Slipping
05-04-2010, 11:59 AM
#17
Rennlist Member
Yes but less common I believe.
05-04-2010, 12:36 PM
#18
Race Director
Over the past 3 months with 1500 miles, I have a random slipping problem (slipping - meaning it is in gear with little or no power and revs jump while attempting to accelerate). The first time this happened I thought either I was not in gear or it popped out - but that was not the case. This is with my 2004 911 turbo - 30k miles. I have driven this car around 40 times and have had 5 instances of slipping over the past 3 months. The strange thing is that I have noticed it in 2nd/3rd/4th gears. When I punch it while in 6th gear going slow - no slipping. Also, I have seen bar as high as 1.6 without slipping (in 3rd/4th gears). Out of the 5 times, 2 slipped quite bad (causing a burning smell - like the old electric race track cars when you let the wheels spin). During these 2 times, I noticed that the slipping began in 2nd and kept slipping into 3rd gear as well.
I have had bad clutches in the past, but none that behaved like this - so I need some feedback. I have talked to a couple of porsche mechanics and all say clutch. I would expect more consistency in the slipping if it were a clutch problem.
The strange thing is that when it does happen, if I pause and let the clutch engage - the slipping does not happen. It only happens when shifting gears quickly.
Any ideas - I would appreciate the feedback.
I have had bad clutches in the past, but none that behaved like this - so I need some feedback. I have talked to a couple of porsche mechanics and all say clutch. I would expect more consistency in the slipping if it were a clutch problem.
The strange thing is that when it does happen, if I pause and let the clutch engage - the slipping does not happen. It only happens when shifting gears quickly.
Any ideas - I would appreciate the feedback.
I believe the 996 Turbo can suffer from motor mount problem that can allow the engine to twist and interfere somehow (the mechanics of how this can happen are not clear to me) with the linkage and cause slipping when one would not expect it.
One symptom is the engine rpms race under acceleration in the higher gears.
You'll need to have this looked at, into. It will only get worse and could ruin the flywheel from overheating it from the slipping. It will certainly not get better by you continuing to reproduce the behavior.
RMS can leak but these engines are not prone to this leak like the engines in the non-turbo cars. These engines are not the same engine as the non-turbo car engines and do not suffer from their common ills.
For the RMS to leak enough to foul the clutch/pressure plate -- which in my reading is rare -- I believe you'd see oil under the car and under the transmisison/bellousing/engine. Even in cases where the oil doesn't foul the clutch (far and away the most common case) the leak is in evidence by the signs of oil under the engine, transmission, bellhousing, and on the floor under the car.
With the engine removed and the transmission off the car the tech will easily be able to see if there's any leakage and at that time you can have a new seal installed. My guess is the existing seal will be upon observation to be oil tight.
Get the clutch looked into. Have motor mounts and linkage checked to eliminate this possibility. If everything looks good outside then the clutch will have to be looked at.
Oh, 1.6 bar boost? That's about double what these engines should produce stock. Is the engine stock? If it is stock then there's something causing excessive overboost and this needs looking into and right now. The engine's at risk if that boost number real.
If the engine is not stock and the 1.6 bar boost real and not indicative of some engine problem (or gage problem) then the modified engine and its higher boost levels and resulting increased engine output is overwhelming the stock clutch. An aftermarket clutch will be required.
Thus have the clutch linkage and motor mounts checked out and given a clean bill of health. Have the cause of the overboost found and fixed. Diverter valves maybe? I am not sure.
Then if clutch symptom still present time to tear into the clutch and fix what's wrong.
Sincerely,
Macster.
05-04-2010, 01:19 PM
#19
7th Gear
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What is interesting is that it was just serviced and nothing was found. Since the servicing, it has not happened (but since it is random this may not mean anything).
1.6 bar boost - the previous owner has a performance upgrade performed at a porsche dealership. But no slipping when it hit this.
1.6 bar boost - the previous owner has a performance upgrade performed at a porsche dealership. But no slipping when it hit this.
05-04-2010, 01:55 PM
#20
Race Car
You're not slipping 6th probably because you are lugging the motor so hard it cant make the torque/boost needed like the lower gears.
But, I wonder if your throwout bearing isnt being released as quickly as it should holding slight pressure on the pressure plate.
Maybe a sticky throwout bearing sleeve.
But, I wonder if your throwout bearing isnt being released as quickly as it should holding slight pressure on the pressure plate.
Maybe a sticky throwout bearing sleeve.
05-04-2010, 10:58 PM
#23
Race Car
j/kI would gladly take a look for you, that is totally up to you. PM if you like.
But, if you want the best Porsche mechanic in San Antonio, see Bob Jones at Jones Autowerks. I have talked with him and he was factory trained back in the day. He gave me a good amount of info for my motor and was easy to speak with. His shop is quite impressive too. Their # is 657-1111
