Trying to dispell myths about throw out bearing noises
10-11-2014, 05:47 AM
#1
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Trying to dispell myths about throw out bearing noises
I'm posting this in this forum because it seems like there are a few people who would be technically versed enough to discuss or understand what I'm saying:
I posted this in the transmission section as well...so if mods decide that one thread needs to go...please delete this one.
If not....then read below...and I appreciate any replies. Just be sure you can provide a reason for what you're saying/claiming.
If you want to reply to the original thread:
https://honda-tech.com/transmission-...rings-3225658/
I posted this in the transmission section as well...so if mods decide that one thread needs to go...please delete this one.
If not....then read below...and I appreciate any replies. Just be sure you can provide a reason for what you're saying/claiming.
I see a lot of what I believe is misconception about throw out bearings only spinning/contacting the clutch diaphragm when the pedal is pushed down.
The application is virtually any hydraulic Honda/Acura clutch system.
Can anyone explain to me what prevents the bearing from constantly contacting?
I'm looking for an answer from someone technically versed enough to explain themselves.
My reasoning for believing the bearing is a constant running type:
The slave cylinder has a spring in it. It constantly preloads the bearing against the fingers. Anyone that has taken a slave cylinder off/installed one can attest to this. The spring behind the slave cylinder piston expands till the bearing contacts the fingers. It's not much force...certainly not enough to depress the diaphragm spring. But the bearing always touches the fingers for this reason.
Freeplay is set at the MC. Its basically a measure of how far the pushrod sits from hydraulically activating the piston. Hydraulically preloading the system will cause the clutch to slip and the manual warns against that. I understand this. But that doesn't affect the slave cylinder mechanical spring that is always pushing on the bearing.
Am I wrong?
Thanks for the replies in advance!
The application is virtually any hydraulic Honda/Acura clutch system.
Can anyone explain to me what prevents the bearing from constantly contacting?
I'm looking for an answer from someone technically versed enough to explain themselves.
My reasoning for believing the bearing is a constant running type:
The slave cylinder has a spring in it. It constantly preloads the bearing against the fingers. Anyone that has taken a slave cylinder off/installed one can attest to this. The spring behind the slave cylinder piston expands till the bearing contacts the fingers. It's not much force...certainly not enough to depress the diaphragm spring. But the bearing always touches the fingers for this reason.
Freeplay is set at the MC. Its basically a measure of how far the pushrod sits from hydraulically activating the piston. Hydraulically preloading the system will cause the clutch to slip and the manual warns against that. I understand this. But that doesn't affect the slave cylinder mechanical spring that is always pushing on the bearing.
Am I wrong?
Thanks for the replies in advance!
If you want to reply to the original thread:
https://honda-tech.com/transmission-...rings-3225658/
10-11-2014, 05:47 AM
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Re: Trying to dispell myths about throw out bearing noises
On all the Honda clutch jobs I've done, if the slave cylinder is removed from the trans and left to its own devices, it will expand fully out.
I am confident that the bearing has to contact the diaphragm during operation.
I would say this is evidenced by the fact that when everything is assembled and the freeplay is set correctly....the fork is clearly already loaded into a postion...meaning you can't push toward the diaphragm any further. And if you push it toward the slave cyl and compress the piston...it just springs back into position til it stops when the bearing touches the fingers.
I'm basically trying to dispell myths about noises in the trans. I think that since the TOB is rotating or contacting the diaphragm at all times, a constant noise with the pedal in the up-position could very well be a TOB.
I've seen noisy TOB's in person...and nobody else seems to think that they can exist without pedal pressure lol.
I want to establish that is is a constant running bearing (some aftermarket sites have this info....Honda doesn't say whether it is or isn't). And then pose the question:
Why couldn't a noise with the pedal released be a TOB issue? Not saying it always is. But....why rule it out completely?
10-11-2014, 06:08 PM
#3
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Re: Trying to dispell myths about throw out bearing noises
But the blades on the pressure plate are always making contact on the TOB. If the TOB wasn't a bearing you'd be hearing alot of scraping noises. I know it comes grease so why are there issues with a TOB going out?
10-11-2014, 06:31 PM
#4
Re: Trying to dispell myths about throw out bearing noises
When your foot is off the clutch pedal, the throwout bearing is spinning, but there is no lateral force on it. Essentially, it's not bearing any kind of load. It also needs to ride on the pressure plate, otherwise when you engaged and disengaged the clutch, it would be changing speeds (similar to the gears in a transmission). Because it isn't lubricated in any way at that contact point, you would end up wearing the TOB out quickly, and possibly ruining pressure plates and sending little bits and pieces of pressure plate into your clutch. Not good. The pressure plate is fully closed (at least, it should be, if it's adjusted and installed correctly) so the TOB just "rides" on it. No load = no noise, unless it's ROYALLY fucked.
When your foot is on the clutch pedal, the throwout bearing is being pressed into the pressure plate. This puts lateral force on the bearing, making it carry a load. Standard bearings (like a TOB is) are not made to handle lateral forces - that's what cone bearings are for. Trying to fit one and make it work with a clutch system, however, would require a complete redesign, and no company wants to deal with that. They also have their own downsides, but we can leave that alone, since it doesn't apply. When you apply a lateral force to a standard bearing, it pushes the ***** into the races, causing wear. When your throwout bearing is worn out, that means the races and/or ***** are worn out. With your foot off the clutch, yes, they spin, but they aren't being shoved against each other. When your foot is on the clutch, those worn parts are being crammed against each other with a LOT of force, thus, it makes noise.
#MechanicalEngineering
When your foot is on the clutch pedal, the throwout bearing is being pressed into the pressure plate. This puts lateral force on the bearing, making it carry a load. Standard bearings (like a TOB is) are not made to handle lateral forces - that's what cone bearings are for. Trying to fit one and make it work with a clutch system, however, would require a complete redesign, and no company wants to deal with that. They also have their own downsides, but we can leave that alone, since it doesn't apply. When you apply a lateral force to a standard bearing, it pushes the ***** into the races, causing wear. When your throwout bearing is worn out, that means the races and/or ***** are worn out. With your foot off the clutch, yes, they spin, but they aren't being shoved against each other. When your foot is on the clutch, those worn parts are being crammed against each other with a LOT of force, thus, it makes noise.
#MechanicalEngineering
10-11-2014, 06:59 PM
#5
Re: Trying to dispell myths about throw out bearing noises
In terms of diagnosis, the same still would generally hold true - noise with pedal depressed = TOB (or PB) versus noise pedal up = transmission main bearing - because if a TOB is so screwed it makes noise with the pedal up, the noise will likely to be even louder with the pedal depressed.
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10-12-2014, 12:33 AM
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Re: Trying to dispell myths about throw out bearing noises
I think even an axially unloaded bearing running at 800RPM is liable to make some noise if there's something wrong with it or not.
TOB's develop play over time. Sometimes you hear a whirring or...scratchy type of bearing noise at idle.
Its the same noise that an OLD TOB makes when you take it out of the trans and spin it.
If you put pressure on it, it may quiten down because you're taking the "rattle" out of it by squeezing it.
Doesn't mean the bearing is bad. Just means its wearing and/or making a normal amount of noise for what its doing. You'd be chasing ghosts trying to fix normal noises.
I have, however personally changed out TOB's to eliminate whirring or rhythmic chriping noises that occurred with the clutch pedal in the UP position.
TOB's develop play over time. Sometimes you hear a whirring or...scratchy type of bearing noise at idle.
Its the same noise that an OLD TOB makes when you take it out of the trans and spin it.
If you put pressure on it, it may quiten down because you're taking the "rattle" out of it by squeezing it.
Doesn't mean the bearing is bad. Just means its wearing and/or making a normal amount of noise for what its doing. You'd be chasing ghosts trying to fix normal noises.
I have, however personally changed out TOB's to eliminate whirring or rhythmic chriping noises that occurred with the clutch pedal in the UP position.
10-12-2014, 09:08 AM
#10
Re: Trying to dispell myths about throw out bearing noises
With the help of a buddy, use an engine stethoscope to pinpoint the noise to the transmission versus clutch housing. Report back.
10-13-2014, 02:12 PM
#13
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Re: Trying to dispell myths about throw out bearing noises
Yeah my tranny was shipped from Maylasia, it does spin freely and it shifts fine when I stuck a screw driver through it and moved it around, didn't move it around like a mad idiot. Oh well we'll see. I went to the junkyard on Sunday and collect more parts. I'm going to run the clutch switches to start the car and for the cruise control. I want it close to stock as possible.
10-13-2014, 08:12 PM
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Re: Trying to dispell myths about throw out bearing noises
Incase you guys want to witness a colorful individual who says I'm totally wrong about the throw out bearing constantly contacting:
https://honda-tech.com/transmission-drivetrain-127/honda-constantly-engaged-throw-out-bearings-3225658/
:facepalm:
https://honda-tech.com/transmission-drivetrain-127/honda-constantly-engaged-throw-out-bearings-3225658/
:facepalm:
10-13-2014, 08:19 PM
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Re: Trying to dispell myths about throw out bearing noises
Incase you guys want to witness a colorful individual who says I'm totally wrong about the throw out bearing constantly contacting:
https://honda-tech.com/transmission-...rings-3225658/
:facepalm:
https://honda-tech.com/transmission-...rings-3225658/
:facepalm:
10-14-2014, 04:00 AM
#16
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Re: Trying to dispell myths about throw out bearing noises
I'm not so sure he's trolling. He started this "discussion" with me in the Prelude forum. "Discussion" meaning every time i asked him to explain how he thinks clutches work...he just started swearing and typing nonsense. I think he actually believes what he's saying makes sense. If anyone else can make sense of it...please let me know.
10-14-2014, 05:40 AM
#17
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Re: Trying to dispell myths about throw out bearing noises
Pedal play does need to be set in order to do a proper bleed, but that has nothing to do with the cmc and smc because the pedal play isn't that "secured" onto the cmc. If you notice the pedal is still kind of loose by putting your foot under the pedal and lifting it a little.
Even before bleeding the clutch pedal the TOB is already physically touching the pressure plate.
Even before bleeding the clutch pedal the TOB is already physically touching the pressure plate.
10-14-2014, 04:28 PM
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Re: Trying to dispell myths about throw out bearing noises
The ISB and the TOB are both unloaded and spinning the same speed at idle in neutral (clutch engaged).
So...why can the ISB make noise but the TOB cant? They're both operating under the same conditions. No?
So...why can the ISB make noise but the TOB cant? They're both operating under the same conditions. No?
10-14-2014, 05:10 PM
#19
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Whoaaaa... All the big posters here in one thread, discussing stuff I wish I'd been taught? This is the best debate I've ever seen on here. I also wish my manual trans professor was this descriptive last semester, then I might've actually learned more than what I already knew...
10-14-2014, 11:41 PM
#21
Re: Trying to dispell myths about throw out bearing noises
I already covered why they make noises in different conditions in my last post in this thread. Long story short, both bearings do completely different jobs, and thus fail in different ways. The ISB keeps the shaft spinning freely in place - after so many millions of revolutions, the cage gives out, the bearings start smacking the **** out of each other, and they break down, causing an ISB noise. The TOB spins with the pressure plate, so that it can properly press the springs down without wearing a hole in them. When it fails, it fails laterally, damaging the races before the *****, and only causing noise when it's under those same lateral forces.
10-15-2014, 01:10 AM
#22
Re: Trying to dispell myths about throw out bearing noises
I believe they both can make noise. The weird or hard part to explain would be why the TOB would make noise unloaded and spinning but stop making noise once loaded. I guess the same phenomena would be hard to explain on the ISB too. But I suspect the ISB, once it starts being noisy, never stops being noisy due to wear and loss of the tight tolerances.
Then again, I've never seen a TOB ripped apart, how tight are the bearings in the races on a TOB. I know the ISB, Pilot and every other bearing in the tranny I looked at has zero play whatsoever. The bearings and races are somehow magically merged together with zero play. At least that's the impression I got when inspecting them. I am fascinated by the tight tolerances and would love to see how one of those bearings is assembled. I don't even think using the trick of heat expansion on the outer race and cold contraction on the inner race and ball bearings would let it slide together.
Anyways, the TOB didn't seem to be of that same exacting tolerance and I believe it could vibrate when not loaded but spinning, then load makes it seat into the races and quiet down. That's the theory I got running through my head for it.
Then again, I've never seen a TOB ripped apart, how tight are the bearings in the races on a TOB. I know the ISB, Pilot and every other bearing in the tranny I looked at has zero play whatsoever. The bearings and races are somehow magically merged together with zero play. At least that's the impression I got when inspecting them. I am fascinated by the tight tolerances and would love to see how one of those bearings is assembled. I don't even think using the trick of heat expansion on the outer race and cold contraction on the inner race and ball bearings would let it slide together.
Anyways, the TOB didn't seem to be of that same exacting tolerance and I believe it could vibrate when not loaded but spinning, then load makes it seat into the races and quiet down. That's the theory I got running through my head for it.
1: Backing plate with the fork engagement fingers
2: a wavy thrust/load/offset(whatever you wish to call it) washer/spring - example link
3: Open (as in not fully sealed) bearing races and bearings (I forget which kind of bearing, and i didnt take pics...dammit) (also contains the Load Ring, the bit that contacts the diaphragm)
4: Outer housing held in place by simple crimped steel fingers.
Now, I believe that I may have my original TOB floating around in a parts box, and I can tear it apart tomorrow if anyone is interested enough to desire pics. The fun part is...I had a rear main leak that oil-contaminated my TOB...I ended up replacing the seal and cleaning everything up...and then I decided to attempt to rebuild my TOB, so i took it apart carefully ( bent back the two metal fingers) it unloaded the bearing by nearly a quarter inch (spring loaded remember), then i cleaned all of it out entirely with brake cleaner, which of course stripped the bearings dry...so i repacked it with the Honda-brand High Temp Urea Grease using the same procedure youd use on any serviceable bearing assembly, reassembled the TOB under load, and bent the fingers back into position and stamped the fingers down for load retention...thus a cleaned and repacked 2 month old TOB. I've run it now for just over 7 months...still makes the same very slight noise (clutch pedal up) it did brand new. So, yeah, I'm cheap...but I thought it might be a somewhat interesting experiment. So far, so good.
Quick version: the bearing races in the TOB housing are under load, the rotational mass of the bearing is under no static load on its own. This refers to a TOB that isnt installed.
Last edited by MisereNoire; 10-15-2014 at 03:53 AM. Reason: Fixed inaccuracies
10-15-2014, 03:26 AM
#23
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Re: Trying to dispell myths about throw out bearing noises
So now he's listing websites and is trying to prove his point, but in return it also proved my point, or everyone else in THIS section of the forum as well
10-15-2014, 03:42 AM
#24
Re: Trying to dispell myths about throw out bearing noises
Well, to be honest...the last few posts stated that theyd not seen a TOB apart, and I figured it wouldnt hurt to have it described with a couple of examples i could find. Not really making a point, just providing info.
10-15-2014, 04:24 AM
#25