Originally Posted by Mike in CA

Just to clarify, I wasn't referring to just the previous GT cars nor was I singling out the GT4 re: the mechanical LSD. It's just a fact that they've been a known weak point in Porsches for many years. I'm hoping the electronic LSD in the GT3 will fare better in the long run.

Originally Posted by Mike in CA

Just to clarify, I wasn't referring to just the previous GT cars nor was I singling out the GT4 re: the mechanical LSD. It's just a fact that they've been a known weak point in Porsches for many years. I'm hoping the electronic LSD in the GT3 will fare better in the long run.

Originally Posted by Manifold

In the GT3, the e-diff and shocks are two clever items which are essential to the performance of the car, and could be expensive to replace when worn. I hope there proves to be some good way of detecting the progression of their wear, other than realizing one day that the car isn't performing like it used to, but not knowing why.

Originally Posted by GrantG

Fair enough. I would expect that the LSD in the GT4 could/would be beefier than that used in other non-Motorsports versions of the Boxster/Cayman. But, impossible to know at this point without more info.

Originally Posted by doubleurx

Do the standard versions have a LSD, or are they open diffs?

Originally Posted by doubleurx

Do the standard versions have a LSD, or are they open diffs?

Originally Posted by GrantG

Hi Eduardo - I think there was some confusion. Someone was saying that the mechanical LSD in the old 997 GT3 was "dodgy" and they were indeed known to be a bit fragile...AFAIK, the GT4 transmission is very similar/same to that used in current and recent Boxsters/Caymans.

Originally Posted by Mike in CA

Just to clarify, I wasn't referring to just the previous GT cars nor was I singling out the GT4 re: the mechanical LSD. It's just a fact that they've been a known weak point in Porsches for many years. I'm hoping the electronic LSD in the GT3 will fare better in the long run.

Originally Posted by sunnyr

My money is on the GT4 having whatever diff is on PTV equipped 991/981 cars and not what is on 997 GT cars (unless Porsche carried that over for all PTV 991/981 cars).

Originally Posted by sunnyr

And separate question, doesn't GT3 (and other PTV plus cars) also have a mech LSD, except the locking ratio is variable instead of being fixed?

Originally Posted by Manifold

In the GT3, the e-diff and shocks are two clever items which are essential to the performance of the car, and could be expensive to replace when worn. I hope there proves to be some good way of detecting the progression of their wear, other than realizing one day that the car isn't performing like it used to, but not knowing why.

Originally Posted by GrantG

Fair enough. I would expect that the LSD in the GT4 could/would be beefier than that used in other non-Motorsports versions of the Boxster/Cayman. But, impossible to know at this point without more info.

Originally Posted by doubleurx

Do the standard versions have a LSD, or are they open diffs?

Originally Posted by GrantG

It's an option. Mechanical LSD (PTV) with manual gearbox or Electronically controlled LSD with PDK (PTV Plus).

Originally Posted by vantage

Open as standard, PTV (LSD + torque vectoring) optional.

Originally Posted by GTgears

Hi Guys,

Eduardo pinged me and asked me to pop in and shed some light on this. Let's start with a picture since everyone likes pictures. And then I will explain.


This is a picture of the LSD found in the 991 GT3. It is called PTV+. PTV is used in the other vehicles. PTV+ is only used in the 991 GT3, the Turbo and the Carrera S. What you are looking at is how the LSD is actuated to provide variable locking rates in real time. That double row ring with bearings is to distribute the load when force is applied from the outside. The pin he's putting back in the LSD body is what the ring presses down on to apply more force to the clutches, and thus more locking factor.

There is an oil pressure feed that clamps the rings. When the car detects wheelslip the ring is pressurized. It is truly a zero preload LSD with 0% lock in steady state.

Porsche first used this approach back on the 959 and 964 C4 gearboxes. Back then there were slave cylinders applying the force though. This is the next wave in high tech LSDs. At this point we see zero reason to attempt to do better.

The only other thing I would add is that PTV is also a mechanical LSD in conjunction with electronic babysitters. Our LSD will replace that one with a more aggressive unit for owners of 991 Carreras.

Originally Posted by Z356

Yes, PTV+ of the GT3 will fare much better...according to Matt Monson of Guard Transmission LLC. See his post at the end!

Saludos,
Eduardo
Carmel

Originally Posted by Phokaioglaukos

FYI, the mechanical LSD in my street 996 GT3 was weak also. Copans could rebuild it with beefier components (steel instead of brass).

Originally Posted by hf1

Don't mean to derail, but how do I know that my LSD is shot and it needs a rebuild? I need to check the PO records but I think my (996 gt3) LSD is still the original one from new. Can't imagine this car being any more fun at the track than it already is (with a presumably shot LSD).

Originally Posted by BGB Motorsports

OT: Quick and dirty fix...warm up the car, jack up one side, and put a torque wrench on your axle note and use the torque wrench to find out how much force is required to slip the unloaded wheel. If it's not 55 lb/ft or better, she is freed up.

Originally Posted by hf1

Good to know, John. Thx!

Originally Posted by BGB Motorsports

OT: Quick and dirty fix...warm up the car, jack up one side, and put a torque wrench on your axle note and use the torque wrench to find out how much force is required to slip the unloaded wheel. If it's not 55 lb/ft or better, she is freed up.