throw out bearing going bad?
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Team Owner
Joined: Apr 2001
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From: Dallas TX
throw out bearing going bad?
How can you tell if a throw out bearing is going bad? I thought it was normal for the tranny to make noise when the clutch engages in neutral ... but someone that listened to is said it's louder than usual for a stock flywheel/clutch.
Le Mans Master
Joined: Apr 2001
Posts: 7,411
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From: Little Elm TX
Re: throw out bearing going bad? (GlockLT4)
Well mines not stock now, so it makes all kinds of noise with it in neutral with the clutch out. :eek: When it was stock the tranny didn't make any gear noise with the clutch out and it in neutral. Now I've heard there is some differences between the years on the 6spds so that might account for some of the noise. Maybe someone else with a stock '96 gearbox can give you some more info?
Melting Slicks
Joined: Jul 2001
Posts: 2,526
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From: Warrick County IN
CI 3-4-5-6-7-8-9-10 Veteran
Re: throw out bearing going bad? (GlockLT4)
Curtis how much noise and what type does it make? Is it like a low rumbling? The guy before me had just gotten the clutch, throw out bearing, and flywheel replaced by the dealer under warranty. The only time mine makes any noise is idling in neutral during normal shifts or with the clutch depressed there is no noise. I think the six speeds have a little gear noise in neutral with the clutch out anyway? Mine makes a little noise not a whine or anything like that but just like a set of gears rolling over.
Racer
Joined: Sep 1999
Posts: 433
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From: Durham NC
Re: throw out bearing going bad? (GlockLT4)
My understanding is that with the pedel out (clutch not engaged) the ZF will clunk at idle speed. Mine does that. When you depress the pedel and engage the clutch the clunk disappears.
Le Mans Master
Joined: Jun 2002
Posts: 6,097
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From: Cincinnati Oh
Re: throw out bearing going bad? (GlockLT4)
I thought it was normal for the tranny to make noise when the clutch engages in neutral .
Others say its 'normal' for the ZF to make noise with the clutch disengaged (like mine does), however, the ZF site says its a bad input bearing when this occurs. Check out the ZF site to determine exactly what's up, lots of good info there. Good Luck.
Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
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From: Dallas TX
Re: throw out bearing going bad? (GlockLT4)
Here's something I found on zfdoc.com's FAQ page:
(Q.) Bill, I own a 1990 Corvette with the 6 speed ZF. I have a transmission noise which many other Corvette & Camaro owners report as "normal". This noise is most prominent in neutral & 1st gear and is commonly described as the "rocks in a can" sound. Two local companies that rebuild (only) Muncie & Borg-Warner 4 speeds have heard this description and believe it to be the front bearing and possibly one of the ball bearings rolling around inside the trans case. From your experience is this "really" the problem which many people report hearing only in THIS model trans? Duane Barcena of north Chicago.
A.) Duane, it would be a nearly impossible for a ball bearing to fall out of the main bearing case. If the noise goes away when you push the clutch in at idle,... that could be 1 of 3 things, either a bad dual-mass flywheel, or the flywheel is not an original dual-mass type but instead is a single mass type. The ladder situation will produce a sound known as gear clatter while in neutral which is harmless to the transmission. The springs in the clutch disc, which are not present in the disc of a dual-mass set up, will oftentimes produce a rattle like resonance in the 1K - 2K RPM range when under moderate to heavy power load settings. These are the drawbacks of converting over to a single-mass flywheel.
A bad input bearing in the transmission will normally produce a whirling or whining sound proportional in pitch to engine revs. In 1st gear the whine is most prominent decreasing in intensity in each subsequent gear to the quietest level being 4th gear (direct drive energy flow).
A bad dual-mass flywheel with a failing damper will sound like a diesel truck engine at idle or a clacking noise. Under certain load settings, this sound may be heard occasionally in 1st gear too.
The main bearings in a ZF S6-40 are very different from those used in Muncie & Borg-Warner 4 speeds. The ZF main bearings are self-contained non-preload non-tapered double-row type bearings. One row is comprised of cylindrical type bearings and the other row is comprised of ball type bearings. This type of bearing would be more similar to the type of bearings used in turbine engines.
If it sounds like a diesel engine at idle, the flywheel dual mass damper may be failing. What I've seen happen before is that when a flywheel is determined to be bad, some people choose to replace it with a less expensive single mass type flywheel where they can buy the flywheel, pressure plate with throw-out bearing and clutch disc for $800 instead of $750 for OEM flywheel and $300 for the clutch kit.
If it is more of a whining or whirling sound, the input bearing has been compromised. This results from the alignment of the transmission during reinstallation is off slightly where the trans, bell housing butt up to the block. I've never heard of a ZF S6-40 main bearing going bad on it's own. FYI, I've rebuilt 125 of these units and have at least 7K hours of experience with the ZF S6-40 design.
Sounds to me like the throw out bearing is wearing... i have some gear whine in first and it goes away more the higher the gear i'm in on top of the whir noise when in netural with the clutch engaged.
(Q.) Bill, I own a 1990 Corvette with the 6 speed ZF. I have a transmission noise which many other Corvette & Camaro owners report as "normal". This noise is most prominent in neutral & 1st gear and is commonly described as the "rocks in a can" sound. Two local companies that rebuild (only) Muncie & Borg-Warner 4 speeds have heard this description and believe it to be the front bearing and possibly one of the ball bearings rolling around inside the trans case. From your experience is this "really" the problem which many people report hearing only in THIS model trans? Duane Barcena of north Chicago.
A.) Duane, it would be a nearly impossible for a ball bearing to fall out of the main bearing case. If the noise goes away when you push the clutch in at idle,... that could be 1 of 3 things, either a bad dual-mass flywheel, or the flywheel is not an original dual-mass type but instead is a single mass type. The ladder situation will produce a sound known as gear clatter while in neutral which is harmless to the transmission. The springs in the clutch disc, which are not present in the disc of a dual-mass set up, will oftentimes produce a rattle like resonance in the 1K - 2K RPM range when under moderate to heavy power load settings. These are the drawbacks of converting over to a single-mass flywheel.
A bad input bearing in the transmission will normally produce a whirling or whining sound proportional in pitch to engine revs. In 1st gear the whine is most prominent decreasing in intensity in each subsequent gear to the quietest level being 4th gear (direct drive energy flow).
A bad dual-mass flywheel with a failing damper will sound like a diesel truck engine at idle or a clacking noise. Under certain load settings, this sound may be heard occasionally in 1st gear too.
The main bearings in a ZF S6-40 are very different from those used in Muncie & Borg-Warner 4 speeds. The ZF main bearings are self-contained non-preload non-tapered double-row type bearings. One row is comprised of cylindrical type bearings and the other row is comprised of ball type bearings. This type of bearing would be more similar to the type of bearings used in turbine engines.
If it sounds like a diesel engine at idle, the flywheel dual mass damper may be failing. What I've seen happen before is that when a flywheel is determined to be bad, some people choose to replace it with a less expensive single mass type flywheel where they can buy the flywheel, pressure plate with throw-out bearing and clutch disc for $800 instead of $750 for OEM flywheel and $300 for the clutch kit.
If it is more of a whining or whirling sound, the input bearing has been compromised. This results from the alignment of the transmission during reinstallation is off slightly where the trans, bell housing butt up to the block. I've never heard of a ZF S6-40 main bearing going bad on it's own. FYI, I've rebuilt 125 of these units and have at least 7K hours of experience with the ZF S6-40 design.
Sounds to me like the throw out bearing is wearing... i have some gear whine in first and it goes away more the higher the gear i'm in on top of the whir noise when in netural with the clutch engaged.
Race Director
Joined: Sep 2001
Posts: 14,680
Likes: 752
From: NEwhere Ohio
Re: throw out bearing going bad? (GlockLT4)
C4's with the ZF transmission (Even with the stock dual mass flywheel) make knocking-like noises at idle with the clutch engaged (pedal up (released)) and with the transmission in neutral..mine is like this too even with a new clutch and Throwout bearing (of course I went with the lightweight flywheel which didnt add any extra noise in neutral w/ clutch engaged as you are describing, but did add noise while going uphills under load in too high of a gear..)..dont let anyone trick you into thinking somethings wrong with yours. ZF is a noisy transmission...end of story
