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Factory or aftermarket, a LSD performs best with a gear oil designed for that application. This is usually due to certain additives that work with the friction plates.
Suggest if it's original and you have the trans out, may want to check the friction plates for wear/replacement.
I would source the approved list of oils from Porsche. It is rather lengthy although there are other great products they haven't tested that meet the requirements set out by Porsche. The redline ns is fine but you will need to add about 6 oz's or more of their friction modifier or you can use their LSD specific oils. I have used Driven recently and it has quieted down my 100% locking diff on my turbo which are notorious for making noises at low speeds. If you think The dealerships use the oils noted on the stickers of our cars you are mistaken. Most dealerships buy in Bulk from the cheapest source so long as it is on the approved list. You could use the factory oils at $30+ a Liter but even most dealerships don't use it.
I can't locate it but it is like this for trans fluid
Another change in topic that I don't understand.
Back to transmission oils
friction modifiers reduce the effectiveness of a lsd, if that's what you want fine, Prime example is Cobalt's 0/100 which can b a bitch to deal w/
the 25/65 used in base 993s isn't all that effective or intrusive to begin w/ and the stock friction plates wear quickly. It soon becomes a defacto open diff. Do you really want to further reduce it's effectiveness?
For Motor sports use Mobil 1 Delvac is the go to transoil, no modifiers needed, This oil may not be best for street use due to it's cold characteristics which make it stiff and notchy for the first few miles.
There a re plenty of good SAE 75w-90 GL5 oils available from
M1, Motul, Castrol et al
The only two approved fluids per Porsche (see attached) are the Mobilube PTX and the Shell which is apparently their Spirax S5 ATE 75W-90 which is made in Switzerland. The new Classic Gearbox oil appears to be the Shell Spirax S5 ATE 75W-90 as it has exactly the same viscosity and is also made in Switzerland. While at Luft, the Porsche Classic Representative had confirmed this as well. In my two G50's I was using the Redline 75W-90NS wo issue. My plan is to change to the PTX (have that fluid on hand) in the 1988 and the Porsche Classic was installed in the 993C4S (purchased from Sunset). As for pricing, the Classic is actually cheaper than the PTX and both are available through Sunset. DELVAC is NOT PTX! While many have used with apparent success its not the same and Mobil's PTX sales sheet say's that PTX is specifically designed for Porsche Transaxles. Sad that Porsche,Mobil and Shell made obtaining the correct fluid so difficult in the US!
The only two approved fluids per Porsche (see attached) are the Mobilube PTX and the Shell which is apparently their Spirax S5 ATE 75W-90 which is made in Switzerland. The new Classic Gearbox oil appears to be the Shell Spirax S5 ATE 75W-90 as it has exactly the same viscosity and is also made in Switzerland. While at Luft, the Porsche Classic Representative had confirmed this as well. In my two G50's I was using the Redline 75W-90NS wo issue. My plan is to change to the PTX (have that fluid on hand) in the 1988 and the Porsche Classic was installed in the 993C4S (purchased from Sunset). As for pricing, the Classic is actually cheaper than the PTX and both are available through Sunset. DELVAC is NOT PTX! While many have used with apparent success its not the same and Mobil's PTX sales sheet say's that PTX is specifically designed for Porsche Transaxles. Sad that Porsche,Mobil and Shell made obtaining the correct fluid so difficult in the US!
No PTX is not Delvac and thank god for that
Delvac is and has been for decades THE factory Motorsports fill
As I said lots of good GL5 street fills out here, and just because it's not on THE list doesn't mean a thing
The pre '87 trans fill needed a different oil because of the Porsche specific synchro design used in them, for these trans a a non synthetic GL5 fluid is needed, the beast being SWEPCO, which is not on THE list either but was used by the factory race teams of the era.
Delvac for G50 track use PTX, M1 , Shell whatever GL5 for the street, and SWEPCO 201 for 901, 911 & 915 use both street and track, alternately 202 or 210 for more extreme use
Last edited by Bill Verburg; 11-14-2023 at 03:26 PM.
I think there's later information. 75W-80 is not the preferred fill. Porsche Classic Gearbox Oil PCG 043 210 52 is 75W-90 GL-5 and approved for 993 as well as all Porsche 911's through 996. It says so right on the can.
11-13-2023, 01:31 PM
