Who runs LSD's?
11-19-2017, 08:41 PM
#16
Rennlist Member
Sorry, no driving experience with a LSD or TBD on the 997. However, I do have a Quaife TBD on the way. I got a great deal on it, otherwise I would have probably gone for a OS Giken Superlock. Guards seem to be pretty much the unanimous choice for any super serious Track drivers, who want the benefit of the LSD during decelleration, as well as accelleration.
I read for hours and hours on this topic just the other night. I by no means an expert, but this is a recap of the pros and cons of each, from what I read...
Quaife and Wavetrac (TBD, not LSD) (Guard also used to make a TBD, but discontinued it due to low sales)
Pro - less expensive, low maintenance, doesnt impede PASM (if you choose to leave enabled,) does not cause any additional understeer, ideal for street and autocross
Con - lockup on accelleration only (Wavetrac says they have decel lockup, but I havent seen any proof it works,) may fail under hard-core race conditons, if one rear wheel lifts and has zero traction, then it will act as an open diff
OS Giken Superlock
Pro - mid priced, low maintenance, offers the benefits of LSD (Accel and decel lockup) without the drawbacks (understeer)
Con - not proven reliability at the same level of Guards, had a bunch of failures due to a bad batches for other cars a few years back (not Porsche) that damaged people cars. These were addressed, but from what I was reading, the resulting damage to peoples cars was not reimbursed, only the warrantied parts replaced
Guard
Pro - The overwhelming choice for those running at the higher levels on the track. Most reliable under extreme conditions
Con - a bit of mid-corner understeer (that apparently is something you get used to in a short time,) expensive to buy and maintain
OEM on GT3 and Carrera (different diffs, but share the same PRO/CONS)
Pro - works well when new
Con - stops working very quickly. Reports that it no longer works as intending, and acts as an open diff, after just a few track days.
I read for hours and hours on this topic just the other night. I by no means an expert, but this is a recap of the pros and cons of each, from what I read...
Quaife and Wavetrac (TBD, not LSD) (Guard also used to make a TBD, but discontinued it due to low sales)
Pro - less expensive, low maintenance, doesnt impede PASM (if you choose to leave enabled,) does not cause any additional understeer, ideal for street and autocross
Con - lockup on accelleration only (Wavetrac says they have decel lockup, but I havent seen any proof it works,) may fail under hard-core race conditons, if one rear wheel lifts and has zero traction, then it will act as an open diff
OS Giken Superlock
Pro - mid priced, low maintenance, offers the benefits of LSD (Accel and decel lockup) without the drawbacks (understeer)
Con - not proven reliability at the same level of Guards, had a bunch of failures due to a bad batches for other cars a few years back (not Porsche) that damaged people cars. These were addressed, but from what I was reading, the resulting damage to peoples cars was not reimbursed, only the warrantied parts replaced
Guard
Pro - The overwhelming choice for those running at the higher levels on the track. Most reliable under extreme conditions
Con - a bit of mid-corner understeer (that apparently is something you get used to in a short time,) expensive to buy and maintain
OEM on GT3 and Carrera (different diffs, but share the same PRO/CONS)
Pro - works well when new
Con - stops working very quickly. Reports that it no longer works as intending, and acts as an open diff, after just a few track days.
Last edited by halo777; 11-19-2017 at 09:56 PM.
11-19-2017, 09:59 PM
#17
Rennlist Member
Read this. comment #16..
https://rennlist.com/forums/997-foru...l#post13981436
https://rennlist.com/forums/997-foru...l#post13981436
A couple of comments in no particular order and without quoting anyone, so I am sure I will miss something...
The 997 Carreras use an Aisin gearbox that is quite different than the Getrag box in the GT3s and 996 Turbos. In my experience the factory LSD in the Aisins is actually a pretty robust and durable and well functioning LSD. This is in direct contrast to the GT3 LSD which has crap clutches and works poorly from day one.
I only have the aftersales manual for the 997 and it does not show the test for the LSD. I apologise for no knowing the breakaway test number, but suspect it is found in the tranny module on the complete 997 FSM. One cannot use the GT3 numbers for this LSD.
It is a low preload unit and spinning the wheels doesn't reveal much because it doesn't go active without a pretty good slip event (load) on it. It also will not provide the same rear end under braking stability that a motorsports LSD does because it lacks that preload. This point is important.
My inclination is that it isn't so much that your LSD is worn out as your racecraft has progressed to the point where you are braking harder and later and revealing the performance weakness on the LSD. The unfortunate thing is we don't have a fix for you like we do for the GT3s. We rebuild GT3s. So few Carreras got LSDs is was never cost effective to make parts for them. We only manufacture a new LSD for it.
Lastly, Giken is not a gear driven diff. It is a clutch type LSD. Quaife and Wavetrac make the gear driven torsen gleason designs differentials (we make one too, in addition to our LSD).
All of that said, if you can get a brand new Aisin LSD under your warranty, I have no doubt you will see an improvement in performance. You have a lot of track miles on your unit and it is probably tired. Is it to blame for the wiggle? Not really a definitive answer there, but overall a new LSD at this point in your vehicle's life would benefit your track performance. That piece of it I am confident of...
The 997 Carreras use an Aisin gearbox that is quite different than the Getrag box in the GT3s and 996 Turbos. In my experience the factory LSD in the Aisins is actually a pretty robust and durable and well functioning LSD. This is in direct contrast to the GT3 LSD which has crap clutches and works poorly from day one.
I only have the aftersales manual for the 997 and it does not show the test for the LSD. I apologise for no knowing the breakaway test number, but suspect it is found in the tranny module on the complete 997 FSM. One cannot use the GT3 numbers for this LSD.
It is a low preload unit and spinning the wheels doesn't reveal much because it doesn't go active without a pretty good slip event (load) on it. It also will not provide the same rear end under braking stability that a motorsports LSD does because it lacks that preload. This point is important.
My inclination is that it isn't so much that your LSD is worn out as your racecraft has progressed to the point where you are braking harder and later and revealing the performance weakness on the LSD. The unfortunate thing is we don't have a fix for you like we do for the GT3s. We rebuild GT3s. So few Carreras got LSDs is was never cost effective to make parts for them. We only manufacture a new LSD for it.
Lastly, Giken is not a gear driven diff. It is a clutch type LSD. Quaife and Wavetrac make the gear driven torsen gleason designs differentials (we make one too, in addition to our LSD).
All of that said, if you can get a brand new Aisin LSD under your warranty, I have no doubt you will see an improvement in performance. You have a lot of track miles on your unit and it is probably tired. Is it to blame for the wiggle? Not really a definitive answer there, but overall a new LSD at this point in your vehicle's life would benefit your track performance. That piece of it I am confident of...
11-20-2017, 08:05 PM
#18
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I've driven a couple of air cooled 911s an 88 and a 92 with LSD and loved how you can have a little fun with the rear when having that option, my 95 968 also has that, wish my 997.1S launch edition had it as well..was just wondering about that option couple of days ago.
11-21-2017, 12:58 AM
#19
Instructor
I have a Guard LSD on my GTS. Porsche uses electronics and braking to simulate an LSD on the road but it can not handle the track and causes the traction control to kick in prematurely. You will notice the LSD under braking (more stable) and the speed you carry through corners. The car is "tricked" into thinking that the wheel are not slipping so your TC does not kick in as much. Its a great md and they make one for manual and PDK. Cheers!
11-21-2017, 08:54 AM
#20
Porsche uses electronics and braking to simulate an LSD on the road
