We need to do a LSD survey - can everyone go out and do a LSD test...
04-06-2009, 10:50 AM
#1
Drifting
Thread Starter
We need to do a LSD survey - can everyone go out and do a LSD test...
- jack up one rear tire with car in neutral and with hand brake off
- try and rotate the wheel
- does it spin (y/n)
- if not, what happens exactly
- i would suspect that anyone who has tracked more than 10 times has a open diff
- i also think that this LSD issue is as big as the RMS but it is far better hidden but needs exposing
- try and rotate the wheel
- does it spin (y/n)
- if not, what happens exactly
- i would suspect that anyone who has tracked more than 10 times has a open diff
- i also think that this LSD issue is as big as the RMS but it is far better hidden but needs exposing
04-06-2009, 10:56 AM
#2
GT3 player par excellence
Lifetime Rennlist
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total of 7 GT3 (both 6 and 7, inc RS), all open diff., and confirmed by dealer. all replaced by dealer except one where i put paul guard unit in (6).
now PLEASE DO NOT DO THIS YOURSELF, I REPEAT DO NOT DO THIS YOURSELF.
this is how the dealer tested my LSD.
car on lift
no one in car, but somehow they engaged the drivetrain such that the rear wheels are turning under power. then this brave soul picks up a piece of 2x6 or 2x8, wedge it under the tire b/n the tire and his shoulder (remember the tires are turning). he was able to hold the piece of wood and stock the moving wheel. they he said, it's completely open diff.
i asked what if it's a working diff. he said the wood would SHOOT out backwards and hurt someone and told me not to do it myself.
this is NOT a joke, i watched him do it. i was told that's the real test. i am just a messenger.
now PLEASE DO NOT DO THIS YOURSELF, I REPEAT DO NOT DO THIS YOURSELF.
this is how the dealer tested my LSD.
car on lift
no one in car, but somehow they engaged the drivetrain such that the rear wheels are turning under power. then this brave soul picks up a piece of 2x6 or 2x8, wedge it under the tire b/n the tire and his shoulder (remember the tires are turning). he was able to hold the piece of wood and stock the moving wheel. they he said, it's completely open diff.
i asked what if it's a working diff. he said the wood would SHOOT out backwards and hurt someone and told me not to do it myself.
this is NOT a joke, i watched him do it. i was told that's the real test. i am just a messenger.
04-06-2009, 11:10 AM
#3
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Well ... this is not a new issue. Low end friction discs have been the norm in street cars since even before the 993 came out.
The proper way to test is: one wheel up, other wheel properly blocked, handbrake off, trans in neutral. Oh ... ENGINE OFF (lol). Grasp the loose tire and turn it. The greater the resistance, the more aggressive (useful for track) the LSD.
The proper way to test is: one wheel up, other wheel properly blocked, handbrake off, trans in neutral. Oh ... ENGINE OFF (lol). Grasp the loose tire and turn it. The greater the resistance, the more aggressive (useful for track) the LSD.
04-06-2009, 11:32 AM
#4
Rennlist Member
- jack up one rear tire with car in neutral and with hand brake off
- try and rotate the wheel
- does it spin (y/n)
- if not, what happens exactly
- i would suspect that anyone who has tracked more than 10 times has a open diff
- i also think that this LSD issue is as big as the RMS but it is far better hidden but needs exposing
- try and rotate the wheel
- does it spin (y/n)
- if not, what happens exactly
- i would suspect that anyone who has tracked more than 10 times has a open diff
- i also think that this LSD issue is as big as the RMS but it is far better hidden but needs exposing
But, Paul, is this the proper test??? When I do the same with car in gear, and both rear wheels in the air, both wheels turn...isn't this the right way to check the LSD? I'm confused...
04-06-2009, 12:16 PM
#5
Rennlist Member
total of 7 GT3 (both 6 and 7, inc RS), all open diff., and confirmed by dealer. all replaced by dealer except one where i put paul guard unit in (6).
now PLEASE DO NOT DO THIS YOURSELF, I REPEAT DO NOT DO THIS YOURSELF.
this is how the dealer tested my LSD.
car on lift
no one in car, but somehow they engaged the drivetrain such that the rear wheels are turning under power. then this brave soul picks up a piece of 2x6 or 2x8, wedge it under the tire b/n the tire and his shoulder (remember the tires are turning). he was able to hold the piece of wood and stock the moving wheel. they he said, it's completely open diff.
i asked what if it's a working diff. he said the wood would SHOOT out backwards and hurt someone and told me not to do it myself.
this is NOT a joke, i watched him do it. i was told that's the real test. i am just a messenger.
now PLEASE DO NOT DO THIS YOURSELF, I REPEAT DO NOT DO THIS YOURSELF.
this is how the dealer tested my LSD.
car on lift
no one in car, but somehow they engaged the drivetrain such that the rear wheels are turning under power. then this brave soul picks up a piece of 2x6 or 2x8, wedge it under the tire b/n the tire and his shoulder (remember the tires are turning). he was able to hold the piece of wood and stock the moving wheel. they he said, it's completely open diff.
i asked what if it's a working diff. he said the wood would SHOOT out backwards and hurt someone and told me not to do it myself.
this is NOT a joke, i watched him do it. i was told that's the real test. i am just a messenger.
Now we are starting to getting somewhere. This makes the most sense to me!!
04-06-2009, 12:42 PM
#6
Drifting
Thread Starter
total of 7 GT3 (both 6 and 7, inc RS), all open diff., and confirmed by dealer. all replaced by dealer except one where i put paul guard unit in (6).
now PLEASE DO NOT DO THIS YOURSELF, I REPEAT DO NOT DO THIS YOURSELF.
this is how the dealer tested my LSD.
car on lift
no one in car, but somehow they engaged the drivetrain such that the rear wheels are turning under power. then this brave soul picks up a piece of 2x6 or 2x8, wedge it under the tire b/n the tire and his shoulder (remember the tires are turning). he was able to hold the piece of wood and stock the moving wheel. they he said, it's completely open diff.
i asked what if it's a working diff. he said the wood would SHOOT out backwards and hurt someone and told me not to do it myself.
this is NOT a joke, i watched him do it. i was told that's the real test. i am just a messenger.
now PLEASE DO NOT DO THIS YOURSELF, I REPEAT DO NOT DO THIS YOURSELF.
this is how the dealer tested my LSD.
car on lift
no one in car, but somehow they engaged the drivetrain such that the rear wheels are turning under power. then this brave soul picks up a piece of 2x6 or 2x8, wedge it under the tire b/n the tire and his shoulder (remember the tires are turning). he was able to hold the piece of wood and stock the moving wheel. they he said, it's completely open diff.
i asked what if it's a working diff. he said the wood would SHOOT out backwards and hurt someone and told me not to do it myself.
this is NOT a joke, i watched him do it. i was told that's the real test. i am just a messenger.
lets put it this way, if your hand can overcome the friction plates in the LSD, there is no way it will be doing anything when you are trail braking a 3100# car plus driver into the busstop at Watkins Glen at 145mph or pick your favorite 50mph 90 degree corner where the inside wheel has less traction (doesn't even need to be in the air)
i would love to see the flying board test done on a Guard Unit though
paul
04-06-2009, 12:44 PM
#7
Rennlist Member
total of 7 GT3 (both 6 and 7, inc RS), all open diff., and confirmed by dealer. all replaced by dealer except one where i put paul guard unit in (6).
now PLEASE DO NOT DO THIS YOURSELF, I REPEAT DO NOT DO THIS YOURSELF.
this is how the dealer tested my LSD.
car on lift
no one in car, but somehow they engaged the drivetrain such that the rear wheels are turning under power. then this brave soul picks up a piece of 2x6 or 2x8, wedge it under the tire b/n the tire and his shoulder (remember the tires are turning). he was able to hold the piece of wood and stock the moving wheel. they he said, it's completely open diff.
i asked what if it's a working diff. he said the wood would SHOOT out backwards and hurt someone and told me not to do it myself.
this is NOT a joke, i watched him do it. i was told that's the real test. i am just a messenger.
now PLEASE DO NOT DO THIS YOURSELF, I REPEAT DO NOT DO THIS YOURSELF.
this is how the dealer tested my LSD.
car on lift
no one in car, but somehow they engaged the drivetrain such that the rear wheels are turning under power. then this brave soul picks up a piece of 2x6 or 2x8, wedge it under the tire b/n the tire and his shoulder (remember the tires are turning). he was able to hold the piece of wood and stock the moving wheel. they he said, it's completely open diff.
i asked what if it's a working diff. he said the wood would SHOOT out backwards and hurt someone and told me not to do it myself.
this is NOT a joke, i watched him do it. i was told that's the real test. i am just a messenger.
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04-06-2009, 01:27 PM
#9
Rennlist Member
I will check this out, but when you jack one tire up, leaving the other on the ground you have to put the car in gear to lock the axle so that you can see how much give there is between the two tires by way of the friction disks. If its not in gear then you are just going to turn the axle I may be wrong will update when I get a reply.
I was wrong this is a email from Joe Reiser who responds to questions on the PCA web
If you take the car out of gear, chock a wheel or two, jack up one side of the back of the car, and turn the raised rear wheel with a torque wrench, how many foot pounds of torque does it take to start turning? Less than 5 like a 996 street GT3 is no good. 150 like a 997 Cup is excessive for a street car. What we want is somewhere in between. 20 to 40 is ideal. You have to go to the center axle nut to get an accurate reading because the other 5 lugs are off-center. But using one of them is probably close enough for this test.
Joel R
I did not put a wrench on it but I could spine mine like a top.
I was wrong this is a email from Joe Reiser who responds to questions on the PCA web
If you take the car out of gear, chock a wheel or two, jack up one side of the back of the car, and turn the raised rear wheel with a torque wrench, how many foot pounds of torque does it take to start turning? Less than 5 like a 996 street GT3 is no good. 150 like a 997 Cup is excessive for a street car. What we want is somewhere in between. 20 to 40 is ideal. You have to go to the center axle nut to get an accurate reading because the other 5 lugs are off-center. But using one of them is probably close enough for this test.
Joel R
I did not put a wrench on it but I could spine mine like a top.
04-06-2009, 05:14 PM
#12
Drifting
Thread Starter
- black marks on the road is not the test to do
04-06-2009, 05:20 PM
#13
Drifting
Thread Starter
- i would think that this is possible but it could also be from a heavy right foot and driving with TC (ON) - but you may be onto something (hard to prove likely)
04-06-2009, 07:54 PM
#14
Rennlist Member
- Excessive rear Brake pad wear is a clear indication of driving with TC on (and forcing the system to operate)
- However, I'm not sure if TC helps the LSD in its job, or makes it work harder? (Working against the brakes?) Opinions? Sure thing is that in LSDless 997s the rear brakes act as an LSD by stopping the inside wheel spinning, but they rob power from the car, instead of applying it like with a proper LSD (that's why a LSD car will still accelerate hard while still going sideways.)
04-06-2009, 07:58 PM
#15
Rennlist Member
The main thing I don't understand is why some people complain about the LSD not working if they drive with TC ON??!!
TC doesn't let the LSD do its full work. Acceleration coming our of a corner at the limit is very different with or without TC (and SC obviously in case of a GT2)