Vibration at 2900-3100 rpm
09-08-2003, 02:48 AM
#31
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In response to Erik's posts, I can fill in a bit more details wrt. my broken drive shaft:
1) I had never experienced vibration in the car at any rpm range, no strange noises or other indicators that could have made me aware of what was going to happen.
2) The car had about 55K miles on it when I bought it - I have no idea how the PO treated it - but have a feeling that it was OK, but absolutely not as I would expect with a vehicle of this class.
3) I had subjected the car to two Porsche driving events - one where the focus was on safe driving (i.e. wet driving/braking, evasive maneuvers etc.) - and one day of full-speed, agressive track driving where I shifted the AT semi-manually (i.e. using 2 and 3 through the slow corners).
4) When the shaft finally broke, it was during sedate driving in the city. A 3-2 downshift ripped the final "strands" of material over and I lost the physical connection between engine and transmission.
5) Looking at the bits of the driveshaft, I appeared that it had simply been over-torqued (I think Erik has posted a link for the photos).
It cost me about $4000 to have it fixed, so it is not something I plan on repeating every other year!
6) Wrt Erik's assumption of driveshafts not increasing in O.D., I can safely say that that is NOT the case. My mechanic attempted to source a shaft from an earlier model, but when comparing to the one in place on my GTS the difference was in the order of 5-8 mm.
So I think that Porsche did their homework and re-engineered the shaft for the more powerful models, however, it's not to say that it is strong enough anyway (as my incident clearly shows).
Not much help in this post, but I hope that someone can pick up some useful information from my sad experience.
Regards,
1) I had never experienced vibration in the car at any rpm range, no strange noises or other indicators that could have made me aware of what was going to happen.
2) The car had about 55K miles on it when I bought it - I have no idea how the PO treated it - but have a feeling that it was OK, but absolutely not as I would expect with a vehicle of this class.
3) I had subjected the car to two Porsche driving events - one where the focus was on safe driving (i.e. wet driving/braking, evasive maneuvers etc.) - and one day of full-speed, agressive track driving where I shifted the AT semi-manually (i.e. using 2 and 3 through the slow corners).
4) When the shaft finally broke, it was during sedate driving in the city. A 3-2 downshift ripped the final "strands" of material over and I lost the physical connection between engine and transmission.
5) Looking at the bits of the driveshaft, I appeared that it had simply been over-torqued (I think Erik has posted a link for the photos).
It cost me about $4000 to have it fixed, so it is not something I plan on repeating every other year!
6) Wrt Erik's assumption of driveshafts not increasing in O.D., I can safely say that that is NOT the case. My mechanic attempted to source a shaft from an earlier model, but when comparing to the one in place on my GTS the difference was in the order of 5-8 mm.
So I think that Porsche did their homework and re-engineered the shaft for the more powerful models, however, it's not to say that it is strong enough anyway (as my incident clearly shows).
Not much help in this post, but I hope that someone can pick up some useful information from my sad experience.
Regards,
09-08-2003, 05:04 PM
#33
Burning Brakes
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Originally posted by Erik - Denmark
I found two good write-up regarding this matter, see:
http://home.planet.nl/~Jennit/Techni...0/MyTip013.htm
and
http://home.planet.nl/~Jennit/Techni...1/MyTip100.htm
I found two good write-up regarding this matter, see:
http://home.planet.nl/~Jennit/Techni...0/MyTip013.htm
and
http://home.planet.nl/~Jennit/Techni...1/MyTip100.htm
09-08-2003, 09:56 PM
#34
Drifting
Since the rear axle shafts are about the same diameter as the central shaft, why aren't twisted or broken axles reported?
The maximum torque on my S4 is only 320 ft-lbs; the differential is at a 3:538:1 ratio, so the maximum torque on the axles would be amplified to 1132 ft-lbs.
I've never read a post here from someone breaking a rear axle. How much torque is needed to deform a shaft that size?
The maximum torque on my S4 is only 320 ft-lbs; the differential is at a 3:538:1 ratio, so the maximum torque on the axles would be amplified to 1132 ft-lbs.
I've never read a post here from someone breaking a rear axle. How much torque is needed to deform a shaft that size?
09-09-2003, 11:09 AM
#36
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Earl said:
...............Constantine's sliding coupling could reduce the possibility of TBF much more.
---------
Earl,
Have you seen this clutch and where to find it?
...............Constantine's sliding coupling could reduce the possibility of TBF much more.
---------
Earl,
Have you seen this clutch and where to find it?
09-11-2003, 09:32 AM
#39
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Erik,
I did a search on "constantine" and got hits on a Constantine in the bay area of CA. Either Constantine moved from Florida or there are two Constantines? Constantine does post once in a while, maybe I am spelling his name wrong? I don't know. Maybe he stopped working on the sliding coupling project? I think that he started working on it 3 or 4 years ago, I would think that he would have some results by now.
I did a search on "constantine" and got hits on a Constantine in the bay area of CA. Either Constantine moved from Florida or there are two Constantines? Constantine does post once in a while, maybe I am spelling his name wrong? I don't know. Maybe he stopped working on the sliding coupling project? I think that he started working on it 3 or 4 years ago, I would think that he would have some results by now.
09-16-2003, 11:28 AM
#40
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Earl,
Anyway thanks for your effort
Sorry for late answer, I just return from the 928 EURO meeting in Germany
I drowe alost 2000 Miles, so now I will check my flex-plate again.
Regards from Erik in Denmark
Anyway thanks for your effort
Sorry for late answer, I just return from the 928 EURO meeting in Germany
I drowe alost 2000 Miles, so now I will check my flex-plate again.
Regards from Erik in Denmark
09-22-2003, 08:29 AM
#41
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Earl,
I checked the flex plate - That's OK = No movement - And the drive there was not all 'Sunday School' driving, several times I drove 250 Km/h (155 M)
and the lap on Nuhrburgring with Rich (US) as driver, was much more far from the 'Sunday School'
I still have the 3000 RPM vibration - Saturday I changed the rear joint shaft left and right and greased them - Still the same
Regards from Erik in Denmark
I checked the flex plate - That's OK = No movement - And the drive there was not all 'Sunday School' driving, several times I drove 250 Km/h (155 M)
and the lap on Nuhrburgring with Rich (US) as driver, was much more far from the 'Sunday School'
I still have the 3000 RPM vibration - Saturday I changed the rear joint shaft left and right and greased them - Still the same
Regards from Erik in Denmark
10-04-2003, 08:36 AM
#42
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Important message to all 928 owners with 3000 RPM vibrations
I cured my 3000 RMP vibrations by installing a set of the old (pre 84 model) engine dampers - I.e. I have now new hydraulic engine mounts PLUS the old hydraulic dampers (shocks)
I did as a test today and It works
- The engine is now like 'silk' all the way op
I could do it because I have a 80 and a 84 model, but I had to make new mountings for installing the shocks on the engine (the hydraulic engine mounts take the place of the old shock mountings).
Today is one of the good days
Regards from Erik in Denmark
I cured my 3000 RMP vibrations by installing a set of the old (pre 84 model) engine dampers - I.e. I have now new hydraulic engine mounts PLUS the old hydraulic dampers (shocks)
I did as a test today and It works
- The engine is now like 'silk' all the way op I could do it because I have a 80 and a 84 model, but I had to make new mountings for installing the shocks on the engine (the hydraulic engine mounts take the place of the old shock mountings).
Today is one of the good days
Regards from Erik in Denmark
10-05-2003, 08:26 AM
#43
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Hey,
I made a test-drive again today - The result is great - 90% of the vibration/resonance at 3000 to 3500 RPM are gone and the engine feels more like a turbine all the 'way up' - I tested the car up to 250 Km/h (160 Miles) - The police was not on the highway today!
PS: My engine mounts are new and the original hydraulic type
I made a test-drive again today - The result is great - 90% of the vibration/resonance at 3000 to 3500 RPM are gone and the engine feels more like a turbine all the 'way up' - I tested the car up to 250 Km/h (160 Miles) - The police was not on the highway today!
PS: My engine mounts are new and the original hydraulic type
10-14-2003, 06:48 PM
#44
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OK, it looks like everyone has put in there input. I am still wondering if anyone has an idea of what actually causes the vibration at 3K rpm in the first place? - Ruf
10-14-2003, 07:45 PM
#45
I can tell you what caused the 3k vibration in my '81 5-sp. It was really more a shudder than a vibration. The torque tube was the culprit..... The front bearing migrated toward the rear.
A new torque tube fixed my vibration.
A new torque tube fixed my vibration.