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Unread 04-15-2012, 08:37 PM   #1
pman
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Clutch noise: In neutral with pedal disengaged

Have any of you had experience with your clutch making a "lop-lop-lop-lop" sound with the transmission in neutral and the clutch disengaged? The sound disappears when you depress the clutch pedal. I've tried to research it, and I've come up with two possibilities:
1) input/pilot shaft bearing problem
2) I've got to find the specifics again, but I read something this weekend online that suggested the "rubber" on the center of the clutch could be worn?

The drivetrain is a 304 mated to a T150 w/ a Dana 20 TC. I just purchased this CJ5 from a neighbor a few weeks ago, and have been elbow deep in body work, and am now going through the mechanicals. I'm wondering if this problem could also be why I have drivetrain vibes when get over 20mph (Edit-UJoints have already been replaced to no avail).

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Unread 04-15-2012, 08:57 PM   #2
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The most common cause of in neutral, clutch out noise is the throwout bearing going bad. To replace it you need to pull the tranny.
"Drivetrain vibes" while moving are usually caused by driveline u-joints going bad.
Your best bet is to check these first.
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Unread 04-15-2012, 08:57 PM   #3
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Sounds like the throw out bearing to me.
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Unread 04-15-2012, 09:04 PM   #4
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Thanks guys. Shiftace, I should have mentioned that the Ujoints were the first things I changed out. I thought for sure that was the problem with the vibes. I'm still chasing down other possible culprits, but wondered if the clutch thumping could be the issue.

On the throwout bearing, I thought "pedal in" was usually where this reared it's head? It's quiet when depressed, and shifts smoothly. Looks like I'll be pulling the tranny.
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Unread 04-15-2012, 09:38 PM   #5
Shiftace
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When you push in the clutch it loads the bearing, preventing it from rattling.

Since you already changed the u-joints to no avail, you may want to jack the rear wheels off the ground, place the Jeep in gear with the motor running(rearend blocked up and in two wheel drive, of course!) and watch all the moving parts for unusual shaking or elliptical motion. Be sure to include the tires and rims in your inspection.
Also, with the motor off, shake the slip joints. They can cause the same symptoms also.
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Unread 04-15-2012, 10:21 PM   #6
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The clutch "chatter" when you start off in first? Kind of jumps and shimmies and shakes until you get going?
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Unread 04-15-2012, 10:26 PM   #7
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Quote:
Originally Posted by Skerr
The clutch "chatter" when you start off in first? Kind of jumps and shimmies and shakes until you get going?
When this happened to me I though it was actually my engine bogging from being poorly tuned, but my throw out bearing was a total mess... The outer face part actually was able to move around the bearing like an orbital sander and it would vibrate like it was off-center until it centered itself

Put a new one in and I can start in second without any chatter at all.
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Unread 04-15-2012, 11:16 PM   #8
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Based on the info given, my first guess would be the front bearing in the transmission. A throwout bearing shouldn't be rattling around as when the clutch is out, the face of the bearing is off the diaphragm fingers. The chatter could be a combo of a bad pilot bushing and a bad front bearing which would allow the clutch/input shaft to flop around off center.
Another good transmission test is to put the t case in neutral and run throw the gears. Gently feather the clutch out for the higher gears. A wooden stick to the ear will allow a little more of a pin point as the parts in question will be moving.
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Unread 04-16-2012, 05:55 AM   #9
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Quote:
Originally Posted by only in a jeep cj View Post
Based on the info given, my first guess would be the front bearing in the transmission. A throwout bearing shouldn't be rattling around as when the clutch is out, the face of the bearing is off the diaphragm fingers. The chatter could be a combo of a bad pilot bushing and a bad front bearing which would allow the clutch/input shaft to flop around off center.
Another good transmission test is to put the t case in neutral and run throw the gears. Gently feather the clutch out for the higher gears. A wooden stick to the ear will allow a little more of a pin point as the parts in question will be moving.
I had a little more "quality" reading time on the clutch last night and I keep coming to the same conclusion regarding the front bearing. I'm traveling to FL this week so I wont be able to tear into this until later, but I'll keep everyone updated.
Skerr- The noise is there ONLY at idle/in neutral/clutch pedal out. No noise when under way, shifting or when the clutch pedal is pushed "in".
Shiftace- good point on the jackstand test. I'm laughing thinking of the "hey y'all watch this" moment if it fell off the stands.
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Unread 04-16-2012, 06:35 AM   #10
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Quote:
Originally Posted by pman View Post
I'm laughing thinking of the "hey y'all watch this" moment if it fell off the stands.
Be sure to have a video camera running!
As only in a jeep cj mentioned, it is quite possible that your front bearing went out and is causing all the symptoms you are describing including the driveline vibes. Bad u-joits and throwout bearings are only the most common causes.
Either way, you'll need to pull the tranny to know for sure.
Might as well surface the pressure plate and replace the clutch, pilot bearing, throwout bearing and front seal while you're there.
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Unread 04-18-2012, 06:27 AM   #11
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I'm curious to know what you find out.
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