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AMV8 clutch observation

 
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Old 03-21-2014, 11:05 PM
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AMV8 clutch observation

I was running through the first few gears getting on to the hyway, and ended up mishifting into 6th rather than 4th. WOW, talk about a weak clutch. I let the clutch out and it had a 2 second slip before the RPM matched the road speed. sounded REALLY ugly. Ive done this before with my race car and the RPM just drops to the low range with no hesitation. are the clutches in the AMV8 really that weak? I thought because they are so grabby in 1st gear that there was some real strong clamping force, which would give its racing clutch feel when letting it out in first gear. Now that its apparent that its not that strong, I wonder why the clutch feels so grabby in 1st gear just starting out.


maybe its getting time for the aftermarket upgrade clutch package.
 
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Old 03-22-2014, 12:37 AM
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Sounds like yours is almost on its way out XW, I accidentally did that and it dropped right away, your friction material much be almost gone
 
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Old 03-22-2014, 01:56 AM
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Originally Posted by 007 Vantage View Post
Sounds like yours is almost on its way out XW, I accidentally did that and it dropped right away, your friction material much be almost gone
keep in mind, ive had the same stock clutch in my 500ft-lb torque race car, for over 12 years now, so there is no one that is as good to a clutch than me. amazing that someone had done something to this clutch in 22k miles, or its just incredibly weak to begin with.

thanks for the note back!
 
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Old 03-22-2014, 04:20 AM
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I have miss shifted as you describe and clutch slipped but not more than expected, (say zip a touch slow) but did not hook up and kill revs immediately like one would suspect. 62k miles original clutch, and I drive like an old man 90% of the time.
 
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Old 03-22-2014, 07:16 AM
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oo7, you have 62k on the original Vantage clutch? I assumed they all died around 20k, but maybe that's primarily SS.
 
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Old 03-22-2014, 09:20 AM
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Yes, but caveat, I have driven manual Trans for along time and am a little parsimonious and have manual Trans cars with over 200k miles on one clutch a few times. It depends on how you drive.
 
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Old 03-23-2014, 10:08 AM
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I have 27K on my 2009 V8V clutch with no such symptoms as you describe. It grabs hard all the way. I agree with others that it sounds like that for whatever reason your clutch is shot.
 
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Old 03-23-2014, 11:07 AM
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Originally Posted by oo7 View Post
Yes, but caveat, I have driven manual Trans for along time and am a little parsimonious and have manual Trans cars with over 200k miles on one clutch a few times. It depends on how you drive.
I'm guessing you don't look too kindly on drivers that rock their MT car back and forth at a stoplight.
 
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Old 03-23-2014, 11:18 AM
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actually, i dont know if that is true. i dont know if ive ever missed a shift , upshifting on the race car on a WOT acceleration. the reflected forces can be quite high,
the real test will be to go out and do a slight speed shift from 1st to 2nd or 2nd to 3rd and see if it grabs or chirps the tires. IF so, then there is no problem. however, if it spins to catch up, thats a sign of weakness or bad friction pads on the clutch surfaces.

I always like to look at things at extremes to understand the forces. say it takes 1000ftlbs to break the tires free and you can do it up to 2nd if you speed shift. If you did a 2nd to 6th mis shift, the torque on the torque tube and clutch surfaces would be 4x higher if it was to "chirp" the tires, this aint going to happen, so the clutch has to slow the engine down quickly at WOT. how fast it can do that, is the strength of the clutch.

again, i think the quick test if the clutch is ok, is a WOT speed shift from 1st to second... if that works, then i think the clutch might be ok.

I still think these clutches are weaker than other high performance cars. and dont know why AM didnt beef them up with all the technology available back in 2006
 
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Old 03-23-2014, 04:23 PM
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Tire chirp definitely would seem to indicate strong pp and good material, how much material on clutch face would still be an unknown. The common, but debatable test is put in highest gear rev engine with e brake on full and let clutch engage quickly. An object in motion tends to stay in motion and I am alwYs a bit skittish about killing revs real fast as I have seen some very expensive cranks twist from sudden stops. In some cases, most notable in cars that have clutch in transaxle at rear of front engine car, the flex in the drive line plays a role in the ability of the pp to do it's job, which I do not completely understand but I am sure it can be explained . Fortunately few cars were manufactured this way. I was told many years ago that when a clutch is slid excessively the friction material being worn away acts as a lubricant, creating more wear. I am sure though, however, materials used today are better and this may no longer be an issue. XWCGT, did you have the clutch line expansion issue in your race car? I would be very enthusiastic about installing sensors that would measure remaining clutch surface thickness, throw out bearing play and change in pp pressure. Something universal that could be used on all manual cars old and new would be perfect . That's not too much to ask for is it? We already know how many psi our tires have!
 
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Old 03-24-2014, 12:57 PM
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dont want to hyjack this thread guys? but need some advice my vantage has 15600 miles on it and when i park after having it out for a while (ie temps all normal -hot) and I put it into neutral and release the clutch fast there is knock in the drive train like the release bearing coming to a stop almost as if it trys to turn the drive shaft then depress clutch and release fast and it will do it again not a disturbing knock but its apparent, my clutch has no slippage issues even when putting it into 6th gear at low speed and gassing it comments really appreciated
 
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Old 03-24-2014, 04:17 PM
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I know the vantage has a different configuration than I am familiar with, (irish07 knows), but I have had several cars front engine rear Trans cars and they all sound like that when hot. In many, one can hear the torque tube bearings rattle when hot. I believe it is just the slack in the drive line from use. I have driven v8vs with low mileage that exhibited fairly audible noise when only driven 20 minutes. I think it is how the person drove it. When the clutch is depressed, it is quiet, no marble sounds?
 
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Old 03-25-2014, 12:27 PM
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mine is quiet when idling in neutral just if I drop the pedal in neutral I hear this thud noise? it does sound like the torque tube just turning to a point or the slave cylinder just releasing
 
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Old 03-25-2014, 08:10 PM
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Originally Posted by oo7 View Post
Tire chirp definitely would seem to indicate strong pp and good material, how much material on clutch face would still be an unknown. The common, but debatable test is put in highest gear rev engine with e brake on full and let clutch engage quickly. An object in motion tends to stay in motion and I am alwYs a bit skittish about killing revs real fast as I have seen some very expensive cranks twist from sudden stops. In some cases, most notable in cars that have clutch in transaxle at rear of front engine car, the flex in the drive line plays a role in the ability of the pp to do it's job, which I do not completely understand but I am sure it can be explained . Fortunately few cars were manufactured this way. I was told many years ago that when a clutch is slid excessively the friction material being worn away acts as a lubricant, creating more wear. I am sure though, however, materials used today are better and this may no longer be an issue. XWCGT, did you have the clutch line expansion issue in your race car? I would be very enthusiastic about installing sensors that would measure remaining clutch surface thickness, throw out bearing play and change in pp pressure. Something universal that could be used on all manual cars old and new would be perfect . That's not too much to ask for is it? We already know how many psi our tires have!
I pulled the clutch in the race car several times for other reasons., (engine change, chassis change) and the clutch discs were like new. again, still could see the part number ink on the disc surface.
I don't think that technique , of ebrake and release is a good one. I would think a speed shift, 1st to 2nd would be best. if it grabs, you are good, if it slips....well, something is not working. pressure plate has been cooked or the discs are gone or shredded.
 
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Old 03-25-2014, 08:14 PM
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Originally Posted by captain Greg View Post
dont want to hyjack this thread guys? but need some advice my vantage has 15600 miles on it and when i park after having it out for a while (ie temps all normal -hot) and I put it into neutral and release the clutch fast there is knock in the drive train like the release bearing coming to a stop almost as if it trys to turn the drive shaft then depress clutch and release fast and it will do it again not a disturbing knock but its apparent, my clutch has no slippage issues even when putting it into 6th gear at low speed and gassing it comments really appreciated
keep in mind, when you let the clutch out, the torque tube spins. its no different then the front engine front transmission cars. the ONLY diff, is that the transmission is in the rear, and the shaft that comes out of the flywheel is a lot longer . releasing the clutch suddenly, in neutral, spins up the drive line, as it does in any car. putting the clutch to to floor, and the driveline stops (when the car is standing still)
TOB is always spinning , as it is being held in position by a clutch lever arm. different forces exist on the TOB (throwout bearing) when you pus the clutch in. now, the bearing has a lot of axial force on it. but its still spinning , just the same.
 

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