Warning signs your clutch is about to go?

[autobonrun]

After all the recent work on my exhaust system to increase HP, it struck me that I could be losing HP at the tire if my clutch was slipping on acceleration. A catastrophic failure is a no brainer, but what are the warning signs that a clutch is nearing the end of its useful life?

I thought I detected slippage (sounded like tire spin but they weren't) recently during a hard acceleration. It just did it once so I attributed it to the way I released the clutch that time. I replaced my first clutch at 101k miles and I'm at 200k now so I'm probably getting close to its useful life. This is a very expensive repair, but would you wait for a total failure before you replaced it or would you treat it as a scheduled item based on prior history?

Lastly, are any of you using the low mass aluminum clutch sets or are you sticking to the standard?

thanks for any input

79 911SC Targa

[Doug Zielke]

When you can't adjust the free-play to spec, I'd say she's toasted.

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'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
The Blue Bomber's Website

[john walker's workshop]

80K is average clutch life. some more, some less. accelerate up a hill, and in the process, quickly depress the clutch and release it without lifting the throttle. did the clutch grab instantly, or did the RPMs stay up a second or more as the clutch slipped? that's the best diagnosis i know. the flywheel is the only thing you'll sacrifice to get the last mile out of a clutch.

[autobonrun]

Originally posted by john walker's workshop:
80K is average clutch life. some more, some less. accelerate up a hill, and in the process, quickly depress the clutch and release it without lifting the throttle. did the clutch grab instantly, or did the RPMs stay up a second or more as the clutch slipped? that's the best diagnosis i know. the flywheel is the only thing you'll sacrifice to get the last mile out of a clutch.

Thanks for the advice! I'll try this test tomorrow. I would have never thought to do this. Sounds like I can drive it to the last rather than trying to predict when it will go. I do think I'll set aside a few dollars each month in advance. I can't have too much left with 100k miles on this clutch.

[Doug Zielke]

Hey John,
What ya drinkin' tonight?
That sounds like a pretty harsh test for the clutch. But real good for business...

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'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
The Blue Bomber's Website

[Superman]

I will look for a convenient time to replace my clutch when it gets weak, and if mileage is up there like yours is. But in my days of driving basket cases, I'd wait until it could not pull a hill in high gear. the slippage is very smooth and it will be in high gear that it will give up, if it's gonna. They go out pretty slow.

Then again, I think John is warning against going too long, allowing the clutch to chatter and heat up the flywheel.

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'83 SC

[twin plugged targa]

similar to John W's suggestion I have always tested cars by selecting 2nd gear with parking brake on and try to pull away. If clutch slipps - bad. if engine stalls immediatly then good!
crude but simple!.
Some may concider this a bit harsh on the clutch/drive train but I use it when doing a pre purchase inspection and would rather find out if the drive train is weak before I shed out the cash!
hope this helps
Ben

[Superman]

That's the method I've used too, Ben, but I like John's test. I think John's test would give a better indication of a weak but not yet fully worn. Both tests are somewhat hard on the car, but not that hard. Certainly worth it if you're suspicious.

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'83 SC

[john walker's workshop]

no harder than normal driving. no more friction than taking off from a stop really. you're only depressing the pedal for a split second.

[Pillow]

My clutch is toast, but I still run it anyway.

If you are gentle to the clutch you can nurse it for a while... Then again not too long because you will burn the flywheel.

If I rev her up and dump the clutch at a standstill it will not move... I did this only once, but the clutch smell was nasty! Also mine slips in the higher gears when I am on the gas.

Granted if you just putter around you will not notice the clutch slipping at all. 90% of my driving.

Yes, I should get a new clutch... Just lazy because I do not drive it much. But it will still autocross just fine

My lazy $.02,


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Adrian Pillow
1979 911 SC
1966 VW Microbus
PCA - Peachstate Region

[Don in Redondo]

I think what John W. was warning about, is that if the clutch disk wears too much, the attach rivets become exposed and begin to eat into the flywheel, which will make a heck of a racket, and necessitate a flywheel resurface or replacement.

[RazorRacer]

With a rubber center clutch (1978), will it drive fine cold, but slip when it gets hot?

[Jgordon]

Racer, that's what I'm going through. I'm fine with the performance 90% of the time, but in stop and go traffic, if she warms up too much, she'll start slipping like crazy. My remedy so far has been to try and avoid stop and go traffic, which seems to be working. I think this kind of thing is universal, but I have a G50, so I'm not positive. If it only happens when it's real hot, and you can avoid getting it that hot, I'd say stick with it a while longer and nurse a couple more miles (dollars) out of it.

Jared

[Superman]

Jared, I have a tip for you. Don't know if this will work but you might try adjusting your pedal to get more freeplay. I know this is counterintuitive, but I once had an odd problem with a hydraulic clutch mechanism. The freeplay was adjusted so small that the clutch master cylinder piston was not retracting all the way. Because of this, fluid could not move between the MC and the fluid reservoir. When warmed, this (closed) system would build pressure press against the release bearing, making the clutch slip. Of course, if your clutch is simply worn, then this won't work. It's a longshot, but I rebuilt a clutch needlessly because of this. In a 4WD vehicle!

Razorman, usually a failed rubber center clutch will just stop disengaging. That is, depressing the clutch pedal will not disengage the engine from the tranny, like a clutch is supposed to do. This is because the rubber gets stuck between the flywheel/disk/pressure plate parts, keeping them from being independent of one another.

[emcon5]

Just for another data point, when my clutch went on my 82, it never slipped. The first sign that is was going was the gentle scraping noise, as the rivets went to work on my flywheel.

My old truck and mustang both slipped like hell when the clutch wore out.

Tom

[john_colasante]

I had a friend who drove so long on a bad clutch on his VW Scirocco that gunning under full throttle would only move the car a few inches at a time. That was funny stuff.

[Kurt B]

Drive it til something explodes, or you can no longer accelerate uphill.

That's the easiest way to determine a clutch problem. Or any problem for that matter.

Spare the rod and spoil the child (911)