Hi all,

Sorry if this is a dumb question. My research so far has led me to the conclusion that the correct (and best) transmission fluid to use for a 718 GTS 4.0 manual transmission is Mobil 1 Mobilube PTX 75W-90. I.e. this one:
https://www.suncoastparts.com/product/00004320420L.html
I thought Porsche actually filled their cars from factory with this. However, there is also a Porsche branded one, which some service centres say they use:
https://www.suncoastparts.com/product/99991754600.html

Does anyone know what is in the Porsche branded one? What is the difference and which is best?

Many thanks.

 

I use Mobil 1 DELVEAC.

 

@DC021 - 75W-90 Mobil 1 Delveac is what you use for your '20 GT4 manual? How many quarts/liters is the capacity for the trans axle? I have seen DIY's for the 986/987 but never a formal DIY for the 718 manual transmission with 4.0 liter engine. Seems easy enough and I have done this before on other euro cars. Thanks in advance!!!

 

The process is simply enough, drain hole at the bottom, fill on the drivers’s side of the transmission iirc. It took a hair under 4qts.

 

What is the change interval on the 718 4.0? On the 991 and 992 GT3 Manuals, it's 96,000 miles (not affected by track miles like engine oil change interval). Sounds like you were being very proactive (maybe unnecessarily?)...

 

Per my manual it is every 120k miles or 12 years. Assuming it is proactive given lots of track days. Just like changing oil more because of track usage.

 

Gotcha. Did your car come with a Manual for Race Track use? Mine did (GT3) and it shows all the things that have accelerated maintenance requirements when used on the track (engine oil changes 4 times as frequently, for example), but there is no such recommendation for the gear oil...

 

GTS 4.0 did not come with accelerated track use guide. I think the GT4 did (I could be wrong, GT4 owners chime in) so I can use that.

Personally I use common sense and how hard I have driven as the guide of when to change, especially for fluids that Porsche says should be in my car for 12 years. I will be changing my trans axle fluid much sooner than 12 years or 120k. Especially if I do more track days.

But yes, I would love to know the specific gear oil that should be used. The suncoasat link or the Delveac one mentioned above.

 

I understand the impulse to change the gear oil when you've been using the car hard. But, I am trying to understand if there really is any need or benefit to do so (or if it's purely a placebo effect to make us feel better). Since there are no combustion byproducts that dilute the oil (as in the engine), maybe the only limitation we are up against is time (the oil times out after 12 years and it makes no difference if or how much the car is driven hard).

Aside from the shearing and heat that could be experienced, I always wonder if clutch material from the wearing of the LSD would be suspended in the gear oil and could affect lubrication).

If any of these issues was relevant, I guess I would expect that Porsche would indicate a shorter oil service life when tracked...

 

Believe the OP is attempting to alleviate some of his transmission concerns.

 

I hear you - when I change any fluid I usually send into Blackstone for an analysis then I can dial in frequency based upon how the oil "wore". The age old debate .
For example - I have an S4 tuned and I changed the rear diff oil at 35k. The oil analysis came back clean as heck. It was never tracked but very spirited driving. I know I can go more than 35k going forward.
I posted a 4 liter break in oil analysis from Blackstone at 1k or so miles (I drove the car hard for break after 100 miles) and the oil analysis came back clean.

Totally understand what is needed and what makes us feel better . I try to get some data behind it so I can adjust my frequencies for what is needed and good hygiene for the car.

 

Yes. I’ve had a thread on my stiff shift symptom going for a while now. Some good responses which I appreciate, but dealer seems to think there’s nothing wrong so won’t investigate. I thought a transmission fluid change would be something easy to try to see what difference it makes. Could then least analyse the oil for debris.

I’m determined to slowly but surely get to the bottom of it!

Hence the desire to know what Porsche puts into their own branded transmission fluid bottles. I’d like to control all variables when trying to diagnose this issue.

 

GT4 track use guide makes no mention of gear oil: https://www.dropbox.com/s/gifj35gtdq...rcuit.pdf?dl=0

 

I emailed getporscheparts and they said this was the fluid that should be used. Keep in mind this is Porsche OEM oil. I don't know if this solves any issues for aftermarket oil but at least gives you an option.

000-043-305-49 $30.82/Liter

 

Thanks for this. This is the one they used in the end to do my gear oil change. Slight improvement in shift feel (very slight - possibly placebo), but transmission issues still remain for me. No noticeable debris coming out either. I’ll give it some more miles and see how the feel evolves before I try anything else I think.

I don’t know about others but my shift feel is still evolving after 9k miles. It started off super slick and sweet, then became stiffer and bit crunchy. It may have possibly loosened up a bit now, but it still clunks through the synchro teeth rather than slipping in effortlessly like it used to (especially noticeable from second into third).