Let's play "What's that Awful Sound?"

So I keep getting this intermittent howling/growling sound coming from the the front center/passenger side of the car as soon as I hit 55-60mph, and it continues up to 70mph (haven't gone faster than this). I'd say it sounds like when you hit the rumble strips on the side of the highway, only quieter. There's a slight vibration with the sound, which is felt in my seat the most. It comes and goes when I'm in the 55-70mph range, and seems to do it at random i.e. speeding up/slowing down or turning the steering wheel doesn't do anything.


Causes that I have ruled out:

- Front Shocks: New one's put on since sound--no change.
- Front pass. wheel bearing: New one put on since sound--no change.
- Front brakes: New pads/rotors put on since sound--no change.
- Exhaust hitting crossmember: All exhaust hangers are in good shape and there's plenty of clearance.
- Alignment: Alignment done since sound--no change.
- Tie rod/track bar: New beefy units put in since sound--no change.
- Lower control arms: Bushings are great. Has aftermarket fixed arms like Rough Country.


Things that I think it may be:

- Tires out of balance.
- Engine issue (slight misfire at idle that I'm chasing, but still runs just fine overall)
- Transmission issue (when I press in the clutch, sound remains. I do believe I have loose flywheel-crank bolts/loose pressure plate bolts as I get a separate metal rattling sound coming specifically from the transmission)
- Front diff: I opened up the fill plug and the fluid was pretty sludgy. Maybe incorrect front/rear gearing. I was also told the front/rear has 3.73s, but I don't know how much merit this holds as a lot of the mods done previously were done half-assed, and the seller said it had a D35 in the rear when it's clearly an 8.25. I do get 17-18mpg in mixed driving on 32s, so I don't think it still has the 3.07s in it.
- Major exhaust leak that I can't see

It's driving me nuts, especially since I have to drive on the highway 80 miles twice a week. I have to turn up the radio because it sounds like something is going to blow up and scares the crap outta me.

Is your rig lifted? That sounds like my jeep, which is lifted and in desparate need of a SYE...I would check driveline angles (if lifted) and u-joints.:eyes:

Zapthepunctual said:

Is your rig lifted? That sounds like my jeep, which is lifted and in desparate need of a SYE...I would check driveline angles (if lifted) and u-joints.:eyes:

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X2

Mine groans from 30+ and it is the angle of the rear drive shaft.

I've had the same issue with a Ford Exploder AWD for some time. I finally tracked it down to a bad front output shaft bearing on the transfer case.

Thanks for the input guys. Forgot to mention I have a 3" lift with a 1.5" transfer case drop. I checked the front axle U joints when I did the brakes and they were fine. The rear driveshaft U joints are fairly new and have no play. Ill have to check the front driveshaft U joints as well as the output shaft.

The Jeep did have a 242 conversion done by the P.O. as well so maybe something wasn't done right there.

-What year is the jeep?
-What trans is in the jeep?
-Do you have a SYE?
-Does it happen when the jeep is coasting in neutral at 55-70, or only under load?
-Is it rpm dependent or speed only?
-Do you have any shims under your leafs?

If it's mostly in the seat, it' usually something in the rear. Which makes me think you need an SYE. Rotate your tires and see if it gets any better. If it were gear mis-matching, it wouldn't matter in 2wd. But as soon as you yanked the ugly stick (or shortly thereafter), you'd grenade the t-case. If it's only under load, it could be one of many bearings in the drivetrain. If it's PURELY speed related, chances are it's nothing with your motor, and rather something in rotation that's getting thrown out of balance. If it was engine related it would do it at the same rpm/load no matter what the wheel speed. You obviously know a good number of issues with your rig, I'd say start knocking them out one by one and get back to us. We can't say "OH I KNOW WHAT THAT IS!!" when you have a laundry list of possible problems.

yank the front shaft and see if it still does it.

You're gonna laugh about this one but check to make sure there isn't a loose fender liner or flare or something that's blowing back under highway wind forces and rubbing on the tire, too.

If the noise is gradually getting worse? I would check the front wheel bearings. I had 1 that sounded just like what you described.

DanMan2k06 said:

-What year is the jeep?
-What trans is in the jeep?
-Do you have a SYE?
-Does it happen when the jeep is coasting in neutral at 55-70, or only under load?
-Is it rpm dependent or speed only?
-Do you have any shims under your leafs?

If it's mostly in the seat, it' usually something in the rear. Which makes me think you need an SYE. Rotate your tires and see if it gets any better. If it were gear mis-matching, it wouldn't matter in 2wd. But as soon as you yanked the ugly stick (or shortly thereafter), you'd grenade the t-case. If it's only under load, it could be one of many bearings in the drivetrain. If it's PURELY speed related, chances are it's nothing with your motor, and rather something in rotation that's getting thrown out of balance. If it was engine related it would do it at the same rpm/load no matter what the wheel speed. You obviously know a good number of issues with your rig, I'd say start knocking them out one by one and get back to us. We can't say "OH I KNOW WHAT THAT IS!!" when you have a laundry list of possible problems.

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1997 Sport, AX15, 4.0, 242. No SYE, no change if I push the clutch in or if it's in gear. Only speed dependent, doesn't matter the RPM. No shims in the rear.

I wasn't really looking for a definitive answer, but more of ideas that I may have overlooked. If someone had the same issue and knew what it was, great, but I know it's hard to diagnose something through words 2nd hand.

kastein said:

yank the front shaft and see if it still does it.

You're gonna laugh about this one but check to make sure there isn't a loose fender liner or flare or something that's blowing back under highway wind forces and rubbing on the tire, too.

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I was thinking about doing this, though the sound doesn't get worse or better when putting it in 4WD Hi.

I did the bushwacker flat flares so they are all trimmed or tucked away, so I doubt it's that. Thanks for the idea though!

Va Hillbilly said:

If the noise is gradually getting worse? I would check the front wheel bearings. I had 1 that sounded just like what you described.

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I replaced the passenger front hub/bearing as that's what I was convinced it was, but it made no difference. The bearing was on it's way out anyway as it fell apart once I took the old hub assembly off, so I'm glad it was replaced, but I was really hoping that's what it was.

I'm going to get under there and start yanking at everything to see if anything has any play. This one might be going to the mechanic, though. Thank you everyone for your suggestions thus far.

kastein said:

yank the front shaft and see if it still does it.

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This... pull the front shaft and drive it. Or, you need to shim the rear axle pinion up a bit to decrease the driveline angles.

One of the SEC members recently had some issues, although his has a front Aussie. He discovered that even in 2wd, his 242 was turning the front output shaft enough to cause an issue. Might be worth a pm to UNCC 99XJ and ask him exactly what it was.

Spawn 93 said:

One of the SEC members recently had some issues, although his has a front Aussie. He discovered that even in 2wd, his 242 was turning the front output shaft enough to cause an issue. Might be worth a pm to UNCC 99XJ and ask him exactly what it was.

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It's not the 242 that's turning the front output shaft, but rather the front driveshaft that's being turned by the front wheels (even in 2WD) that's turning the TC's front output shaft. The 242's did not come with the axle disconnect that some of the earlier 231 did. So, to eliminate front output shaft or front DS as the culprit, remove the front DS and drive it...see if it's any different.

Sorry Flyfisher, I wasn't clear. Tim jacked the jeep up and removed the front shaft, front output was turning with jeep in drive. IIRC, that's the story. When I fire up the laptop tomorrow, I will post a link to the these. If Tim wasn't in Italy for business, I am sure he would be able to relate his story to you himself. Just shooting out ideas here anywho.

UNCC_99XJ said:

Got a couple more heads together and we're all in agreement that since I have a NP242, it's the coupler in the case for the full time option that's still sending a little bit of power to the front. I had planned to eventually swap in a 231 anyways, so I guess i'll speed up that process.

Also discovered the pinion bearing is bad on the front end, so I can imagine that's probably not helping things either. For now, when I have to drive it, the front shaft is out and only put back in when I need it.

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I found it! While on my phone at that.....

And it wassss??????

Spawn 93 said:

Also discovered the pinion bearing is bad on the front end, so I can imagine that's probably not helping things either. For now, when I have to drive it, the front shaft is out and only put back in when I need it..

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When my 2001's front pinion bearing went bad; finding the noise took a long time.
Removing the front driveshaft did not eliminate the noise, since the gears were still spinning.
Removing the inner axle shafts, along with the driveshaft finally silenced the noise. When spinning the front yoke by hand, the bearing felt OK but when disassemble, the races had visible damage.
Finding bad bearings in the axles can be a frustrating task. Noises can telegraph to other locations, confusing the situation even more.

I need to get a contact microphone and wire it through an amplifier and headphones and use it to pinpoint noises, I have never owned another vehicle that developed so many hard to find noises.
Of course, I have never beaten another DD as badly, well with the exception of my old Baja Bug.

I took out the front driveshaft and drove it on the highway tonight. No more noise! Ok, great, so I have it down to a problem with the front diff, transfer case, or the driveshaft (U-Joints). The u-joints seem to be ok and have no play in the yoke, however.

lazyxj said:

I have never owned another vehicle that developed so many hard to find noises.

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I know. It's such a pain trying to pinpoint problems sometimes. I think a sound is coming from the front when it's really the middle, or the left when it's really the right.

Just a little follow-up. Been super busy so I haven't had a chance to do anything. Today I went and grabbed the driveshaft to have a closer inspection. After sitting for a little, it seems the one U-joint has gone to crap. It barely moves, so I'm going to have to replace that. The front pinion as well as the input yoke on the transfer case are in great shape. They both spin perfectly, have zero play whatsoever, and no leaks. I'm going to put in a new U-joint, bolt it up, and I think my problem will be solved.

Here's a video of me trying to move the U-joint:

http://www.youtube.com/watch?v=mz72OWUSa4M