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Have an all stock 2010 ZR1 with 18k miles that I feel pedal pressure to be much greater than normal. Owned a 2005 C6 with an aftermarket clutch that was comparably heavy in pressure maybe slightly less. On that car I replaced master cylinder after 9 years of owning it when pressure increased and engagement point changed in location and amount of travel in friction zone.
Clutch friction zone feels great and pedal travel is linear in amount of pressure. I have swapped out clutch fluid via ranger method and it was dirty but nothing I haven't seen before on my 2005.
I know Zr1 clutch is different in the fact that it doesn't adjust self adjust and that as the clutch wears that the pedal pressure is going to increase. Original owner told me that it was heavy the day she bought it new. Though I know something is amiss as I have test driven a 2010 Zr with 12k miles where the clutch pedal was just as light as my brother and dads 2008 base models.
Only other info is when driving enthiastically on highway after shifting. Pedal would feel very light in the top half of pedal travel and spongy at bottom.
Planning on replacing master cylinder and wanted to see if anyone had any advice on what might be culprit. Blockage in fluid going to slave? Just a worn out clutch? Order of things to replace? What is mechanical reason for Zr1 clutch getting heavier as it wears? And if pedal was this heavy when new what could be a reason for it to be heavy brand new? Bad spring somewhere?
Other than amount of pressure to push pedal in the clutch feels great! No chatter or vibrations. No odd sounds or clicking. Ideas? Thanks
On the OEM LS clutches, all the Slave cylinders have a spring behind the threw out bearing (under the green boot), so as the clutch wears, the slaves throw out bearing will self adjust to the clutch pressure plate spring fingers to maintain a zero gap.
Seal part of the slave, since you can't see it in the above photo to get a full sense of all the parts of the slave cylinder.
Now on a standard LS-7 clutch (currently replacements for the LS2, ls3, ls7), it has a flywheel plate, a single disco, then the pressure plate.
So the flywheel surface one side, the pressure plate surface on the other side, and both side surfaces of the single disc to those two surfaces as your lock up areas.
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On a LS9 clutch, you have two extra parts, being a second disc, and an additional steel plate that goes between the two discs. So now you have 4 pads surface, and 4 steel surfaces that the two discs will contact against.
So, you have this,
And inside the pressure plate housing is the second disc and the added contact plate.
So when you push the pedal in, the Throw out being pushed against the spring fingers, but instead of just releasing the pressure from a single disco, it now releasing the pressure from the two discs and center plate as well.
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Knowing this, now we dive into your problem.
Since you have two discs that are riding on the torque tube shaft spines, if there is a build up of either clutch dust between the disco center spines and the shaft spines, or the shaft spine is rusted to hell, your going to feel the added pressure of the discs trying to move on the shafts as your pressing in the clutch. Same goes for burs on the splines that can cause the same problem. To take this one forward, the center of the torque tube shaft is riding in a pilot being in the center of the flywheel to keep it straight, and if the pilot bearing goes out, it can cause problems with the shaft not staying centers as the TB is applying pressure, with more pedal pressure needed as well.
To throw a monkey wrench into the works too, on the clutch peddle, there is an assist spring. Being that once you get the pedal about half way down, the spring lessens the tension need to push the pedal from that point to the floor. When the pedal gets about half way back up, the spring tension changes directions, and now puts tension to pull the al the way back isntead.
So step one for free fixes to try, get the car up on a lift, and using compressed air in the Bell housing port, blow the clutch dust out of the bell housing to get as much of the clutch dust you can out of the housing and clutch.
The C6 bell housing has 3 ports, so you first start the blow out cleaning (wear a tyvek hoody suit and respirator since it going to be dusty), then put someone in the car during the last blow out to work the clutch pedal so you can blow out as much of the dust in the pressure plate assembly as well.
Next, double check the pedal to make sure that assist spring has not been removed or snapped one of legs off.
Also, make sure that you have done the ranger fluid change, with clean fluid in the system.
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Now if the above did not help the problem (LS7 clutch and LS9 clutch take about the same pedal pressure to work the clutch), then it time to pull the clutch to check the system.
Since you have good lock up, can bank that the pressure plates, the disco are fine, and really just focusing on the TB sleeve to make sure it not melted, the clutch fingers to make sure they are not going out/bent and the pressure plate assembly clean of dust, the end of shaft and pilot bearing still good, then a lot of focus on the Torque tube shaft bearing, the shaft spines, and the Disc's spines as well.
Hence with the OEM clutch always been heavy from the start, and with little mileage on the car, would dare to guess that the problem has always been a problem with the shaft to disc spines, and what needs to be cleaned up to solve the problem.
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P.S, Pray like hell you don't run into this problem once you get everything apart.
Hence first off the pilot bearing in the fly wheel went south (look at the end of the shaft), so out the gate, going to need a new torque tube shaft and pilot bearing.
Next, we have the throw out bearing race sleeve that melted, ending up with the TB bearing melting down on the race support sleeve.
Top left one,
So not only will you need a new slave cylinder due to the above, but with the amount of plastic that was sprayed to the clutch assembly to melt into it works, pretty much need a new clutch too.
Wow. Thanks for the detailed explanation! Is it possible to rule out any of the possible problems i.e.: if pilot or throw out bearing was bad there would be odd sounds/chatter or sounds from clutch when car is just idling?
Gonna try to explain to my mechanic about the 3 ports on the bell housing and see what they can do. How does the clutch dust from inside bell housing get into hydrolics?
Based on what I was feeling after high rpm shifts. Kinda like the peddle wanted to stay low but the dual action spring was keeping it up. A sticking to the floor pedal usually indicates a bad master cylinder?
This car was garaged its whole life and only driven in sunny weather. Wouldn't that make it less likely something internal is rusted?
So because Zr1 clutch doesn't self adjust as it wears. That is because the slave cylinder doesn't have a spring on throw out bearing?
Hence with the OEM clutch always been heavy from the start, and with little mileage on the car, would dare to guess that the problem has always been a problem with the shaft to disc spines, and what needs to be cleaned up to solve the problem.
Shaft to disc spline problem would just require a new clutch? Part 24260226?
Think I found answer to how it gets into clutch hydrolics.
As you USE the clutch you consume it and where does the debris go? As the clutch material is flung around within the bell housing the material gets past a seal into the slave cylinder and then the hydraulic system the fluid is contaminated and begins to darken. If allowed to worsen you eventually will have a sticking pedal and lose hydraulics. In most cases not permanent but often at the most inopportune times. It is best to address this as early as possible so you do not have permanent issues with the stock slave.
So because Zr1 clutch doesn't self adjust as it wears. That is because the slave cylinder doesn't have a spring on throw out bearing?
Again, the pressure plate has pressure on all the discs/bearing surfaces, so as any of them wear, the pressure in the pressure plate adjusts for this. And again, there is a spring behind the Throw out bearing in the slave too.
So spring in the slave keeps the TB against the clutch fingers to self adjust to the pressure plate fingers as the pressure plate is self adjusting for wear of the plates and disc as well.
Simply, both the clutch and the slave are self adjusting for the life of the clutch.
As for torque tube shaft spines, and even clutch disc spines, 99% of the time, all that is need to clean up the spines is a file and some sandpaper.
The only time I call the torque tube input shaft cooked, is when it's either bent, spines can not be cleaned up, or the end area that is going to ride inside the pivot bearing worn to hell instead.
Hence the spines are worn so much on this torque tube input shaft (single plate clutch system and you can see where the disco moves front to back on the shaft spines that it worn out the spines in that area) that I would never reuse the shaft.
part #25
As for rust on the torque tube input shaft, could be, but its not hard to clean up once you have the shaft in hand. Hence once cleaned up, you first use the free disco on the spines to make sure that they move freely against each other, and then since the second disc is captured in the pressure plate, you use the entire pressure plate to make sure that caputured disc in it is moving freely on the shaft spines as well.
The fact that the clutch has been hard from the start, is screaming a binding problem between the shaft spines and the disc spines instead. Hence as you push in on the clutch pedal (TB pushed into the spring fingers), this releases the pressure on the pressure plate, and the discs have to be able to move on the spines to disengage from the fiction surfaces (4 of them on the dual clutch).
So between the clutch system hydraulics and the pedal assists spring, you have plenty of pressure to make pushing the pressure plate springs in with ease, so this brings the problem back to the discs not moving freely on the spines instead. So could be dust build up, could be rust build up, or since problem has been from the start, problem with discs not being able to move cleanly on the shaft spines to start with.
Skip to 00: 45, and keep in mind that you have 2 discs that have to move freely on the shaft spines on a LS9 dual disc clutch as the pressure plate release and reapplies pressure.
As for clutch dust in the fluid, that one is easy to explain.
What is missing on the slave seal, is front V shape swipers that will push the clutch dust on the slave bearing surfaces forward with the seal( being pushed forward as the fluid moves the seal forward as you push the pedal in). Since the front side of the seal is rounded as you see above, then the seal just runs over the clutch dust on the bearing surfaces of the slave, trapping the dust in with the fluid behind the seal isntead. Look below the seal and that black you see on the metal is clutch dust that the seal has just been pushed over as it was driving forward.
Hence even with ports on the bell housing, the inside off the bell housing is far from being a clean area that is shows in the above photos, and but in fact just littered with clutch dust on every surface instead.
Quote:
"The clutch system on the ZR1 uses a new dual disk system which is significantly different than the regular Corvette Z06. The regular clutch has a self-adjusting feature that allows the pedal effort to be consistent throughout the life of the clutch. The ZR1 clutch will not self-adjust and the pedal effort will increase as the clutch wears. The pedal effort is higher on a ZR1 and will get progressively higher as the clutch wears."
Heading to my tranny guy to see what he says. Just for clarity this is what I read about the zr1 and how it compensates for clutch wear.
At 12k miles,the clutch is just now starting to mate in correctly if used correctly (should last well over 80k even with aggressive driving), and if it's anywhere near worn out, someone had to have abused the hell out of the clutch by over slipping it at launches instead.
Hence a lot of these with just smoking the clutch by over slipping it, isntead of the it fully locking up fires, to spinning the tires afterwards. So not bye-bye $600 tires, but bye-bye $3K clutch that he smoked instead.
Truth is, would let someone else get behind the wheel that has driven a ZR1, since I don't notice the pedal being stiffer between it and a Base model clutch instead. If it's is as bad as you say it is, then sounds like it time to pull it apart, and get to the bottom of the problem.
The glitch , its a $1K labor bill for some shop to get that deep into the clutch to begin with, and by the time you get that deep into the parts pull, best to just replace the clutch and needed parts as well. So that brings the bill up to the $3K mark real fast isntead.
As for dropping another OEM LS9 clutch back in if needed (someone did toast the clutch), up to you, but there are a lot better clutches over the OEM unit instead. Hence the OEM clutch is designed to slip if you over power it at launch, so it saves the drive line isntead (GM warrantied the drive-line, not the clutches, so you can see which way the went with a weak link).
If your looking for a better clutch to drop in while you have it all apart and need a new clutch, then ECS has the Mantic 9000 with increased tension pressure plates that may suit the bill instead.
Ordered new OEM clutch. Like you said. Might as well replace it after opening it all up. Now gotta wait for parts!!
-Ed
Would wait on ordering parts until you get the car apart; unless you can return parts without being hit with a restocking fee if they are not used.
Hence if you want to have parts on hand just in case, then your talking new flywheel with pilot bearing, new flywheel bolts, new clutch bolts, new clutch, new slave cylinder, new torque tube input shaft and maybe even parts in the torque tube for the shaft connections and it bearing.
Also to point out, the ECS Mantic 9000 clutch kit with increased tension pressure plate is more expensive, but is light years better than the stock clutch. With that kit, you just need to make sure that you add the pilot bearing to the kit, but may still need to pick up a new torque tube input shaft if your is toasted.
Note, double check with ECS to see if the below kit has the standard tension pressure plate, or has the increased tension plate. Hence you want the increased tension pressure plate, since in not only adds holding power of the clutch, but makes sure that the clutch reengages quickly at high RPM shifts too. http://www.eastcoastsupercharging.co...tegory_id=1369
As for the new master clutch cylinder, don't swap that unless you have a extra hundred laying out to burn, since if you have problems with the old master cylinder, GM will replace that for free while upgrading it to the new style master cylinder instead.
Also, on the slave cylinder either way (reusing the old one, or just replacing it with a new one), replace the plastic Throw out bearing support to a metal one; Even if the old slave unit plastic support is still good and going to reused the old slave.
As for one last thing while you are deep into the clutch, then would be the time to add in a remote bleeder line.
The ranger method works well to keep the fluid clean, but with the katech bleeder in place. ,makes powder bleeding the clutch fluid a snap, with all the clutch dust out at the same time as power bleeding.
Note, get this Katch remote bleeder if your going to add in a remote bleeder, since the Katch bleeder has been proven to be trouble free; while others have been not the case isntead. http://store.katechengines.com/c6c7-...r-kit-p96.aspx
Ordered that metal bearing!! Hoping that he opens it up and says it just needs a cleaning. But while it's opened up might as well replace clutch. Since only symptom is heavy clutch I can't justify buying every part in there. Just gonna have to see what he says. If flywheel was damaged wouldn't I have different symptoms? Hoping to just replace/fix what's making clutch heavy without my wife knifing me in the back for spending too much. Haha
I think things got way too crazy way too fast here.
First of all, if that bearing support were melted you would be having issues like a leaking slave and noise when depressing the clutch.
The heavy pedal could honestly just be normal. The ZR1 has a higher clamping force than a base so naturally with near identical hydraulics, you will experience a heavier pedal.
The spongy feel after spirited driving is more than likely just some disgusting clutch fluid.
Purge the clutch fluid and replace it with a quality DOT 4 like RBF 600. Do not use DOT 3 or 5.
I would be willing to bet that if you opened the clutch fluid reservoir, you will find that the fluid is a putrid black/brown color.
Summary....
Don't get crazy. Flush the fluid thoroughly either through the bleeder or the ranger method multiple times. Likely there is no issue with the clutch itself.
Good luck.
I do agree that if you do replace things to use the billet bearing support. Smart. Just trying to save you some money. If the clutch randomly became heavy, I would be concerned. In this instance, you will probably get all the miles you want out of it.
At 12k miles,the clutch is just now starting to mate in correctly if used correctly (should last well over 80k even with aggressive driving), and if it's anywhere near worn out, someone had to have abused the hell out of the clutch by over slipping it at launches instead.
Hence a lot of these with just smoking the clutch by over slipping it, isntead of the it fully locking up fires, to spinning the tires afterwards. So not bye-bye $600 tires, but bye-bye $3K clutch that he smoked instead.
Truth is, would let someone else get behind the wheel that has driven a ZR1, since I don't notice the pedal being stiffer between it and a Base model clutch instead. If it's is as bad as you say it is, then sounds like it time to pull it apart, and get to the bottom of the problem.
The glitch , its a $1K labor bill for some shop to get that deep into the clutch to begin with, and by the time you get that deep into the parts pull, best to just replace the clutch and needed parts as well. So that brings the bill up to the $3K mark real fast isntead.
As for dropping another OEM LS9 clutch back in if needed (someone did toast the clutch), up to you, but there are a lot better clutches over the OEM unit instead. Hence the OEM clutch is designed to slip if you over power it at launch, so it saves the drive line isntead (GM warrantied the drive-line, not the clutches, so you can see which way the went with a weak link).
If your looking for a better clutch to drop in while you have it all apart and need a new clutch, then ECS has the Mantic 9000 with increased tension pressure plates that may suit the bill instead.
Update:
Had clutch master replaced and pedal feels much lighter. Still heavier then the other zr1 I drove but 50% lighter than before. Planning on getting transmission opened up to see what's going on. Planning on replacing fly wheel and slave with metal bushing. Is there a reason that the flywheel might not need to be swapped or just makes sense if you open it up to replace everything?
Update:
Had clutch master replaced and pedal feels much lighter. Still heavier then the other zr1 I drove but 50% lighter than before. Planning on getting transmission opened up to see what's going on. Planning on replacing fly wheel and slave with metal bushing. Is there a reason that the flywheel might not need to be swapped or just makes sense if you open it up to replace everything?
Just depends on the condition of the flywheel surface when you have it open. Hence if the clutch is about worn out, you can bank that the surface of the flywheel is on it latter days as well.
Update: Had new OEM clutch installed with flywheel and clutch slave. Wow. It's a new car. Peddle pressure is identical to my brother and fathers base 2008 Vettes. Will try and post some pictures of the flywheel and clutch. Flywheel was scorched in a few spots. Clutch was pretty worn. Makes me wish companies would use number to define pressure. Perhaps as a range like. For instance my guesses would be:
2010 zr1 clutch pressure when I bought it: 80lbs
2010 zr1 clutch pressure after swapping clutch fluid 10x: 80lbs
2010 zr1 clutch pressure after new master cylinder installed: 50lbs
2010 zr1 clutch pressure after new clutch: 8-10lbs. Super light.
When you go onto an aftermarket clutch companies website they just use words like soft.....heavy......If I could could have some assurance like this clutch is gonna increase your pressure to 15-20lbs. Easily better than the sensation of new tires!!!
Numbers obviously not exact but just to prove a point of amount of pressure. But for reference with new clutch it is identical in feel to 2008 base models in pressure.
P.S, Pray like hell you don't run into this problem once you get everything apart.
Hence first off the pilot bearing in the fly wheel went south (look at the end of the shaft), so out the gate, going to need a new torque tube shaft and pilot bearing.
Well, praying didn't help in my case... I sent my 08 base coupe to the shop with a strange noise that I suspected was a bad front torque tube bearing. Though the clutch was holding up fine, at 111,000 miles I figured a new clutch was in order. Short story, my clutch came out but the input shaft is destroyed at the pilot bearing (as above).
Anybody know the actual PN of the input shaft (item #25) in the diagram? Google is not helping me.
Note, search field is 2008 ZR1 for the above, so if you have a different year/model, then change that so it correct to begin with, then search under drive line/ shafts.
02-18-2018, 02:04 PM
ZR1 clutch pedal pressure
