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Discussion Starter #1
I saw a post that a member with a CGTS thought their LSD/PTV was bad. The method he used was with the car in the air turning one wheel. If the other wheel didn't rotate the OP said that the LSD was bad. To test the theory I tried it on my car . My car that also has PTV/LSD and only one wheel turns, the other side does not move . My car is new 600miles no track and works perfectly so i question using the method to diagnose a bad LSD. carl https://www.youtube.com/watch?v=sFTN3ecJsLM&feature=youtu.be
 

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Was the gearbox in neutral? If so, a clutch type LSD typically causes both wheels to rotate together in the same direction (and an open diff usually causes the wheels to rotate in opposite directions).
 

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Was the gearbox in neutral? If so, a clutch type LSD typically causes both wheels to rotate together in the same direction (and an open diff usually causes the wheels to rotate in opposite directions).

i thought that should be in 1st gear for it to rotate towards the front..

Lemon
 

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Discussion Starter #5 (Edited)
Was the gearbox in neutral? If so, a clutch type LSD typically causes both wheels to rotate together in the same direction (and an open diff usually causes the wheels to rotate in opposite directions).
Yes the video was shot in neutral i also tried the other wheel it was the same,only one turns.. Someone with an open diff should try?
I agree thats how they used to work but not now at least not the LSD/PTV on the 981. carl
 

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Do you have PDK or manual? The diff with PDK is hydraulically controlled and may not be active when not driving (only locks in certain conditions and intentionally opens in others)
 

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I've had this discussion about other cars which were specified with an LSD. The other wheel never rotated either.
 

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Interesting- I'm stumped
 

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On the same subject. If you did a hard launch and if the back end slips a little to either side then both tires are spinning. Does that equate to limited slip. Without limited then one would spin but stay straight.
 

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On the same subject. If you did a hard launch and if the back end slips a little to either side then both tires are spinning. Does that equate to limited slip. Without limited then one would spin but stay straight.
Yes, sounds right
 

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On the same subject. If you did a hard launch and if the back end slips a little to either side then both tires are spinning. Does that equate to limited slip. Without limited then one would spin but stay straight.
You should get more sideways motion on an open diff (non LSD)

The sideways motion is relative to the difference in rotation speeds of the back wheels. LSD closer spin rate. Non LSD large spin rate differential.

There is also more gyroscopic torque applied at 90 degrees to the direction of rotation as one wheel is spinning very fast the other not.
 

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Now I wonder if mine is working correctly. But I like the way the car drives and handles so I won't worry too much about it.
 

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I am convinced my PTV/LSD is shot in the 6sp Manual CGTS (after 3K miles), but you guys raise a good point... perhaps PTV does not spin the other wheel while in neutral elevated off the ground. I have the question out to a master Porsche Technician (from Paul Miller). I asked how to diagnose an issue with PTV/LSD in a new P-car with manual trans... will respond when I hear back.
 

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Discussion Starter #15 (Edited)
I am convinced my PTV/LSD is shot in the 6sp Manual CGTS (after 3K miles), but you guys raise a good point... perhaps PTV does not spin the other wheel while in neutral elevated off the ground. I have the question out to a master Porsche Technician (from Paul Miller). I asked how to diagnose an issue with PTV/LSD in a new P-car with manual trans... will respond when I hear back.
Im not sure how the LSD lock up works on the PTV. My car is new (600mi) and the video shows only one wheel turns. So i question if you really have a burned out LSD. Or at least the diagnostic method. carl https://www.youtube.com/watch?v=sFTN...ature=youtu.be
 

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I'm not a Porsche technician but considering the way PTV LSD works in my mind's eye, seems like you freeze a piece of ice large enough for one back tire to park on, add a little water to make it extra slippy, then drive off. If it spins like crazy on the ice, you have a problem, if it slips only a little before torque is transferred to the dry pavement wheel, LSD is working. Both sides should function the same. PTV works through braking the inside tire on turns, not sure how to test it.
 

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Discussion Starter #17
I'm not a Porsche technician but considering the way PTV LSD works in my mind's eye, seems like you freeze a piece of ice large enough for one back tire to park on, add a little water to make it extra slippy, then drive off. If it spins like crazy on the ice, you have a problem, if it slips only a little before torque is transferred to the dry pavement wheel, LSD is working. Both sides should function the same. PTV works through braking the inside tire on turns, not sure how to test it.
The brakes are only one component of the PTV. There is also a mechanical limited slip differential . carl
 

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I'm not a Porsche technician but considering the way PTV LSD works in my mind's eye, seems like you freeze a piece of ice large enough for one back tire to park on, add a little water to make it extra slippy, then drive off. If it spins like crazy on the ice, you have a problem, if it slips only a little before torque is transferred to the dry pavement wheel, LSD is working. Both sides should function the same. PTV works through braking the inside tire on turns, not sure how to test it.
Actually, with a clutch type LSD, the default setting is locked (doesn't spin slightly and then lock). Takes differential torque to unlock...
 

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The brakes are only one component of the PTV. There is also a mechanical limited slip differential . carl
Since PTV is a partial electronic system the opposite wheel will not spin when you spin one wheel by hand with the rear off the ground. I have not been able to get an answer on how to diagnose an LSD problem on the PTV system. The fact that I could put full power down initially and now, I can't put full power down coming out of tight turns is my only clue... Will continue to speak with those more qualified to find an answer... Lou
 

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OK, so bad news from Porsche on diagnosing anD fixing PTV LSD issues/problems:

1) You can't check PTV-LSD operation by spinning the wheels while the car is off the ground like a normal mechanical LSD as PTV is controlled electronically. 2) And even worse, there are NO service procedures or parts available for the PTV/LSD as of yet! Even the Porsche dealer can't fix it if they go bad.

This information came straight from a Porsche Master Technician.
 
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