intermittent grinding (all gears)
08-13-2005, 09:16 PM
#1
intermittent grinding (all gears) i installed a clutch 2 weeks ago,i revved the car up to about 4k, it was in 1st gear and i was sure the clutch pedal was all the way down. apparently it wasn't, i heard a faint grinding sound. i didnt think much of it, until when i got moving again and as i was shifting it started to sound like a moan or groan and if i continued to shift it would grind and eventually go into gear. then it just went away, shifting to 2nd and 3rd. i parked the car as soon i could. waited a few hours. then started driving again and everything seemed fine. no noise. then i attemped a downshift to 2nd gear and the moan and groan/grind came back. i bled the hydraulics 3 times since and the sound hasnt gone away. every test drive it happens but i dont know which gear or when its gonna happen. if i baby it, and pump the clutch 3 times before i shift the grinds/ or moans wont happen. i have no leaks in my lines, and pedal pressure is still firm the clutch is a spec stage 2. if anyone knows whats up and can help that would be great.
08-16-2005, 11:31 AM
#4
yes it shifts smoothly with the engine off or at very low rpms. we had it up on a lift the other day and anything under 1500 rpms it will shift through the gears fine. i am going to work on it again this weekend but im still lost as to what it could be.
08-16-2005, 04:04 PM
#5
Hmmm could possibly be a pressure plate issue. Some pressure plates can "bind up" at high RPM due to centrifgual force that pulls the fingers out excessively. This could be the "moaning" you're hearing. Did you torque in the correct pattern and to the proper spec? Did you also replace the flywheel when replacing the clutch? Have it resurfaced?
08-16-2005, 11:18 PM
#6
im beginning to think it might be the pressure plate or throwout bearing. the flywheel is a new gm unit. i did proper torque specs and a criss cross pattern. everything was fine for a good 300 miles, and then i revved it up. im thinking that during the revv if the pedal wasnt all the way too the floor then the only parts that were in contact were the pressure plate, throwout bearing, hydraulics, transmission. transmission is fine. shifts fine and since the problem was intermittent and, not one particular gear. i ruled out the tranny because it would be reoccuring if i screwed a syncro or gear up. hydraulics seem fine, firm and rebled the system 3 times thus far. this finally leads me to thinking its a bent/ cracked throwout, that when i pump the clutch it fully pushes the throwout against the pressure plate. if this isnt the case. then my pressure plate like you said got screwed up. if so, do you think that retorqueing it down will help me out, or am i gonna have to get a whole new pressure plate?
08-17-2005, 01:06 AM
#7
I am having somewhat the same situation... Same setup... Got the tranny built with upgraded syncros... steel shift forks... new gears... etc! Any and all help would be nice! Thanks in advance!
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08-17-2005, 01:53 PM
#8
If you're having to pump the clutch after a high RPM rev this indicates that the pressure plate diaphragm is expanding and pressing against the slave cylinder. This is forcing clutch fluid back into the master and positioning the slave further away from the diaphragm for the next clutch release. When you let off the RPMs you'll need to pump the clutch to get the slave closer to the diaphragm with each pump. The last "good" pump is the slave engaging the diaphragm.
The slave really only moves a small amount with each pump of the master (but with much more force), so the slave must sit very close to the pressure plate diaphragm to properly engage it with 1 pump of the clutch.
Here's the list of things I think it could be:
-Hydraulic system not completely bled. Air in the slave allowing the slave to retract too far. Also, double check that you've properly routed the hydraulic line with the protective rubber under the heat shield by the catalytic converter. don't leave any excessive line down there, it'll only be more surface area to heat up.
-Flywheel not fully or evenly seated. Check with dial indicator for runout.
-Bad pressure plate diaphragm or bent pressure plate. (LS1 pressure plates have a history of being weak and being a bad design anyway. There are a few TSBs out there dealing with the diaphragm not releasing at high RPM)
I would think if the plate is bent re-torqueing could potentially straighten it, but I wouldn't know of a sure way to determine if it was straightened. Either way I don't know how comfortable I'd be with a bent and re-bent 15+lb mass rotating at 6000 RPM right by my legs. The clutch you purchased didn't come with a pressure plate?
The slave really only moves a small amount with each pump of the master (but with much more force), so the slave must sit very close to the pressure plate diaphragm to properly engage it with 1 pump of the clutch.
Here's the list of things I think it could be:
-Hydraulic system not completely bled. Air in the slave allowing the slave to retract too far. Also, double check that you've properly routed the hydraulic line with the protective rubber under the heat shield by the catalytic converter. don't leave any excessive line down there, it'll only be more surface area to heat up.
-Flywheel not fully or evenly seated. Check with dial indicator for runout.
-Bad pressure plate diaphragm or bent pressure plate. (LS1 pressure plates have a history of being weak and being a bad design anyway. There are a few TSBs out there dealing with the diaphragm not releasing at high RPM)
I would think if the plate is bent re-torqueing could potentially straighten it, but I wouldn't know of a sure way to determine if it was straightened. Either way I don't know how comfortable I'd be with a bent and re-bent 15+lb mass rotating at 6000 RPM right by my legs. The clutch you purchased didn't come with a pressure plate?
08-17-2005, 08:05 PM
#9
yes i got a pressure plate. it was replaced when i put my spec stage 2 in. is it possible that the pressure plate is causing this intermittent problem? like i posted earlier, sometimes it will engage gears fine, and other times it makes the moaning/ grinding sound when going into gear. at low rpms it engages fine as well. higher rpms its anyones guess as to whether its gonna grind, and what gear its going to grind in... i will find out this weekend, when i get a chance to tear it all apart again.
Last edited by got milk??; 08-17-2005 at 08:11 PM.
08-17-2005, 11:44 PM
#10
update: with the tranny in neutral i reved the car up to 1500 rpm and slowly released the clutch pedal and it duplicated the grinding sound everytime. im thinking its my throwout bearing. anyone else have any ideas or a similar problem?
08-17-2005, 11:53 PM
#11
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not to sound like a dick, but you didnt replace it while you were there?
on a side note, my throwout bearing was the cause of me replacing my stock clutch (although the clutch was nearing the end of it's life as well)
on a side note, my throwout bearing was the cause of me replacing my stock clutch (although the clutch was nearing the end of it's life as well)
08-18-2005, 12:25 AM
#12
the throwout and everything was replaced... hydraulics clutch flywheel everything... all bearings... i just havnt a idea as to whats wrong with it now. like i said with the transmission in neutral.... i revved it around 1500 and slowly released the clutch pedal and it starts to grind.
08-18-2005, 09:20 AM
#13
Grinding is a sign that the clutch isn't disengaging completely.
Put on your thinking hat on how a clutch works...
If it's not disengaging, that means the pressure plate isn't 'letting go' of the disc completely. What causes the PP to let go? The slave cylinder pushing against the fingers. So, either (1) there's air in the lines, or (2) the slave cylinder is positioned such that even when extended with a full pedal throw, it is not pushing far enough on the fingers to disengage the pressure plate.
I see the shim question was asked, but not answered. That impacts my point #2 above... if you didn't shim, that *could* be the problem. The shim is a piece of plastic or something that gets installed between the trans and the slave cylinder.
Put on your thinking hat on how a clutch works...
If it's not disengaging, that means the pressure plate isn't 'letting go' of the disc completely. What causes the PP to let go? The slave cylinder pushing against the fingers. So, either (1) there's air in the lines, or (2) the slave cylinder is positioned such that even when extended with a full pedal throw, it is not pushing far enough on the fingers to disengage the pressure plate.
I see the shim question was asked, but not answered. That impacts my point #2 above... if you didn't shim, that *could* be the problem. The shim is a piece of plastic or something that gets installed between the trans and the slave cylinder.
08-18-2005, 12:47 PM
#15
I think the moaning/goraning you're hearing is the synchros trying to spin up under pressure because the clutch isn't releasing. Grinding (gear clash) in all gears is absolutely a clutch not releasing unless you've managed to blow all the synchros. What exactly was replaced? So far it sounds like you've done the following:
New GM Flywheel
Spec Stage 2 with PP and Shim
Throwout bearing
Have you done anything to the master or slave cylinders? What procedure are you using to bleed the system? What's the clutch fluid reservoir look like? Clean fluid, level only changes when pedal is depressed and returns?
New GM Flywheel
Spec Stage 2 with PP and Shim
Throwout bearing
Have you done anything to the master or slave cylinders? What procedure are you using to bleed the system? What's the clutch fluid reservoir look like? Clean fluid, level only changes when pedal is depressed and returns?
08-18-2005, 01:17 PM
#16
everything replaced:
flywheel
clutch disc and pressure plate
throwout bearing
slave cylinder
master cylinder with drill mod
i have no reason to believe its the transmission synchros because last night i left the transmission in neutral, revved it up to about 1500 rpm and slowly released the clutch pedal. and it made the moan/grind sound.
flywheel
clutch disc and pressure plate
throwout bearing
slave cylinder
master cylinder with drill mod
i have no reason to believe its the transmission synchros because last night i left the transmission in neutral, revved it up to about 1500 rpm and slowly released the clutch pedal. and it made the moan/grind sound.
08-18-2005, 01:45 PM
#17
Doesn't sound like synchros to me either, I thought you were hearing the moaning when you were trying to shift into gear. Could be a bearing you're hearing. Possibly pilot bearing or input shaft bearing. Especially if it happens when you release the clutch while in neutral. If that's the case it's either the friction disc grinding on something or something that's in contact with the input shaft causing the noise.
I'm assuming the grinding you're describing isn't like gear clash that you would hear like if you were shifting without the clutch? It's more like a quiet metal rubbing on metal noise?
I'm assuming the grinding you're describing isn't like gear clash that you would hear like if you were shifting without the clutch? It's more like a quiet metal rubbing on metal noise?
08-18-2005, 02:52 PM
#18
i wish i could of explained it better when it first started happening but i wasnt sure if it was a clutch issue or the transmission but its not a gear clash at all. infact when ur shifting and this happens the gears engage fine. it happens after the gear is engaged and ur letting off the clutch it starts making the moaning and grinding sound.
08-18-2005, 09:56 PM
#19
Well assuming your hydraulics are all in order I'd say it sounds like a bearing, but I'd be very suspicious of the hydraulics. If they're bled properly it should not take several pumps of the clutch to make any difference in the way the car is reacting. Check the master with the hydraulic line to the slave disconnected. It should be so firm that you can't depress the pedal at all. If you can depress the pedal you've either got a bad master or air in the master.
08-18-2005, 11:33 PM
#20
tomarrow im tearing it all apart, im replacing the pilot bearing,replacing the throwout bearing and slave cylinder, inspecting the clutch, and pressure plate, along with doing what u say to the master... any more suggestions, if i put everything back together and it still happens i dont know what to do... maybe replace the clutch again... send my old clutch back to spec and have them inspect it there way.. thanks for all the help this far mike. later