Hum/Whine Only while accelerating

[99EB5.0]

I did some searching, and didn't find much, so here goes...

Truck is a 99, 5.0 AWD

I've got a hum or whine coming somewhere from the drivetrain (i think)

Only when I'm accelerating, it quits the second i let off the gas. Suspension is all tight. Trans shifts good. Just had a seal replaced on the front diff so fluid is clean. Transfer case has fresh fluid.

It's driving me crazy and I can't figure it out.

Any ideas?

 

[Blacksheep Josh]

Are you hearing it from the truck itself or from the radio?

 

[99EB5.0]

It's definitely from the truck.

 

[99EB5.0]

And it fluctuates depending on how much I'm accelerating. It's like there is a certain amount of pedal where its loudest. More pedal, its quieter until I let off until its to that spot. No pedal, silent. Speed doesn't matter...

 

[M Penwald]

I have the same thing. It's a gear train or driveshaft whine but I can't diagnose it yet. Sounds like mine is coming from the center case.

 

[MonsterTruck460]

Probably a bad u-joint. Any shaking under accel?

 

[99EB5.0]

@penwald- mine sounds more like its coming from farther forward than the transfer case.

@monstertruck- no noticeable shaking. I have a small clunk when putting it into reverse so ill check out the ujoints. What kind if symptoms would I expect from the cv joint going bad on the transfer case end of the front driveshaft?

 

[99EB5.0]

I had a bad wheel bearing I replaced so I don't know how long this noise existed simultaneously with the noise from the bearing. I'm only assuming Ford put the proper fluid in the front diff when they replaced the pinion seal...

 

[Benji-Man]

I have the 4.0 a4wd and had the same sounds and after replacing both front bearings, all u joints, ended up going to replace a leaky rear axle seal. When I pulled the c clips and removed the axles, the differential carrier bearing damn near fell out. That was with 125,000 miles on the truck. It does it's share of hauling. It's now been 45,000 miles since... sound is still gone. Just sayin'..... Worth a look.

 

[99EB5.0]

@ benji- any info on how i would check this?

 

[Benji-Man]

Drain and inspect rear diff fluid for metal shavings mine looked like glitter oil. While the rear cover is off look for signs of wear on the ring gear or see if you can move/shift the carrier, because there shouldn't be any play

 

[99EB5.0]

The noise you had...did it sound like it was coming from the rear? Because mine definitely sounds like its coming from the front somewhere

 

[Benji-Man]

Mine always sounded like it was coming from the front, i guess that's just the way sound travels. That's why i changed the front wheel bearings first, then all the u joints. I will say this though, the rear carrier bearing wear had gotten so bad that when I was on the highway and going 75+mph if i shifted lanes, the ABS light would illuminate since the speed sensor on top of the rear diff would loose signal with the tone ring on the ring gear. Again mine was extreme, it took me that long to find it. Started noticing the sound at 90,000 miles

 

[99EB5.0]

Update.

I pulled my front driveshaft and drove around the block...
All noises I heard before were non existent. Humming while accelerating, and a metallic noise i heard when accelerating and coasting.

Also, my driveshaft rattles, like something is loose inside?

Thoughts?

If the front diff were my issue would it make the noises driveshaft in or out?

 

[Turdle]

http://www.explorerforum.com/forums/showthread.php?t=315717&highlight=awd+drive+shaft

Been fighting this one a while now eh?

You might try a rebuild of the cv joint on the transfer case end, as this is what the re-builders do. There is a thread with the information somewhere on the forum.



Good luck.

 

[99EB5.0]

http://www.explorerforum.com/forums/showthread.php?t=315717&highlight=awd+drive+shaft

Been fighting this one a while now eh?

You might try a rebuild of the cv joint on the transfer case end, as this is what the re-builders do. There is a thread with the information somewhere on the forum.



Good luck.

Yes! I have, I know I need to take care of the cv joint end, but am more focused on what's causing the humming up front.

 

[Turdle]

You took it out, and it rattled, so you went for a drive with it out and the noise is gone. I would say from 500 miles away, you need either a rebuilt drive shaft or a rebuild kit. If the cv is worn and damaged it will be off balance at the least.

There are other things to consider ,
tire size-(wear) mis match, transfer case wear , and yes even the front diff could be causing an issue, but unless you repair the front drive shaft you will never know.

 

[99EB5.0]

I'm picking up another driveshaft tomorrow. I found a guy locally selling a front diff off of a 97 4.0 4wd explorer. Did these come with the d4 front diff's? Even if the driveshaft fixes my issues, he only wants 75 for the front diff and claims its out of a 60k truck, ill know for sure tomorrow, it wouldnt hurt to have an extra for that price.

 

[RomeovilleIL]

Make sure it has the same gearing as yours. With the 5.0 AWD you likely have a 3.73, but check the sticker on the door jam to be sure. A lot of the 4.0's have a 3.27. I assume the purpose of your purchase is to avoid buying new internals and going through the rebuild/regear so getting the spare may not be useful.

As for the propshaft, take your original with you to match them up. There are 2 different lengths in use & they are not interchangeable. If you get a reman or new should be good to go. If it's a used pull, it can be a crap shoot - test the cv by moving in a circle both directions. Should move smoothly with no "sticky" points and definitely not feel loose or be floppy. If a used cv checks out ok do yourself a favor and get a new u-joint on it as a $15 insurance policy. The originals were sealed so can guarantee it was never serviced and they are difficult to gauge wear.

 

[sw3ns]

Any ideas?

I found it!@#$ at least on mine. (05 v8). this thing was buggin me ever since i purchased it (my 3rd ex now). everything else was fixed up but this whistle just wouldnt quit. I had read countless threads like this all with no resolve, and will be replying to as many as i can find with this info, but it was narrowed down to the air intake as mine would start/quiet down depending on the gas pedal position. after tearing thru all the upper intake stuffs, i just started grabbin and yanking hoses fidgeting with everything i could reach.

Finally, i found that i could change the pitch first by compressing the MAF (big air intake tube rgt?) but also an airline that runs from the intake body to the brake booster. on the brake booster end the valve or plug or w/e it is was weathered and had a couple hairline cracks. thru some rtv on it to test temporarially and sure enough the whistle was gone, best thing i hadnt heard all day . cleaned it off sealed it up with some epoxy and just got back from a round trip phx to la and didnt hear it once. hope this helps anyone else having the same issue. gl