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-   -   Trying to save the last of my clutch (http://986forum.com/forums/showthread.php?t=18006)

Lordblood 08-24-2008 07:07 AM

Trying to save the last of my clutch
 
This is actually a pretty basic question, but only because this is the first manual car I've driven (and taught myself).

But my clutch is almost gone, and I want to save the last bit of it as long as I can. So my question is when I change gear (1st to 2nd, 4th to 3rd, etc) is it better to dump the clutch right back in or should I hold it at the biting point and slowly let the clutch back in from there?

Lil bastard 08-24-2008 07:28 AM

The longer you hold the clutch, the longer it is wearing against the flywheel. The clutch compound is softer and so it wears.

You should really engage as soon as you can without jarring it or stalling the engine. As soon as the clutch and flywheel are fully engaged and turning together, the better.

The is a specific rpm at any speed and gear combination where the flywheel and the clutch are turning at or near the same rate. Shifting at these points will cause the least wear. It takes some learning to discover where these rpms are, but when you hit them, you'll notice very little disturbance or shudder, the clutch just seems to slip right in.

People who double-clutch use this technique, where they 'blip' the throttle to match revs with the clutch. This not only saves the clutch, but wear to the synchros, bearings and cv joints too. Racers use it because they can keep the engine in it's 'sweet spot' and don't have to build the revs/power again.

There are other things you can do to baby the clutch too. Don't hold the clutch in at stoplights or signs, go into neutral and release the clutch completely. Don't ride the clutch, get you foot off the pedal as soon as you can and don't get on it until the very last moment. Don't use the clutch to hold the car on an incline or hill. And in city driving, anticipate your stops and downshift as little as possible, coast (in gear w/o lugging the motor) and use the brakes to slow/stop the car. All these things will reduce wear on the clutch and extend it's useful miles.

Lordblood 08-24-2008 07:36 AM

I have noticed the RPM thing, I'll just switch up and let go of the clutch (not vigorously, but not holding it at the biting point and letting it up slowly) and the car just engages the gear I want without much fuss.

Thanks for the tips, I pretty much do everything you said, other than matching the revs. Blipping the throttle is only for downshifting tough, right?

Tool Pants 08-24-2008 07:40 AM

The clutch disc is held together with rivets. Once the friction material is worn out the rivets can contact the metal surface of the flywheel and/or pressure plate and score the metal surface.

If the pressure plate gets scored it does not matter, because a clutch kit included a new pressure plate. If the flywheel gets score, then it is resurfaced or replaced. Some shops will not attempt to have a flywheel resurfaced. That means a new flywheel and retail is $900.

You might want to do a clutch replacement now.

Cloudsurfer 08-24-2008 08:21 AM

I'll second Tool Pants on this one. If you know (how do you know, by the way?) that your clutch is on its last leg, it will be MUCH cheaper to replace it now and save your flywheel than it will be to have to buy a clutch kit AND flywheel after the rivets score the flywheel. Most shops will not attempt to resurface a dual-mass flywheel (which your car has, unless its been replaced by a lightweight previously, which is doubtful).

Patrick

Lordblood 08-24-2008 08:28 AM

Quote:

Originally Posted by bmwm750
I'll second Tool Pants on this one. If you know (how do you know, by the way?) that your clutch is on its last leg, it will be MUCH cheaper to replace it now and save your flywheel than it will be to have to buy a clutch kit AND flywheel after the rivets score the flywheel. Most shops will not attempt to resurface a dual-mass flywheel (which your car has, unless its been replaced by a lightweight previously, which is doubtful).

Patrick

I had it checked at a mechanic before I bought the car about a month ago. One of the things that was wrong with this car (the list was quite small) was the clutch, which has 90,000 miles on it, and was quite worn.

If I do change the clutch, I would get the oil leak fixed as well as a 90k maintenance, although I could probably do the 90k myself.

Lil bastard 08-24-2008 08:35 AM

Quote:

Originally Posted by Lordblood
Blipping the throttle is only for downshifting tough, right?

Not really, If you upshift and keep the clutch in, you'll notice that the engine returns back to near idle (low rpms). Give it some gas as you release the pedal (not too much) and you'll notice the upshifts are smoother.

In the famous chase scene in the Steve McQueen classic 'Bullitt', one of the gripping FX is the sound of McQueen double-clutching on the upshifts as he pushes his Mustang to catch the bad guys in the Charger. He wasn't thinking clutch preservation, he was trying to keep the engine in the power band, but he was helping the clutch too.

Lil bastard 08-24-2008 08:36 AM

Quote:

Originally Posted by Tool Pants
The clutch disc is held together with rivets. Once the friction material is worn out the rivets can contact the metal surface of the flywheel and/or pressure plate and score the metal surface.

If the pressure plate gets scored it does not matter, because a clutch kit included a new pressure plate. If the flywheel gets score, then it is resurfaced or replaced. Some shops will not attempt to have a flywheel resurfaced. That means a new flywheel and retail is $900.

You might want to do a clutch replacement now.

Absolutely great advice! I didn't even think of that, good call !

FrayAdjacent 08-24-2008 09:30 AM

You could just match revs and shift without using the clutch.... well, in all but 1st gear.

Cloudsurfer 08-24-2008 10:15 AM

If you've got 90K on your clutch, I can assure you its time to come out. However, do realize that without pulling the transaxle there is no way to inspect the clutch. So, whatever "report" you got was purely subjective with respect to wear. To that end, I'd be surprised if the first clutch lasted 90K?

Patrick

blue2000s 08-24-2008 11:38 AM

What is it that the clutch is doing that makes you feel that it's almost worn out?

Tool Pants 08-24-2008 12:23 PM

As Bmwm750 pointed out it is a dual mass, aka dual mess flywheel. None of the dealerships in my area will play around with it, just like they will not resurface brake rotors. I only know 1 independent shop that will consider having it resurfaced, but you get the warning if it does not work properly....

And speaking of messes. Here is the clutch disc from an autocross champion. And yes, he also needed a new flywheel.

Cloudsurfer 08-24-2008 02:19 PM

OUCH!!!!

Patrick

Lil bastard 08-24-2008 02:28 PM

With that clutch, I hope at least he had the low e.t. :D

Paul 08-24-2008 07:13 PM

Quote:

Originally Posted by FrayAdjacent
You could just match revs and shift without using the clutch.... well, in all but 1st gear.

NOT! Unless you want to add a tranny to his repair list. I've been hearing this since the 70s and it always ends up with a rookie standard shift owner destroying his tranny.

Lordblood 08-24-2008 08:22 PM

The biting point is quite high, and before I bought the car an independent mechanic (specializes in Ferrari and Porsche) diagnosed a worn out clutch and small oil leak as the two main things wrong with the car, apparently a 1700 dollar repair altogether.

blue2000s 09-02-2008 05:38 AM

Quote:

Originally Posted by Lordblood
The biting point is quite high, and before I bought the car an independent mechanic (specializes in Ferrari and Porsche) diagnosed a worn out clutch and small oil leak as the two main things wrong with the car, apparently a 1700 dollar repair altogether.

Clutch slipping in high gear is the best way to tell if it's on it's way out. If you're in 5th gear, you hit the gas and the RPMs rise but the car doesn't speed up, you're clutch is on it's way out. There's no need to replace it if it's not doing this and it isn't damaged in some other way.

Brad Roberts 09-02-2008 09:31 AM

Quote:

The biting point is quite high,

This is the sign that ALL push clutches exhibit when the disc is getting thin. Same for 964's/993's/986's/ everything.. Your mechanic is correct. The disc is worn.

Someone above was trying to tell you to shift at peek torque for each gear. You *should* be able to do this by feel.

Double clutch up or blip down? Not on the street. Complete wast of gas blipping down on the street. Even my pro drivers only blip into the actual gear they need to conserve GAS.

You can lift throttle upshift these tranny's at peak torque. They are NOTHING like the early 901/915/930 boxes of yesteryear. These have Borg-Warner synchro's in them just like the Vettes and Vipers do. I don't recommend it driving it this way for very long, but if the clutch fails on you.. you certainly can to get it wherever you need to. Clutch fails: put it in first gear with the engine off and start the car with it in gear. It will shutter, but it will start and take off in first, then bring the engine up to peek torque, lift throttle, and pull the shifter back into second. Come to a light? lift throttle and take the car out of gear, shut it off, coast.. come to stop put it in 1st, hit the starter again when the light goes green.

Long before you do that :) Get AAA Your starter will thank you for it. The above technique should be used when out in the middle of nowhere. I have driven a Boxster from San Jose to LA with no clutch. I only stopped once to use the mens room :)


B

blue2000s 09-02-2008 09:59 AM

Quote:

Originally Posted by Brad Roberts
This is the sign that ALL push clutches exhibit when the disc is getting thin. Same for 964's/993's/986's/ everything.. Your mechanic is correct. The disc is worn.
B

Even if the biting point is high, if it's still gripping, the clutch is still working. If you wait until it slips, you have used it to the end of it's life. Why replace it before that?

Dragonwind 09-03-2008 10:29 AM

This got me thinking that I should get mine done sooner rather than later. My car is about to hit 70k and the clutch still seems okay, but you never really know. Well, here goes another big expense but rather do this than blow the clutch at an AX event.
Chris


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