how to save yourself some $$$ when replacing your clutch

[apapada]

No offense to apapada but I state a few things differently.

No offense taken. This is the type of info exchange that makes these boards so great.

Originally posted by sjs
especially those with carbon buildup, too much ignition advance around idle, over heating, crappy gas, lean mixture, "lugging" it, or a combination of these and other conditions.

At that point, I'm afraid that a clutch longevity is the least of one's worries, don't you ?

Originally posted by sjs
Yes the clutch is designed to slip, but your explanation of it's purpose in life could be misleading. It is designed to slip slightly to smooth the transition as you couple the engine flywheel to the input shaft of the transmission. That should occur only while the clutch pedal is in motion, but your description makes it sound more like a torque converter. I know what you mean, but a newbie might think it slips during other times to sync up the engine and tranny.

If my description could be misleading, I'm glad you clearified this point.

Originally posted by sjs
The problem with most "tests" you can tell people to run is that they won't do it right and cause still more wear. Your rest in particular is a bad one. Someone with a feel for it knows when it happens anyway, but perhaps a better test is to drive along in 4th or 5th gear at ~4500 RPM, press hard on the accelerator and firmly enough on the brake to begin slowing the car. Then again, a novice may not recognize the slip and end up smoking the clutch further.

I respectfully disagree on this point. Although I recognize that the test I propose might not be the "best" as you put it, I would positively recommend against anyone trying the "test" you are prescribing. The simple fact of the matter is that such a test would be extremelly dangerous for a "novice" (as you put it) performing such a manoeuvre cruising at 4500 RPM in 4th or 5th gear and stepping on the brake while accelerating, if not completely illegal (how fast is an 5spd or 6spd going in 4th or 5th at 4500RPM anyway?). Eventhough not the "best test" out there, the one I'm proposing can be performed legally anywhere SAFELY (no motion involved) and does not involve high speeds like the one you are suggesting. just my $0.02

 

[nsxtasy]

Why do you need to test whether your clutch is slipping in the first place? That sounds like testing whether your engine is stalling at idle, or your window won't raise from inside the door, any other problem. There's no need to test for a possible problem; either you observe the symptoms (in which case you get it fixed) or you don't.

(By saying this, I'm not trying to flame anyone or be facetious; I just don't understand...)

 

[sjs]

You're right about the speed at 4500 in 4th or 5th. That occurred to me as I headed home from work late that same night so I mentally revised it to a more sane 3rd gear. Easy to forget that these cars are not geared the same as those I grew up with. I went ahead and ran the test on the way home and was pleased to find that my clutch still grabs at a decent load level. As for being unsafe, so is driving 60mph if done carelessly or in the wrong place. Get on a wide empty highway, cruise along at 4500 (in 3rd) and I don't see any danger. I'm not talking anything dramatic, just dragging the brakes while giving it some gas. Anyone who can't do that safely needs to use public transportation. Note: By “novice” I meant in an automotive technical/mechanical sense, not some who just got their driver’s license.

I still don’t like the parking lot handbrake test. You may do it correctly, but many people will end up harming their clutch by being too timid in the release and end up with false results as well. Note to FWD car owners: This test is not for you.

Why to do such a test? I agree that for the most part it is pointless, but not entirely. When dealing with modifications that increase torque and HP it can help determine whether a particular clutch is up to the task since even a new one will slip if asked to transmit too much power. And as in my case, and possibly this one, it does allow one a quick check under controlled conditions to see if there is a problem on the near horizon because the test will uncover it earlier than would be noticed under normal driving conditions. I’ve done it before buying a used car as well.

BTW, the same technique is also a crude but effective way to achieve a broader range of load/RPM conditions when tuning a turbo system. It allows you to hit far more "cells" on the fuel map, simulating acceleration up hills etc.

 

[RP-Motorsports]

Ken, Here is a true story about Steve S's NSX.

It was a couple of days before Windy City RA 2002 and he asked me to come over and install some pedals in his 91. I did so and then took it out for a test drive to check clearance for heel and toe. Steve usually takes his car to 4k rpms the first two gears when he starts out driving his car. I did not want to be accused of driving his car "hard" while on a test run, so as I pulled out I purposely short shifted the first 3 gears when I immediately noticed something.........his clutch was slipping!!!!! It is easier to "notice" a slipping clutch to short shift to 4th gear around 40mph and put the gas to the floorand watch the difference in rpm's -vs- mph. In Steves car the clutch slipped bad doing this. He never noticed this before cause he was always hard on the gas and it is hard to feel the slippage. He did not believe me, so I made him drive it and short shift when he immediately felt/saw the slipping. After he said "#*@%" he cancelled the Windy City event risking a $500 investment with a dead clutch on the track.
A few months later AOB installed a new clutch I think a Dali one....not sure. They did confirm a worn out disc. With his new clutch installed he said his car felt 100 times stronger/faster!!!!

 

[sjs]

Ken, Here is a true story about Steve S's NSX...

I too am Steve S, but obviously not the one referred to above.

Good example of a case where someone can have a problem and not even know it. For most people a clutch must be very bad before they realize something is wrong. At least the first time around.

 

[apapada]

Note to FWD car owners: This test is not for you.

May I ask why ? I have successfully diagnosed FWD cars with bad clutches in the past using this technique...

 

[apapada]

It is easier to "notice" a slipping clutch to short shift to 4th gear around 40mph and put the gas to the floorand watch the difference in rpm's -vs- mph.

doens't suprise me at all... in fact, on a vehicle I know, that's how I first always notice that a clutch is going bad. Then I do the test I described above and usually it helps to confirm my initial observations. If the engine dies slowly the clutch is going bad. If the engine fails to die, it's time for a new clutch ASAP.

 

[nsxtasy]

Why do you need to test whether your clutch is slipping in the first place?

Thanks, guys, for the explanations. Makes sense.

 

[apapada]

Thanks, guys, for the explanations. Makes sense.

Maybe one is buying a used car and would like to find out first hand if the clutch slips too much or not. Or maybe one feels his clutch may be slipping and wants to find out for sure...

others, any other reason why ?

 

[sjs]

May I ask why ? I have successfully diagnosed FWD cars with bad clutches in the past using this technique...

Well I imagine that most of them still have rear parking brakes, or is that not true? (Not like I'd ever own one or anything. ) With a rear brake I would think you'd risk spinning the front driven wheels. Or don't wrong-wheel drive cars make enough power to spin the tires? (kidding) With rear drive and rear brake you aren't relying on just the static friction of two tires on the pavement to hold you still.

 

[apapada]

Well I imagine that most of them still have rear parking brakes, or is that not true? (Not like I'd ever own one or anything. ) With a rear brake I would think you'd risk spinning the front driven wheels. Or don't wrong-wheel drive cars make enough power to spin the tires? (kidding) With rear drive and rear brake you aren't relying on just the static friction of two tires on the pavement to hold you still.

If you manage to spin the front tires on DRY, with a FWD car using this technique then:

#1: your clutch is definetly fine (for how long is another story)
#2: you got a helluva parking brake
#3: you've got crappy tires

If you manage to spin the front tires on DRY, with a RWD car using this technique then:
#1: you've got a problem

 

[sjs]

Yeah, you're probably right. About all I know of FWD is that they can be made to do some very trick reverse gear maneuvers in the snow, and other than that I don't have much use for them.

 

[Tantheman]

Great thread.

Tan