Hey guys I am changing my PDK fluids including the differential on my 991.1 GTS.
I am trying to determine whether my differential is limited slip torque vectoring and if it is it will or should use thedifferential fluid with friction modifiers. If not they just use the GL5 type 75 90W gear oil. Anyone have any clues on this?

Thanks

 

No friction modifier is needed only one type of fluid is used and it is usually Mobilube PTX SAE 75W90 - 00004330549
https://www.pelicanparts.com/More_In...043-305-49-OEM

LiquiMoly, Fuchs, Motul 300 are all good substitutions but there are many more for less ....

 

The differential takes a pretty standard GL5 75w90.

It's generally a safe bet to go with any fluid listed as compatible by a parts shop that specializes in your car. FCP is generally a safe bet, as they tend to hand pick things like fluids, and err on the side of OE and OEM for them. There's also the parts catalogue available from Porsche directly that will list things like fluids and what models/trims they are appropriate for if you fancy that.

In this case, the PDK fluid is different from the differential fluid so make sure you're draining and filling from the correct holes!

 

Yep I understand the different fill ponts and have PWIS if I want to put it in fill mode. Is it my understanding these cars do NOT have a limited slip differential?
If thats true it seems lame and I wonder what the thinking was on that. My cayenne has torque vectoring and has the electronically controlled LSD.
911 is the star of the line up you would thing they would put the LSD on all of them standard.

 

Mechanical limited slips are becoming a thing of the past. Brake vectoring, while sapping a tiny bit of power (exclusively in a situation where you have too much power, keep in mind), offers far more control.

edit - the 991.2 AWD models have an available limited slip rear end, but they still use 75w90 from what I can tell. the 991.1 PDK has a LSD variant as well, remembering from another recent thread about replacing a failed PDK.

 

This is the language in the 2013 brochure:

PTV in conjunction with the manual
gearbox, and PTV Plus with Porsche
Doppelkupplung (PDK), are available
as options for the 911 Carrera and
Carrera 4 models and standard in the
911 Carrera S and 4S models. Both
systems actively enhance vehicle
dynamics and stability. Operating in
conjunction with a mechanical (PTV) or
electronic (PTV Plus) rear differential
lock, they work by braking the rear
wheels as the situation demands.

So the only thing that changes is mechanical vs. electronic locking depending on your transmission. Doesn't look like either is "LSD" by their description. Unless I'm missing something.

 

I did this on my TTS a while back and did a DIY. Not sure if there is a difference between the PDKs.

https://rennlist.com/forums/attachme...nge-diy_lo.pdf

https://rennlist.com/forums/991-turb...l#post17212156

 

Mechanical LSD is getting more difficult to get because the electronic LSD is basically free to your friendly neighbor automaker (its just software).
The sad part is the electronic LSD will wear your brakes (and overheat them if really pushing), reduce power output and simply does not give you the feel that a real LSD does.

 

991.2 Manual (only) GT3 comes with a mechanical LSD.

My 991.2 GTS came with an E-Diff LSD. It was a pile of rubbish that would give up on the track.

This. I hated the E-diff LSD so much, I had it removed and replaced with a proper OS Giken Mechanical LSD.

It has transformed the car. The biggest noticeable change is under heavy braking. The car no longer dances around.
I can brake much harder and the car is just glued to the ground.

I used to chew brake pads like gum. 🤣.

Even running tractional control fully off, the E-Diff still tried to interfere, and as soon as it got hot, it wouldn’t lock.

I even got a “Front Diff Failure” warning light come up on the dash. 🤣. Which is pretty funny as my GTS is RWD.

Zero issues since installing the full Mechanical diff. The car feels more relaxed and calm, and sure footed.

No more panicking nannies giving unwanted and unnecessary input. The car is pure now.

The journo’s constantly write that you can’t feel them intervening. B.S. Its just a better and suoerior car without them. Its like ditching a screaming, panicking passenger.
The car is composed and nothing upsets it anymore.
Its such a pleasure to drive.

Porsche should offer a Nanny free spec. Before all the Karens jump in and claim it would be dangerous, Rubbish!

Guns don’t kill people, people kill people.

The lack of nannies don’t cause crashes, lack of peoples control does.

Chomping a heap of rear brake unexpectedly, will not save you at the track. My 02c.

 

Great post and comments, would be great to know more about what you did here. My 991.1S is fun but I agree with your thoughts after tracking it more and comparing it to my turbo with a Cup LSD.
The stability under heavy braking you spoke of along with later turn-in/trail braking a well set up diff provide are undervalued by a lot IMO. What options did you consider, if any for a diff, cost, etc. would be great - thx

 

Just curious, what mileage did you have on the TTS when you performed the fluid changes?

 

Can't remember exactly but roughly between 55-60k. I was approaching the major 60k service.

 

Im at 40K, maybe at 60K feel around how to service,,if needed, most likely dealer

 

There weren’t any options. It was assumed the OS Giken would fit, but it was not direct bolt on. It had to be modified.

Details on my mod thread. I think it ended up around $7k AUD.

 

Interesting info on mechanical LSD vs E-Diff.
l seen on many occasions comments on the GT3 PDK E-Diff outperforms the manual one. Puts power down much better including more stability.