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Old 07-23-2013, 02:26 PM   #1
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Scratchy sound when on throttle

My 2.5L 98' Wrangler makes an annoying scratchy sound when I get up to speed in 4th gear or 5th. It only happens when I apply my foot to the gas pedal at speeds. Even the tiniest bit. Anybody have any ideas?

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Old 07-23-2013, 02:45 PM   #2
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How much are you lifted?
Do you have a SYE?

My guess is its your driveshaft binding slightly...happens when the load on the motor changes the angle and it wants to bind.

Generally doesnt do it lower than 35-40mph but yeah...

If its that...then you'll need a tcase drop to assit with it or the "best" way would be to add a SYE, CV Shaft, and adjustable rear lower control arms.

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Old 07-23-2013, 03:16 PM   #3
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Originally Posted by Owen_TJ View Post
How much are you lifted?
Do you have a SYE?

My guess is its your driveshaft binding slightly...happens when the load on the motor changes the angle and it wants to bind.

Generally doesnt do it lower than 35-40mph but yeah...

If its that...then you'll need a tcase drop to assit with it or the "best" way would be to add a SYE, CV Shaft, and adjustable rear lower control arms.
I'm running stock suspension on 32x12.50s. I just ordered a 3.25 Rough Country lift that comes with a t-case drop. What's SYE?
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Old 07-23-2013, 03:19 PM   #4
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Slip yoke eliminator...

you shouldnt have pinion angle issues at the moment if you're running a stock suspension. Just really sounds like a driveshaft issue (i currently have the same thing going on but am replacing everything in the next couple weeks).
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Old 07-23-2013, 03:23 PM   #5
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Wouldn't it constantly be making that noise though? It only happens between feathering the gas and flat out. If I let off, the noise stops.
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Old 07-23-2013, 03:26 PM   #6
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Nope...and thats identical to mine and its because of my driveshaft angle after my 8.8 swap

In order to fix mine i need adjustable lower control arms, SYE kit, and a new CV driveshaft.

i'd put all my chips on that being your problem...could get under there and see if theres somethign hanging it up.

If you drop your tcase a bit (maybe put some washers in there for the time being) then i bet it would go away.
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Old 07-23-2013, 03:30 PM   #7
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Well this isn't good...
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Old 07-23-2013, 03:33 PM   #8
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I just went and looked, the rear shaft is pretty much completely straight!
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Old 07-23-2013, 03:41 PM   #9
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the way i tested mine was i just removed my rear shaft...drove it; sound was gone. Put the shaft back in and it came back...

since i'm fixing it in the next couple weeks i dont really care...just more annoying than anything.
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Old 07-23-2013, 03:47 PM   #10
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Well what sucks is that I'm 16 and I'm not allowed to have job, and I just put all my money into the lift. I guess the only thing I can do is put the t-case drop on it when I get the lift, and grease up the joints.
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Old 07-23-2013, 03:53 PM   #11
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Why are you not allowed to have a job??
Kinda defeats the purpose of having a vehicle...

regardless...you could always go pull the rear shaft, put it in 4wd, then drive it to see if the noise goes away.

Maybe someone else will chime in with another option for you
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Old 07-23-2013, 03:57 PM   #12
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Could be the Ujoints?
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Old 07-23-2013, 04:03 PM   #13
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Not allowed to have a job because of school.Only got the Jeep from grades and such. But yeah I guess I'll just mess around with it and see if it'll go away. If not I can live with it.
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Old 07-23-2013, 04:06 PM   #14
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Could be the Ujoints?
If it were a u-joint would I be able to diagnose it easily? Such as just trying to move the shaft back and forth?
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Old 07-23-2013, 04:12 PM   #15
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If the noise occurs only when you apply throttle, it could be pinging due to carbon buildup in the engine. Diagnosis is easy: run the tank nearly empty, then fill it with at least 10 gallons of premium grade gas. If the noise is gone within 10 miles or so, the engine is pinging.

Diagnosis is easier than fixing it. Don't fall for any solution that has you squirting water or anything else into the intake of a running engine. Don't use Marvel Mystery Oil or SeaFoam or Carb Cleaner or magic fuel injection additives of any kind. If any of those things actually removed carbon the way they claimed, you would just plug up your catalytic converter and add $1000 or so of new converter parts and labor to your repair bill.

If it's pinging, do a compression test and a cylinder leakdown test, and see if you need an engine rebuild or just a valve job.
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Old 07-23-2013, 04:16 PM   #16
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I very highly doubt its the carbon buildup...

go drive the jeep, open your door or put the window down, and feather the gas or throw it in neutral and listen where its coming from.

Its most likely going to be coming from under the vehicle (the shaft).

I dont know why you'd be having trouble with this on a stock suspension but still, thats my guess.
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Old 07-23-2013, 04:19 PM   #17
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Originally Posted by KaiserJeep View Post
If the noise occurs only when you apply throttle, it could be pinging due to carbon buildup in the engine. Diagnosis is easy: run the tank nearly empty, then fill it with at least 10 gallons of premium grade gas. If the noise is gone within 10 miles or so, the engine is pinging.

Diagnosis is easier than fixing it. Don't fall for any solution that has you squirting water or anything else into the intake of a running engine. Don't use Marvel Mystery Oil or SeaFoam or Carb Cleaner or magic fuel injection additives of any kind. If any of those things actually removed carbon the way they claimed, you would just plug up your catalytic converter and add $1000 or so of new converter parts and labor to your repair bill.

If it's pinging, do a compression test and a cylinder leakdown test, and see if you need an engine rebuild or just a valve job.
The sound doesn't sound like it comes from the front. And I'm glad too because all of that sounds like a PITA.
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Old 07-23-2013, 04:33 PM   #18
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Don't discard my input so casually. A '98 TJ has to have high miles on it and it's a prime candidate for pinging/knocking, especially in warm weather. The diagnosis I told you about - 10 gallons of Premium gas - costs about $1 more than buying 10 gallons of regular, and no extra time at all. Why not simply eliminate this common problem before looking for a mysterious and unlikely powertrain squeak?

That "scratchy sound" you describe is classic for spark knock, aka pinging.

One other point. It is YOUR JEEP. YOU are responsible for maintaining it. People in online forums can and do sometimes give very poor advice that leads to noobies making bad decisions, to the point where they damage the Jeep. Most often the bad advice just comes from somebody with little experience, who honestly thinks that what you describe is one of the relatively few problems he has encountered on his own Jeep.

I know I am 3X the age of many people here, but I learned to drive offroad in 1970 and my 2003 is my ninth Jeep. I do know something about this.
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Old 07-23-2013, 04:36 PM   #19
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Don't discard my input so casually. A '98 TJ has to have high miles on it and it's a prime candidate for pinging/knocking, especially in warm weather. The diagnosis I told you about - 10 gallons of Premium gas - costs about $1 more than buying 10 gallons of regular, and no extra time at all. Why not simply eliminate this common problem before looking for a mysterious and unlikely powertrain squeak?

That "scratchy sound" you describe is classic for spark knock, aka pinging.
The Jeep has just over 84k on it.
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Old 07-23-2013, 04:37 PM   #20
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And I've heard the noise before. After going mudding in the past I've heard it, but it went away. This time it's not. Again, it's not from the front.
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Old 07-23-2013, 04:43 PM   #21
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You hear spark knock from the tailpipe in the rear. 84K is enough miles to ping.
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Old 07-25-2013, 10:06 PM   #22
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How can I diagnose this?
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Old 07-25-2013, 10:48 PM   #23
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I had a similar noise in my 2000. It turned being the cv in the front driveline. The ball dried up and only made noises at certain speeds.
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Old 08-06-2013, 08:53 PM   #24
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I got lifted 3.25" and dropped the tcase. It still made the noise, but quieter. Changed the t-case fluid, and that also made it quieter, lol. Maybe when I change the tranny fluid it'll sound better?

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