Calling Jeep sound detectives: whistle / squeal / whine

B00mb00m

B00mb00m

The Church of Cutting Brakes of Atlas-Front Digs
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Ok guys I need help. This squeal might be getting worse and I'm about to do a big wheeling trip. Need to figure out if this is something failing.

Here's a video, sounds starts around 12mph accelerating and ends around 10mph decelerating.

Things I know:
  1. Not rpm dependent. Does not change pitch with RPM.
  2. Not dependent on engine load (squeals coasting downhill).
  3. Not dependent on transmission gear, it might go away at highway speed or it might just be that road noise drowns it out.
  4. Not throttle dependent **but sometimes seems to go away briefly under throttle changes.
  5. Requires a minimum speed. Seems loudest at low speeds surprisingly.
  6. Does not appear when engine is cold. Seems to need to drive for 30 minutes or so. Shows up on longer drives. Once squealing continues squealing even after stop / short shutdown. This makes me think not a aerodynamic whistle. Also the fact that it doesn't change pitch with speed.
  7. Just tried this and I don't think it squeals / whistles in reverse??
  8. Not affected by 2wd / 4wd.
  9. I'm running doors off right now and it appears to be coming from front and louder on driver side.
Vacuum leak?? I'm at a loss. But I would think vacuum leak would be apparent when vehicle is stopped also.
 
Rich1961 said:
Driveshaft U-Joint? Pull the front drive shaft and see if the noise is still there.
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I'll have to get it to make the sound again and try but wouldn't a UJ sound change with higher RPM?
 
Broken clip holding the pads?

On #6 you say even after short shutdown. I'm assuming this means it returns after you restart and drive, not that the noise actually continues AFTER short shutdown, right. As in you turn the engine off and the noise continues.

You have a guess if noise is in the front or back? Have a kid ride with you. They have much better hearing.
Could be a bearing in the front accessory belt. Tensioner idler or even power steering pump? Needs a load on the belt to make noise? P/S high pressure relief? With no audio or even area to start at it's a big guess. Hope any of these might do the trick.
 
Goatman said:
Broken clip holding the pads?
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But wouldn't the whistle stop when brakes are applied?

I'm assuming this means it returns after you restart and drive, not that the noise actually continues AFTER short shutdown, right.
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Yes that's what I meant to say., After I restart and drive.

You have a guess if noise is in the front or back?
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I had the whole fam with me, I think it is coming from the front. Can't tell engine or axle or what though. The serp belt / tensioner might be a thought. I'm going to pickup a new alternator, belt, idler and tensioner. Throwing parts at it. I'm ok throwing parts since those are good preventative things to do anyway, I have only replaced the belt since I owned it. I was doing a bunch of reading on similar noise and one guy notes a loose belt can let air under the belt and whistle.
 
Apparition said:
Link works for me sounds like an air leak whistle
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Ya thats what i think also. Whats strange is that its "on/off" so to speak, does require a minimum speed but doesn't change pitch with speed. I'm glad to be trailering to the camp spot this weekend so its not a 4 hour drive in the jeep wondering whats wrong.
 
B00mb00m said:
Ya thats what i think also. Whats strange is that its "on/off" so to speak, does require a minimum speed but doesn't change pitch with speed. I'm glad to be trailering to the camp spot this weekend so its not a 4 hour drive in the jeep wondering whats wrong.
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You check your intake and throttle body well?
 
Apparition said:
You check your intake and throttle body well?
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I tightened throttle body already and didnt change. You thinking the intake manifold to the block also? I haven't done that.
 
B00mb00m said:
I tightened throttle body already and didnt change. You thinking the intake manifold to the block also? I haven't done that.
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I don’t know, I’d be looking anywhere that would be affected by a minimum RPM. I’ve never had to troubleshoot anything like that before. Can you have someone else run the throttle while you listen to try to pinpoint the sound?
 
Apparition said:
I don’t know, I’d be looking anywhere that would be affected by a minimum RPM. I’ve never had to troubleshoot anything like that before. Can you have someone else run the throttle while you listen to try to pinpoint the sound?
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Problem is it has to be moving! That makes troubleshooting noise sources really difficult. I'm going to do belt and idler to start.
 
B00mb00m said:
Problem is it has to be moving! That makes troubleshooting noise sources really difficult. I'm going to do belt and idler to start.
Click to expand...
I took minimum speed as rpm.

If it’s a moving thing then it may have to do with airflow through the engine bay. Could test it by blocking the radiator off with cardboard for a quick drive. If that doesn’t change anything then hood gap or air from underneath could do it.

Just spitballing
 
Apparition said:
I took minimum speed as rpm.

If it’s a moving thing then it may have to do with airflow through the engine bay. Could test it by blocking the radiator off with cardboard for a quick drive. If that doesn’t change anything then hood gap or air from underneath could do it.

Just spitballing
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Ordered a DB electrical alternator off of Amazon. I'll pack it as spare for my trip. I did swap the idler pulley and belt today and ordered a new Mopar belt tensioner also. All these things look original. Except alternator which has 2013 stamped on it. My gut says something vacuum related.
 
Ok good update. This noise has been getting louder I would say. It still does t start until the vehicle has been driving for a while. Not engine temp dependent. Takes about 15 min of driving or highway speed to make it start squealing. It's not noticeable above about 40mph and it goes away below 10mph.

1.First had my wife drive at 10mph and i jogged beside the rig. It sounded like it was coming from under the jeep, transfer case area.
2. Brought the jeep into my garage and put the rear axle on jack stands. I really don't like to do this. Had my wife drive the vehicle. The squealing started so it's not an aerodynamic issue. I crawled my dumb ass under the vehicle and took this video:
3. 99% of the time the squeal would start when transmission shifted to second. That got me sweating hoping it wasn't the transmission. The other thing that pointed to transmission is that there is no squeal in reverse.
4. I pulled the rear driveshaft though and the squeal went away so more than likely that means CV joint. When I removed the axle shaft I realized there are flush mount zircs for the CV. Ya..... Didn't realize that needed to be greased. The good thing is the ball doesn't seem sloppy. So I'll regrease it and see if the squeal goes away. Hoping that's the ticket. I'll report back.
 
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The plot thickens:

Well I greased the centering yoke and reinstalled... And the squeal is still there. Noooooo. I can't tell *maybe* it's a bit quieter or maybe it's my mind messing with me. The two things that are confusing are, 1, the squeal doesn't happen in reverse and 2, it doesn't happen until something warms up. Like I can drive around town < 50mph and the squeal doesn't start but once it starts like if I run on highway and then back into town it will start at around 10mph.

I was at the metal shop next door to drivines NW so I stopped in and showed them the squealing video. He agreed seemed like centering ball/bearing. So I went home pulled the DS then brought it back. He was surprised to find no notable slop and said he didn't think the CV Was the source based on that. I said to rebuild it anyhow since the troubleshooting was pointing to driveshaft or rearward.

Since the squeal stopped after driveshaft removal I would assume something in the diff may be the source if not the driveshaft.

Anyone rig up a drill to drive a rear diff for troubleshooting purposes?
 
Fuuuuudge.

Got the driveshaft back from Driveline NW. I talked to the salty old mechanic there. He said he went through the whole thing everything in the driveshaft looked fine. He regressed every uj cap and added a rubber dust seal to the centering ball.

I also cracked open the fill port on TC and it was full, actually let a bit run out as it seemed over filled.

Sure enough 20 minutes of driving and the squeal started to return.

I have a couple things to check. 1. Disconnect driveshaft and TC Yoke remove yoke and regrease and reinstall. Maybe the seal is squealing??

I'll go drive it 20 minutes to get the squeal warmed up then pull the rear drive shaft and drive again. If it goes away then I'm really at a lost for ideas. If not then I'm assuming rear diff.

But as another check I will reinstall rear driveshaft and remove front drive shaft.

The weird thing was when I removed rear drive shaft on jack stands the squealing went away.
 
By the way I should clarify, I'm ALL FREAKINH EARS if someone has other solutions
 
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