Help Diagnose a rotational noise
Thread Starter
Team Owner
Joined: Jun 2001
Posts: 23,375
Likes: 1,067
From: Virginia USA
Help Diagnose a rotational noise
"71 350 Muncie 4-speed.
I replaced the clutch last fall and it's working great. I've got over 1500 miles on it and have not had any problems. The other day I was sitting at a light and I was in neutral waiting with my foot off the clutch. When I pressed the pedal I heard a strange noise. It didn't do it again the rest of the day.
Yesterday I came home and since I have to manually open my garage door (I'm cheap and don't have an automatic door opener) so I put it in neutral. When I pressed the clutch in I heard the noise again. I started troubleshooting and this is the symptoms.
Trans in neutral clutch out. Press clutch and it makes the noise for a few seconds then stops. My only thought is the input shaft bearing on the trans is starting to go because as the input shaft stops spinning because the clutch pedal is pressed the noise goes away.
Make sense?
I'm going to look at it more closely this weekend just wanted to get your opinions and/or suggestions.
If it turns out to be the bearing how difficult (other that removing the transmission
) is it to change it? Does the trans need to come completely apart and are there any special tools involved?
I replaced the clutch last fall and it's working great. I've got over 1500 miles on it and have not had any problems. The other day I was sitting at a light and I was in neutral waiting with my foot off the clutch. When I pressed the pedal I heard a strange noise. It didn't do it again the rest of the day.
Yesterday I came home and since I have to manually open my garage door (I'm cheap and don't have an automatic door opener) so I put it in neutral. When I pressed the clutch in I heard the noise again. I started troubleshooting and this is the symptoms.
Trans in neutral clutch out. Press clutch and it makes the noise for a few seconds then stops. My only thought is the input shaft bearing on the trans is starting to go because as the input shaft stops spinning because the clutch pedal is pressed the noise goes away.
Make sense?
I'm going to look at it more closely this weekend just wanted to get your opinions and/or suggestions.
If it turns out to be the bearing how difficult (other that removing the transmission
) is it to change it? Does the trans need to come completely apart and are there any special tools involved?
Race Director
Joined: Oct 2008
Posts: 19,230
Likes: 1,672
From: Long Island
I get a noise in my 85. It's the clutch fork rubbing on the throw out bearing. The clutch fork is a sloppy fitting when cold on to my throw out bearing. It stops when the clutch is disengaged - pushed in.
The throw out bearing usually makes noise when it starts to fail. Usually when the clutch is disengaged as there is a load on the bearing.
To change the bearing you have to remove the trans and bell housing.
The throw out bearing usually makes noise when it starts to fail. Usually when the clutch is disengaged as there is a load on the bearing.
To change the bearing you have to remove the trans and bell housing.
Last edited by BLUE1972; Mar 22, 2017 at 08:33 PM.
Thread Starter
Team Owner
Joined: Jun 2001
Posts: 23,375
Likes: 1,067
From: Virginia USA
Throwout bearing is new. The noise happens when I disengage the clutch (push the pedal to the floor). I would think if it's the throwout bearing the noise would not go away while the clutch is disengaged as the bearing would be spinning because it's in contact with the pressure plate fingers. This noise stops after a few seconds of clutch disengagement.
Ahhhhh, I don't want to take the trans out but it looks like I'm going to have to. I looked at my Muncie parts book and if it is the main shaft bearing it appears it can be replaced without tearing the trans apart.
Ahhhhh, I don't want to take the trans out but it looks like I'm going to have to. I looked at my Muncie parts book and if it is the main shaft bearing it appears it can be replaced without tearing the trans apart.
Racer
Joined: Jun 2016
Posts: 336
Likes: 29
From: Il.
When you're setting and you're foot is off the clutch the bearing stops spinning so when you first put you're foot down the bearing it has to speed up to the clutch also putting pressure on the bearing if it's going bad that first few spins could be whats making the noise.Sometimes a bad bearing is making such a high pitched noise that you can't hear it.One other thing on older trans like a muncie you should have an older style gear lube in it the bearings and gears in older trans need the additives to help cushion them.
Last edited by sparky77; Mar 22, 2017 at 09:57 PM.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Check the dust cover on the front of the bellhousing. If it's close, when you push the clutch down that loads the thrust bearing to the front of the car. IF that dust shield is really close it could be the source of the noise. New, the crank should have .005 to .007 end play and that will grow as mileage goes up.
Drifting
Joined: Nov 2002
Posts: 1,787
Likes: 261
From: Blue Bell PA
2018 C3 of Year Finalist
Check the dust cover on the front of the bellhousing. If it's close, when you push the clutch down that loads the thrust bearing to the front of the car. IF that dust shield is really close it could be the source of the noise. New, the crank should have .005 to .007 end play and that will grow as mileage goes up.
It's most likely the throw out bearing .
Is my vette stock?? HAHA
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The throw out bearing will engage as soon as you put pressure on the clutch pedal, so of it makes noise as soon as you touch it, it's the throw out bearing, if it's making noise when you go all the way to the floor it could be a bad finger on the clutch itself. What does the noise sound like. Is it high or low pitched, is it a whir type sound or a grind? You could put it on blocks or a lift and have someone step on the clutch while you listen with a stethoscope to housing. If it spins up as the pressure is applied it is the bearing. If it happens after a lot of pressure is applied and come on suddenly it's a bad finger. If it's louder on the case it could be the input shaft bearing but it coming and going would leave me to believe its more likely the clutch
Last edited by Rescue Rogers; Mar 23, 2017 at 10:25 AM.
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Intermediate
Joined: Mar 2017
Posts: 45
Likes: 2
From: Naperville IL
Let us know what you do and how it works. I noticed nearly this same thing on my 72 this past Saturday. I could only hear the sound when I would push the clutch pedal to the floor while the car was rolling and in neutral. Not while sitting at a stop. Mine may be in such an early stage of going bad that it does not do it when the car is stationary. Good Luck!
Thread Starter
Team Owner
Joined: Jun 2001
Posts: 23,375
Likes: 1,067
From: Virginia USA
Will do. I just bought a cheap-o borescope that connects to my cell phone and it I get the time this weekend I'll see what I see. It seems it doesn't happen all the time. I did notice my clutch fork seems looser than it was when I installed it. Maybe one of the clips broke or something.