Mysterious noise.... care to take a guess?

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Copenhagen1

Copenhagen1

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I hate starting new threads. But I am perplexed. This noise is going to be hard to diagnose in person, much less over the web. I have studied and read and have not come across anything like this.

It started probably 10k miles ago.
-At first I thought it was just the BFG AT's getting louder at speed because they were getting older.
-It was just a low hum and increases with speed.
-There is no noise when parked or at idle sitting still.
-It is definitely drivetrain related and definitely front end.
-It now is loud enough for me to know that it is not the tires singing.
-It is a deeper hum than tires but does not really sound like grinding.
-When driving down the road at any speed, it is much more pronounced when my foot is on the accelerator. When I lift my foot and let it coast, it quiets considerably. -I have always had a vibration in my H/L transfer case shifter and it doesn't seem to be any better or worse.

I have greased my front driveshaft, checked my diff fluid, and checked for play in the wheel bearings by jacking it up and trying to wiggle the tire top to bottom.

Could I have a dry cv joint and it is groaning for grease? Is there any way I can isolate the rotation in the front end so that i can drive it down the road and listen without things turning? If I pull the front driveshaft and lock the CDL, my CV's and diff will still be turning because of driveplates?

I sure hate to start a thread like this that is going to be so hard to diagnose but I am at wits end. Let me know questions or thoughts and I will try to reply quickly with answers so that we can rule things out.
 
put all 4 tires in the air, put it in gear and crawl around under there with a stethoscope and see if you can pin point it. Problem is with no load it may not make a sound. But its a place to start.

Poke the diff on output shafts and in the middle as well as input shaft.

poke the front uprights to listen to the wheel bearings.

also poke the brake calipers, one may be dragging.

Good luck! These things are never fun!
 
What's is the condition of the spindle bearings (needle) and bushings? These are separate from the actual wheel bearings themselves.
 
I have thought about putting it in the air on jack stands and putting it in gear and listening. But that is about all I have done is thought about it. Seems pretty damn scary to do that. In my mind, it would be alright but it will be kind of hard to get my body to commit to crawling under there with all four wheels spinning.

Any thoughts from the crowd on this procedure? Would you do it?

Addressing your other suggestions..... I bought an infrared thermometer and have checked temps after driving on numerous spots.
Checked front u- joints compared to rear u-joints. Checked driveplate on left compared to driveplate on right.
Checked front pinion temps against rear pinion temps.
Checked front diff housing against rear diff housing.
Checked outer cv boot on left against outer cv boot on right.
Checked inner boots against each other as well.
Checked DS backing plate against PS backing plate.
Nothing so far has stood out.....not more than 10*F variance. The largest variance I found was rear pinion was maybe 115*F and front pinion was 125*F. It caused me to check fluid in front and it is full and fairly clear 90wt.

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SupraTuRD said:
What's is the condition of the spindle bearings (needle) and bushings? These are separate from the actual wheel bearings themselves.
Click to expand...

To answer your question..... I don't know.

About 10k miles ago, I put it in a local shop to have new brakes and rotors installed. I hate trusting my truck to someone else but was not confident in my ability to set preloads on bearings etc. etc. . The shop came highly recommended. I supplied them with oem seals but not new bearings. He said they looked fine when I picked it up.

If the spindle bearing was going bad, wouldn't the excessive heat show up at the driveplate? Is there another way for me to check the spindle bearings without tearing it apart?

Sent from my iPhone using IH8MUD
 
Per SupraTuRd: I'd, its easy enough to do and eliminate it as a concern, pull the front hubs, clean, inspect, regrease and adjust...be sure to inspect/regrease the spindle needle bearing (its easy to miss if you are not aware its there...).

How do you know its coming from the front? Driveline noises are notoriously difficult to pin down.
 
More to the story.....

I lifted this truck about 25k miles ago. I just put in 30mm spacers in rear (about 1.25") and cranked factory torsion bars to level in front (maybe 2.25").

When I first did this, my cv boots puked a little. It was enough that it scared me and I put a Slee drop diff kit in. I cleaned up the area and haven't noticed any more grease, although I haven't watched it terribly close. While searching for this noise, I have found that I now have a ruptured boot on the drivers side. Could the "birfield" be running dry and causing this noise?

Sent from my iPhone using IH8MUD
 
spressomon said:
How do you know its coming from the front? Driveline noises are notoriously difficult to pin down.
Click to expand...

Don't know for sure..... Just my gut feeling. When sitting behind the wheel, it sounds like front drivers side to me. In percentages, I am 95% sure about it being in front and about 75% sure it is drivers side but I could be wrong.

Sent from my iPhone using IH8MUD
 
Similar issue here, but was clearly rotational noise, but inconsistent. Ultimately it turned out to the be a bad front wheel bearing that displaced the brake caliper enough to cause an expensive noise when it rubbed. The techs missed the bearing the first time, but after I was able to replicate the noise the tech finally spotted the bad bearing.

In hindsight I think I was hearing a high-pitched whine that I thought was just the transmission, but was somewhat like a throw-out bearing in an old VW clutch. Spent two months driving around with no radio to try and ID the problem. Good luck...
 
Worn out spindle bearing makes a groan when the shaft starts grinding the brass bushing.
Easy to check - there are threads on the issue in here. If you check too late, your driveshaft will be "gone". (Ask me how I know:rolleyes:)
 
I know you check bearings for play, but your description sounds just like a wheel bearing that is shot.
If you are getting the groaning or humming noise, there is a part of your bearing that is damaged. They will feel tight but can still have a damaged or bad spot causng the groaning you are talking about. I used to drive a Tacoma with mud tires and it was a PITA to diagnose wheel bearings! Good luck!
 
My transmission did the same thing before it went out.... Just another thought. Mine is a 2000 year model.
 
The sound you described sounds like a bearing. Check wheel bearings to see if they're rough or "grabby" when you turn them in the race or on the spindle. U-joints will usually make kind of a "tweet" sound and will get exponentially faster with speed. I'm not familiar with birfield failure noises. Maybe someone can comment on this.
 
^Yep, strange...or not so strange that the noise stared about 10k miles ago and you had the brakes and bearings redone about 10k miles ago.?. Check the bearings, the preload may be too tight and burning up your bearings, could be too much or not enough grease. If you cv was bad you would have noticed a ton of grease everywhere like something puked under there.
 
Alright.... I spent Saturday taking apart the front left spindle assembly. I didn't find anything extraordinary in there. Grease was fresh, bearings looked good. I pushed the driveshaft towards the diff and took a look inside the spindle. I saw grease and didn't see shavings or anything that would cause alarm.

I am with y'all that it sounds like a bearing going out. At slower speeds like 30-50 it has a cyclical sound like a tire out of balance. The faster you go, it becomes more of a constant deep hum. Like a mud tire hum but not as high pitched.

My driver side CV driveshaft has a hole in the inboard boot. It is the boot closest to the diff, but the hole is the furthest away from the diff but still in that boot. In other words, that boot angles down away from the diff and the hole is on the lower end. I am fairly sure that it is drained completely of grease at this point because it does not appear to still be puking when driven.

Could the noise I am hearing be that joint running dry? The fact that it is angled would seem to indicate why the sound is cyclical at lower revolutions. ( it would still be cyclical at higher revolutions it just becomes harder to distinguish with a human ear at the higher rpm's)
If the joint has been running dry, would you just reboot and refill with grease or is it toast?
I read on here where people replace bad cv driveshafts but it seems like there is no warning sound that go along before the failure.

I am just thinking out loud. Any other thoughts?
 
Guessing that if the cv joint is actually humming, it is worn so much that it ought to be changed. Not that it cannot run another few miles, but...
 
Another piece to the puzzle..... My 17 yr old son and I were driving it to baseball practice and I was trying to get him to hear what I am hearing. I told him it was not the higher pitched hum, that is the BFG AT's, but it is the lower pitched hum. He noticed that it gets worse when I steer right. He also agrees with me that it seems to be coming from front drivers side and his vantage point was the passenger seat.

So if I am driving down the road at 30+ mph I can somewhat hear the hum. But if I put just a little right bias into the steering wheel (like changing lanes or just staying in my lane) then it definitely gets more pronounced. It doesn't get considerably louder when turning a corner though.( Although turning a corner you have to slow down enough that I can't hardly hear it anyway.)

While he was at baseball practice, I took the opportunity to lock the CDL and do some tight 360* turns. There was no clicking or popping from either side.
 
I'm still 99% sure it's a wheel bearing. Turning right would put more pressure on the left bearings which is a common symptom of a bad bearing. I know they "looked" ok but even the slightest ding in a race or spot on a couple bearings will cause alot of noise when driving. Since you know how to and have had the hub apart already, my vote is to change out the bearing w/ new races and go from there. I would be SHOCKED if that is not your problem, although the CV joint could be an issue, I still say bearings is where it's at here. Just my thoughts.
 
If that CV were dry you would see sings of montazuma's revenge amount of grease spun out of it. How are the tires wearing, do you feel a vibration in the wheel? Could it be a belt in the tire that has separated?
 
Copenhagen1 said:
Another piece to the puzzle..... My 17 yr old son and I were driving it to baseball practice and I was trying to get him to hear what I am hearing. I told him it was not the higher pitched hum, that is the BFG AT's, but it is the lower pitched hum. He noticed that it gets worse when I steer right. He also agrees with me that it seems to be coming from front drivers side and his vantage point was the passenger seat.

So if I am driving down the road at 30+ mph I can somewhat hear the hum. But if I put just a little right bias into the steering wheel (like changing lanes or just staying in my lane) then it definitely gets more pronounced. It doesn't get considerably louder when turning a corner though.( Although turning a corner you have to slow down enough that I can't hardly hear it anyway.)
Click to expand...
= Left wheel bearing
 
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