Clutch

[rountreed]

Hi hopefully this is not a dumb question however either way I will ask it. When I am driving on the Autobahn in say 4th or 5th gear at a speed that places the RPMs around 2000-3000 and then step on the gas (HARD) the RPMs rise by about 300-500 before it seems to catch and begin accelerating. Outside that from a stop and go, no problem. At high speeds and high RPMs, again no problems. Please advise, and if it is the clutch about how long do I have before it goes, looking at taking the car to Italy in about 4 weeks for a vacation with my wife before I head back to Iraq.

Thanks

Sorry, car is

2000 Porsche 996 CA4 CAB with 34000 miles

[DeAd-EyE]

it sounds like its probably the clutch but because it isn't too severe, i wouln't loose sleep over it as you prolly still have a loong ways to go b4 it craps out on you for the last time (I'm talkin thousands of kms here).

In my opinion, it will be fine for your vacation. now get a bullet proof hardtop and take that thing to bhagdad with you when your done. :)

[threeOh]

Is it engine management cutting in?

Mine (X51) cuts in at a touch over 3,000 rpm. Try putting the car in second gear and accelerate moderately. If you feel a transition, note the rpm and then go back to the autobahn.

[geza]

Hi hopefully this is not a dumb question however either way I will ask it.  When I am driving on the Autobahn in say 4th or 5th gear at a speed that places the RPMs around 2000-3000 and then step on the gas (HARD) the RPMs rise by about 300-500 before it seems to catch and begin accelerating.  Outside that from a stop and go, no problem.  At high speeds and high RPMs, again no problems.  Please advise, and if it is the clutch about how long do I have before it goes, looking at taking the car to Italy in about 4 weeks for a vacation with my wife before I head back to Iraq.

Thanks

Sorry, car is

2000 Porsche 996 CA4 CAB with 34000 miles

<{POST_SNAPBACK}>

Sounds like textbook clutch slippage - the standard test is what exactly you describe: high gear, ideally going up a hill, open the throttle and feel slippage through increased revs without matching increase in speed. It is the beginning of the end for the clutch - but it will be a while yet. Hard to say how many miles to go before you start getting the same effect in 1st & 2nd gears - at that point, it will deteriorate rapidly.

You should be OK for the vacation - take it easy, baby the car. For complete peace of mind, maybe you could get the clutch replaced before you go?

[rountreed]

Thanks, was afraid it was the clutch, could I get it replaced sure! but I think I will wait since the car will go in the garage for storage while I am gone and do not want my wife to worry about it and if we must we can take the Volvo, just not as much fun but much better storage for the luggage. The strange thing is if I drive it and change above 4000 rpm there is 0 lag in the rpms but I am still learning as a Corvette guy who married a German and changed to Porsche.

[1999Porsche911]

If your clutch as slipping at a low rpm, low torque point (high gear), you would notice an even more severe slippage in lower gears. Because you are not experiencing this, I doubt it is the clutch.

[wwest]

If your  clutch as slipping at a low rpm, low torque point (high gear), you would notice an even more severe slippage in lower gears.  Because you are  not experiencing this, I doubt it is the clutch.

<{POST_SNAPBACK}>

NOT!

In lower gears the torque level that the clutch can "couple" without slipping is multiplied downstream and so there is actually less probabilty of clutch slippage.

Try starting out in 4th gear from a full stop as a perfect example of this, clutch will slip every time yet work perfectly in proper startup gear.

[1999Porsche911]

If your  clutch as slipping at a low rpm, low torque point (high gear), you would notice an even more severe slippage in lower gears.  Because you are  not experiencing this, I doubt it is the clutch.

<{POST_SNAPBACK}>

NOT!

In lower gears the torque level that the clutch can "couple" without slipping is multiplied downstream and so there is actually less probabilty of clutch slippage.

Try starting out in 4th gear from a full stop as a perfect example of this, clutch will slip every time yet work perfectly in proper startup gear.

<{POST_SNAPBACK}>

That is not true. If your clutch slips in 4th gear when you slam it at 3000 rpm, it will slip even more slaming it at 3000 in 1st gear. The clamping force of the plate is not determined by rpm or what gear you are in. If it is weak in one gear, it is weak in all gears. If the disc is glazed and causes slippage in one gear, then the glazing will cause slippage in all gears at the same or greater torque. Not my rule, just phsycs.

[geza]

That is not true.  If your clutch slips in 4th gear when you slam it at 3000 rpm, it will slip even more slaming it at 3000 in 1st gear.  The clamping force of the plate is not determined by rpm or what gear you are in.  If it is weak in one gear, it is weak in all gears.  If the disc is glazed and causes slippage in one gear, then the  glazing will cause slippage in all gears at the same or greater torque.  Not my rule, just phsycs.

<{POST_SNAPBACK}>

I feel this needs clarification, purely from a technical perspective. We all know that 1st gear is very short, and 6th is very long. Each interval (gear) between enables the engine speed (rpm) to keep within it's rev limits (idle to red line) all the while increasing road speed - while you are moving from 1st to 6th. Moving the car from a standing start is easiest in 1st, where there is a great reduction in engine speed through the gearbox to lowest road speed - using torque to get the car off the mark. This means that the force feedback from the road to the engine is greatly reduced - making it very easy to move the car. This same effect makes life easy for the clutch - as it can transfer the engine power since the 1st gear reduction is effectively the easiest path to start movement of the car. When you do a maximum throttle launch of the car from 1st gear, the clutch slips initially as part of the process until the pressure plate is fully clamped.

On the highway, the car in a higher gear is more difficult to move rapidly. It in effect becomes the immovable object, while the engine is commanded through the throttle to continue to become the unstoppable object in terms of force applied to the clutch - which is the slave in between.

As the engine produces its maximum torque - which is fairly flat from 3k rpm through 5k rpm, we have the opportunity to see how the clutch deals with the force in very clear perspective. If when applying throttle firmly the revs rise, without an increase in road speed in a manual transmission car, the clutch is slipping.

Noticing this effect in 1st gear is extremely difficult when the clutch is first starting to wear because if you accelerate hard, there will be slippage for a brief time, but the rev rise so quickly at low speed with little rolling resistance from the vehicle or frontal air resistance that it takes a well trained technician to feel the transition from grip to slip, back to grip.

I do agree that if the clutch is very badly worn/flywheel glazed, you will get slippage in all gears. In this case, it appears that rountreed's clutch is just starting to show signs of slippage

[threeOh]

Guys,

This is what was said.

"When I am driving on the Autobahn in say 4th or 5th gear at a speed that places the RPMs around 2000-3000 and then step on the gas (HARD) the RPMs rise by about 300-500 before it seems to catch and begin accelerating. Outside that from a stop and go, no problem. At high speeds and high RPMs, again no problems. Please advise, and if it is the clutch about how long do I have before it goes, looking at taking the car to Italy in about 4 weeks for a vacation with my wife before I head back to Iraq."

While the symptoms don't rule out clutch, the RPM's are not rising. "It" in "seems to catch", is referring to the car, not the clutch.

Check when engine management cuts in. My X51: below 3,000 RPM its leisurely, above 3,050 it immediately hits and its a trip. Don't know what a standard 996 is like.

There are few places in Germany to push a car and notice engine management. With what rountree is doing on the Autobahn may be the only time he feels the transition.

[uimtiaz]

My clutch on a 99 C2 is experiencing the same slipping. I took it to my porsche mechanic. He has quoted me about 11 hours of labor to replace the clutch. For others that have gone through this, what has been the ballpark cost for a clutch replacement.

thanks

Umar

[DeAd-EyE]

My clutch on a 99 C2 is experiencing the same slipping. I took it to my porsche mechanic. He has quoted me about 11 hours of labor to replace the clutch. For others that have gone through this, what has been the ballpark cost for a clutch replacement.

thanks

Umar

11 hours seems rather excessive...it should be more in the regieon of 6 hrs. this would include dropping the tranny and installing the new clutch.

did you take it to an independent or a dealer?

[uimtiaz]

i took it to these guys at http://www.autosportengineering.com/

they seem really nice, but a 5 hour discrepancy does seem like much

thanks

umar

did you take it to an independent or a dealer?

[1999Porsche911]

Here in Chicago, total cost including OE clutch kit is $1200 at Euroquip.