Transmission fluid for 986 5 speed - redline?

[JFP in PA]

Originally Posted by casioqv

Any idea why Porsche would use such a custom fluid when they're just using a VW/Audi transmission that itself has a spec (VW/Audi G 052 911) that is widely matched by a lot of products?

I'd imagine maybe they are trying to tune the 'feel' of the transmission engagement for performance driving in a way VW wouldn't care about?

Still, it makes me doubt that using a VW/Audi spec oil will cause premature transmission failure.

Honestly, I didn't know all of this when I bought the MT-90. Likely I will change back to the Porsche fluid if I change it again, but in the mean time there are much more pressing maintenance issues on this 22 year old car... and I am satisfied that the MT-90 isn't likely to cause transmission failure.

A retired Porsche engineer told me it is because the transmission used in the Boxster has synchro rings made from an unusual alloy that are not used in the gear box when it is in other applications. We have seen similar unique oils used in other applications for similar reasons; the one that comes to mind is the 5-speed used in late 1990's Nissan Maximas, it required a different oil than all other Nissan applications.

[casioqv]

Originally Posted by JFP in PA

A retired Porsche engineer told me it is because the transmission used in the Boxster has synchro rings made from an unusual alloy

If true that makes a lot of sense. Damn, I guess I'm changing the fluid again after all. I will be more skeptical of what I read in 101 projects from now on...

[JFP in PA]

Originally Posted by casioqv

If true that makes a lot of sense. Damn, I guess I'm changing the fluid again after all. I will be more skeptical of what I read in 101 projects from now on...

Over the years, Wayne published several "sub optimal" ideas, such as using set screws to secure the IMS shaft while doing a retrofit; not everything was off kilter, but some were real doozies............

[DreamSign]

I just (today) went to my local Porsche dealer and bought 3 liters of the 'special' gear oil. It was $35.74 per liter

The price is so close to everything else, it seemed there was really no benefit to trying anything else.

[jaykay]

I promised to report back on Miller from another for thread I believe. I do find it a bit notchy. I am working with a six speed which is well seems to be inherently notchy anyway I'll go back to the Porsche fluid at some point and report back. Just wondering if there's a difference in formulation for the six speed versus five speed

Miller was put in as a substitute for the Porsche fluid without my knowledge or without my consent

[JFP in PA]

Originally Posted by jaykay

Just wondering if there's a difference in formulation for the six speed versus five speed

Yes, the five-speed oil is unique to that transmission, and only when it is in a Porsche because Porsche used some custom alloy in the synchro rings that were not used in the same gear box in other applications like Audi.

[jaykay]

Okay, is there more freedom with the six speed or is strictly another dedicated oil from Porsche? I think I have come across something pertaining to Mobil Delvac being superior…but may have this muddled