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eabeukes
Silverstone


Joined: 30 Jan 2018
Posts: 117


1999 Porsche 996 Carrera 2

PostPosted: Mon Oct 22, 2018 4:11 pm    Post subject: How do I know my LSD still works? Reply with quote

I have an early C2 that came with a LSD - is there any test I can do (other than driving fast sideways) that will tell me if it still works? I don't know if its ever been replaced, but I know the old 'spin one wheel and the other should spin' test might not work on some of the newer systems? eh!
 
  
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stucart
Nürburgring


Joined: 24 Apr 2013
Posts: 493
Location: staffordshire 07 997 C4S


PostPosted: Mon Oct 22, 2018 4:37 pm    Post subject: Reply with quote

Be interested to hear answer to this, never quite understood these?
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Now - Jaguar F-Type 2014 3.0 S Quickshift ,White/ Red interior (theme here!) Loving it .
Previously - 997 C4S Tip-S, 2007, Silver/Red and Black Leather, PSE, Sports Chrono, Turbo wheels.
 
  
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FZP
Magny-Cours


Joined: 18 Jan 2015
Posts: 2564
Location: Cheshire


PostPosted: Mon Oct 22, 2018 4:58 pm    Post subject: Reply with quote

Jack the car in the air with both rear wheels. Spin a wheel. If the on other side spins in the same direction, then it works.
If it spins in the opp direction, it doesn't.
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Last edited by FZP on Mon Oct 22, 2018 5:29 pm; edited 1 time in total
 
  
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infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 7859
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Mon Oct 22, 2018 5:00 pm    Post subject: Reply with quote

The basic test is to jack the rear of the car up and spin a wheel by hand, if they spin together the LSD is still working but I don't think this definite.

I started a thread a while ago as I wanted some more info about the LSD I had, it built into quite an informative thread.

http://911uk.com/viewtopic.php?t=101673
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rigsby99
Monza


Joined: 22 Oct 2015
Posts: 164
Location: South Cheshire


PostPosted: Mon Oct 22, 2018 5:08 pm    Post subject: Reply with quote

You could also put the car on a grass surface and accelerate (gently) and check that both wheels are driving from the marks on the grass.
 
  
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alex yates
Brands Hatch
Brands Hatch


Joined: 06 Mar 2014
Posts: 14270
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Mon Oct 22, 2018 5:13 pm    Post subject: Reply with quote

Surely an LSD can only be tested at speed/load? Similar to a viscous coupling I would've thought.
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Martin996RSR
Spa-Francorchamps


Joined: 08 Dec 2016
Posts: 270



PostPosted: Mon Oct 22, 2018 6:50 pm    Post subject: Reply with quote

Mine is pretty worn but I can still feel it working, both when drifting, and when in tighter low speed corners where I can feel the car rotating into the corner in a way that non-LSD cars just don't do.

As has already been mentioned, to check the LSd was still there and the clutch plates in it hadn't already worn away completely I would go somewhere with a loose surface and see if I made No. 11s or No.1s.
 
  
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kurlykris
Watkins Glen


Joined: 30 Jun 2014
Posts: 2201
Location: Warwickshire


PostPosted: Mon Oct 22, 2018 8:39 pm    Post subject: Reply with quote

On a recent edition of Fifth Gear, the beardy presenter fitted an LSD to an old hot hatch, they did a before and after "test" by basically doing a standing start with a bit of wheelspin on a low traction surface ( painted garage floor ), then measuring the rubber laid down. with no LSD one rubber mark was twice as long as the other, with the LSD fitted the two rubber marks were the same length Grin

Find yourself a nice empty carpark with rubbish tarmac and lay some rubber down Laughing
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2006 Boxster S sport chrono
2010 Mercedes E350 AMG Sport

 
  
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cvega
Monza


Joined: 25 Feb 2013
Posts: 157



PostPosted: Mon Oct 22, 2018 9:09 pm    Post subject: Reply with quote

the "car up in the air, spin wheel" procedure surely only works with a gear/torsen LSD, not with a clutch-plated one that's designed to lock only under load?
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asterix_the_gaul
Suzuka


Joined: 20 Dec 2008
Posts: 1100
Location: Cheshire

1999 Porsche 996 Carrera 2

PostPosted: Mon Oct 22, 2018 9:25 pm    Post subject: Reply with quote

Do all 996 have LSD or was it an option?
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infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 7859
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Mon Oct 22, 2018 9:28 pm    Post subject: Reply with quote

asterix_the_gaul wrote:
Do all 996 have LSD or was it an option?


It was an option on the early cars and wasn't required on the later PSM cars
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kurlykris
Watkins Glen


Joined: 30 Jun 2014
Posts: 2201
Location: Warwickshire


PostPosted: Mon Oct 22, 2018 9:32 pm    Post subject: Reply with quote

asterix_the_gaul wrote:
Do all 996 have LSD or was it an option?


Mine has the option code "224 Limited Slip Diff" Thumb
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2006 Boxster S sport chrono
2010 Mercedes E350 AMG Sport

 
  
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alex yates
Brands Hatch
Brands Hatch


Joined: 06 Mar 2014
Posts: 14270
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Mon Oct 22, 2018 9:33 pm    Post subject: Reply with quote

infrasilver wrote:
asterix_the_gaul wrote:
Do all 996 have LSD or was it an option?


It was an option on the early cars and wasn't required on the later PSM cars


I think it was more a case of they couldn't get the PSM intelligent enough to understand what the car was doing when the LSD was 'working'. The PSM would try and override what the LSD was trying to do by applying brakes, adjusting throttle, etc.

The same issue also happens with the 996 C4. When the rears spin, the PSM drops the throttle before there's enough torque to get the VC working.

They overcame this later hence LSDs being fitted to later cars.
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kurlykris
Watkins Glen


Joined: 30 Jun 2014
Posts: 2201
Location: Warwickshire


PostPosted: Mon Oct 22, 2018 9:35 pm    Post subject: Reply with quote

I just know that I`m going to have to test my LSD at the weekend now PC

You lot are a bad influence Hand
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2010 Mercedes E350 AMG Sport

 
  
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edge
Nürburgring


Joined: 25 Mar 2008
Posts: 438
Location: Devon


PostPosted: Mon Oct 22, 2018 10:06 pm    Post subject: Reply with quote

Doesn't appear to be a massive amount online about the diff type that Porsche fits to there sports cars but if I recall correctly the diff I ordered for my 981 was described as a mechanical diff ( clutch) and my understanding is that this replaced the early type of diff (Viscous) . Not sure if jacking the car and rotating one wheel to see if the other rotates in the same direction will work as I think that both the diff types that Porsche use only come into affect if one of the drive wheels loses traction when under power.

I am probably wrong but as I say not to much info around.
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Peter B
Nürburgring


Joined: 18 Aug 2003
Posts: 465
Location: United Kingdom


PostPosted: Tue Oct 23, 2018 9:47 am    Post subject: Reply with quote

I had an "S" reg late 98 but 99 C2 that was a limited edition "Lux" model fitted with full dark grey leather and an LSD.
Used to leave 50' parallel black stripes.
Just lovely....
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coullstar
Barcelona


Joined: 15 Sep 2015
Posts: 1252
Location: Aberdeen/Torphins


PostPosted: Tue Oct 23, 2018 10:12 am    Post subject: Reply with quote

edge wrote:
Doesn't appear to be a massive amount online about the diff type that Porsche fits to there sports cars but if I recall correctly the diff I ordered for my 981 was described as a mechanical diff ( clutch) and my understanding is that this replaced the early type of diff (Viscous) . Not sure if jacking the car and rotating one wheel to see if the other rotates in the same direction will work as I think that both the diff types that Porsche use only come into affect if one of the drive wheels loses traction when under power.

I am probably wrong but as I say not to much info around.


Clutch style LSD for early cars, the viscous diff was for the 4wd ones at the front.
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eabeukes
Silverstone


Joined: 30 Jan 2018
Posts: 117


1999 Porsche 996 Carrera 2

PostPosted: Tue Oct 23, 2018 10:15 am    Post subject: Reply with quote

infrasilver wrote:
The basic test is to jack the rear of the car up and spin a wheel by hand, if they spin together the LSD is still working but I don't think this definite.


According to the thread you linked ( Thumb thank you, excellent resources in there!) and the research Ive done, the 996 LSD in the older cars will only work under load. The jack-test doesnt load the system and therefore gives you no way to know if its working.


infrasilver wrote:

http://911uk.com/viewtopic.php?t=101673

Mechanic

I'm off to attempt some 11'ses
https://www.youtube.com/watch?v=UZ9hggHF5VU
 
  
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infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 7859
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Tue Oct 23, 2018 3:44 pm    Post subject: Reply with quote

So in the name of Science I tracked down a private test track with smooth tarmac surface that was slightly dusty and laid down some rubber. Grin

Had to filter the picture a little to bring out the black lines.



The shorter lines at the start are with PSM on and the much longer lines are with PSM off, I also have an LSD fitted which is supposed to confuse the PSM but it all seemed to work out fine.



It would have just kept laying rubber but as it started to get a little sideways and the road turns rough with pot holes, I backed out.

Ideally we could do with comparing a non LSD PSM car in similar conditions to compare with the above.
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edge
Nürburgring


Joined: 25 Mar 2008
Posts: 438
Location: Devon


PostPosted: Tue Oct 23, 2018 3:50 pm    Post subject: Reply with quote

Top man infrasilver that's the best way to prove if your LSD works 👌
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