sounds like scratching on a blackboard... - JeepForum.com

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post #1 of 16 Old 06-25-2013, 03:51 PM Thread Starter
ROTTEN
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sounds like scratching on a blackboard...

I got some crazy noise happening I cant figure out. While at about 2, 000 rpms with clutch in but no gas I get this weird sound. I also coasted down a big hill with the engine off and I can hear it. At first it sounds like small rocks bouncing off the side of the jeep. Then it makes this scratching/metallic noise like on a black board. O
I can hear it from underneath to the back. Problem is I can only hear in one ear and my buddy cant pinpoint it either.
Im only looking for things I should check that I didnt think of

I checked the front ujoints and hubs
Shook the exhaust around
Shook around anything that might make a noise from vibes
Jacked up and spun the back tires
Checked for play in the pinion and drive shaft
Checked drive shaft joints
Checked for nuisance rocks
I also dropped in my magnet on a rod device in the diff. Was checking the best I could for metal shavings or chunks. Someone stole my tools so I couldn't pull the cover.

Any more ideas?


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post #2 of 16 Old 06-25-2013, 05:49 PM Thread Starter
ROTTEN
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Put it up on jack stands and let the wheels roll. No sounds from what I hear. I believe its the exhaust. Im over obsessive about it!

Thx for the replies!

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post #3 of 16 Old 06-25-2013, 05:51 PM
idaholtby
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Definitely sounds drivetrain/chassis related as this happens with the engine off while coasting. You may have ruled out the most common causes. Does this happen at any speed? What condition is the slip yoke in? Any slop?
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post #4 of 16 Old 06-25-2013, 07:45 PM Thread Starter
ROTTEN
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Happens at around 2, 000 rpms or when im downshifting.
I have a stock drive train.
Like I mentioned though I had it up on stands and had it in first and letting the tires spin it didnt make the sound but revving it high did as I let off the gas.
We then took it off the stands and put it in neutral and revved it high and let off and could here it.

So...?

Having it coast off mightve just been a rattle I guess. No clue.

I just had my manifold to cat pipe replaced and on the way home it started this noise

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post #5 of 16 Old 06-25-2013, 08:07 PM Thread Starter
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Oh yeah any speed when slowing down but the scratching always sounds the same doesnt get any faster or slower with speed.

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post #6 of 16 Old 06-25-2013, 08:26 PM
gunshw301
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Might seem obvious to check but you did not mention it yet. How are your brakes?

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post #7 of 16 Old 06-25-2013, 08:39 PM Thread Starter
ROTTEN
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Rears are a year old. Im thinking of checking them next. Maybe something got loose? Super clean rig so it makes things easier to look at. Wish I could hear better. Hard to hear over the tire hum with the soft top making noises

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post #8 of 16 Old 06-25-2013, 09:22 PM
gunshw301
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Might be a sticking brake caliper. I would check.

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post #9 of 16 Old 06-25-2013, 09:25 PM Thread Starter
ROTTEN
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Funny you say that. I noticed 2 things about the front wheels. One didnt spin as much as the other. And also when it rains my fronts get really grabby and make the same type of noise. Hmmm

How do I check for a sticky caliper?

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post #10 of 16 Old 06-25-2013, 10:06 PM
idaholtby
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A sticky caliper will be super hot after a drive. Plus you should notice a pull to the opposite side when breaking as the hot/bad caliper will lose it's breaking power when hot. If it is bad enough, if you were to spit on the wheel, it will sizzle. I have never known this to be a noise issue though unless the linings are completely shot.
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post #11 of 16 Old 06-25-2013, 10:24 PM Thread Starter
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Oh I have nothing like that going on. If I did have that I would've already replaced it all.

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post #12 of 16 Old 06-26-2013, 06:20 AM
Siva283
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Whats the condition of the clutch? Throwout bearing in particular? Also any slop on the transmission input shaft. Try putting the tcase in nuetral and leave the trans in gear and coast down a hill again and see if it does it. This will help narrow down the area since only from the transfer case back would be spinning.

Edit: If the noise is still there with the trans in gear and the transfer case in nuetral there is a good chance you are experiencing chainslap for a worn chain in the tcase.

1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

Quote:
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I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim
Quote:
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. It started with a $200 axle, and a few thousand dollars later I was done :)
Quote:
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diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

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this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
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post #13 of 16 Old 06-26-2013, 06:44 AM Thread Starter
ROTTEN
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Clutch seems good to me.
Im hearing the noise when I first start it because it goes to a higher rpm. It sounds like small rocks hitting. Not a slap or grind or clunk.

I dont need to leave my driveway to make it happen. Can I just put the trans in first and tcase in neutral in my driveway?

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post #14 of 16 Old 06-26-2013, 02:06 PM
Siva283
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Quote:
Originally Posted by ROTTEN View Post
I dont need to leave my driveway to make it happen. Can I just put the trans in first and tcase in neutral in my driveway?
Yes you can. This will isolate tcase drive shaft and rear dif.

1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

Quote:
Originally Posted by Magnum View Post
I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim
Quote:
Originally Posted by ldso View Post
. It started with a $200 axle, and a few thousand dollars later I was done :)
Quote:
Originally Posted by Luuca View Post
diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...
Quote:
Originally Posted by Overhead View Post
this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
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post #15 of 16 Old 06-26-2013, 02:53 PM Thread Starter
ROTTEN
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Location: SGF
Posts: 768
Cool. Just did it. Neighbor started *****ing. Lol... old people

I have to get it about 3, 000 rpms in first to hear it. Again hard for me to hear it. I went up a few good long hills and shifted and it didnt have problems with the clutch.

Im thinking its my exhaust. I cant check the input on the trans can I?

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