to be switched to 4X4 HIGH to activate the front driveline.

 

[Apexmaster]

In doing so, the vehicle may not move at all in 4X4 AUTO, and will need to be switched to 4X4 HIGH to activate the front driveline.

Good point. I thought auto and 4 high are basically same thing. Just 4high is manually turning on not leaving it to computer to detect slip. I was also told could be torque converter related. As stated i will try make video but its really hard to hear it. My friend also said to put suv on 4 jack stands and step on gas.
I dont think its ring pinion. Because it happens only on load. The ring pinion is always rotating. Thats why I believe its not the input shaft bearing on rear differential

 

[imp]

Good point. I thought auto and 4 high are basically same thing. Just 4high is manually turning on not leaving it to computer to detect slip. I was also told could be torque converter related. As stated i will try make video but its really hard to hear it. My friend also said to put suv on 4 jack stands and step on gas.
I dont think its ring pinion. Because it happens only on load. The ring pinion is always rotating. Thats why I believe its not the input shaft bearing on rear differential

"The ring pinion is always rotating. Thats why I believe its not the input shaft bearing on rear differential"

The "pinion" gear is turned by the driveshaft. The "ring" gear is solidly attached to the differential carrier, supported by two tapered roller bearings. The pinion turns when the vehicle is MOVING only, as does the ring gear. "Input shaft bearing on rear differential" implies bearings supporting the PINION GEAR only. They turn much faster than the differential bearings, 3.73 times as fast with 3.73 gear ratio. Thus bad pinion bearings make a much higher-pitched howl than bad differential bearings, which turn at wheel speed. The ring gear teeth are "spaced" apart, given clearance, from the pinion gear teeth by a small amount, typically about 0.010 inch; this is called "backlash". Upon relief of driving force, gas pedal released, the backlash allows the ring gear to basically coast, which produces no noise, or much less, if the ring gear is at fault.

 

[Gary Crist]

It would be nice if you could borrow a set of tires and rims for a test. Then
tire noise would be ruled out as a source.

 

[Apexmaster]

Hi. Yes that would be nice. I wish I could post video of noise. I did make video but noise cannot be heard. I know the difference from a bad wheel bearing noise for example. It drones inside the car. As stated when I sit in back I can barely hear the droning, but when I sit in driver or passenger seat its very loud. And feel small vibration

 

[Mr. Alligator]

Go back just for a second... What is the status of your front hubs (and rear wheel bearings)?

I ask only because this may be the most common issue here, and because in my experience the hubs/bearings fail and make a variety of sounds on the way out.

Good luck with this.

 

[Apexmaster]

Go back just for a second... What is the status of your front hubs (and rear wheel bearings)?

I ask only because this may be the most common issue here, and because in my experience the hubs/bearings fail and make a variety of sounds on the way out.

Good luck with this.

I replaced both rear hubs and bearing

 

[tcbberger]

Good morning and happy new year to all
I own 02 explorer xlt 4.0 auto. Ever since I got the vehicle it has this humming noise only from 55mph and higher. And only while on the gas. When back off gas it stops. It is a humming noise not grinding. For longest time I thought it was coming from rear, but yesterday I had my wife drive car and I sat in rear. And its not from rear. Its from front for sure. Its not wheel bearings, I check those. Transmission oil good, shift very smooth . I will try make video and post it.

That is rear end noise, trust me , back then , those stock rears had tons of problems, poor design, no cover to expose gears to view gears, you have to remove the whole rear end to look at the gears, real bright idea ford!

 

[steven434]

Good morning and happy new year to all
I own 02 explorer xlt 4.0 auto. Ever since I got the vehicle it has this humming noise only from 55mph and higher. And only while on the gas. When back off gas it stops. It is a humming noise not grinding. For longest time I thought it was coming from rear, but yesterday I had my wife drive car and I sat in rear. And its not from rear. Its from front for sure. Its not wheel bearings, I check those. Transmission oil good, shift very smooth . I will try make video and post it.

i had simuliar problem with 4.0 turned out to be idle air control valve check your intake gaskets as well