915 Transmisssion Fluid

[ROW911SC]

Its time for a trans./gear oil change and after reading through several posts here and checking the owner's manual, I see that an SAE 90, GL-5 Dino oil is recommended. Now as it happens my Alfa GTV-6 also requires an 80W 90, GL-5 non-synthetic oil, specifically Shell Spirax HD. Since its almost impossible to get that oil without ordering a case, I'm wondering whether I can use the Shell in my 911 in which case ordering a dozen is cost effective? The car has LS, so would an additive be necessary?

Just wanted to run this by everyone. TIA.

[DRACO A5OG]

Yes, you need LSD additive as far as the gear lube, if it is proper spec dino lube I see why not but others with more experience will hopefully chime in.

Only question, is 81's use single weight 90? hmm seems a little too thick, no?

[RedCoupe]

If the Alfa has an open diff and the Porsche is limited slip, you're not going to be using the same gear oil. I'm not sure why you couldn't use a different high quality GL-5 gear oil in the Alfa that you can buy in smaller quantities.

[ROW911SC]

Originally Posted by RedCoupe

If the Alfa has an open diff and the Porsche is limited slip, you're not going to be using the same gear oil. I'm not sure why you couldn't use a different high quality GL-5 gear oil in the Alfa that you can buy in smaller quantities.

I just wanted to try the manufacturer's recommended gear oil; just for my own curiosity. I didn't realize it was so difficult to buy individual quart containers...

[winders]

What are you guys talking about? You don't *NEED* LSD additive if you have an LSD. The LSD addictive actually causes the LSD to perform less well. The additive causes the LSD to slip more so you don't notice the LSD as much on the street. What's the point of having the LSD if you are going to put oil in that makes it reform less well??

You could run Swepco 201 in the Alpha and you can run Shell Spiral HD in the Porsche.....

[ROW911SC]

Originally Posted by winders

What are you guys talking about? You don't *NEED* LSD additive if you have an LSD. The LSD addictive actually causes the LSD to perform less well. The additive causes the LSD to slip more so you don't notice the LSD as much on the street. What's the point of having the LSD if you are going to put oil in that makes it reform less well??

You could run Swepco 201 in the Alpha and you can run Shell Spiral HD in the Porsche.....

OK, so then the Spirax would work for both, open diff or LS notwithstanding...

[Bill Verburg]

Originally Posted by LenS

OK, so then the Spirax would work for both, open diff or LS notwithstanding...

Shell Spirax is probably a very good oil, it's just that there is a decades long history of outstanding performance in street and track use of Swepco transaxle lube in 915 transmission

I di a very brief experiment way back when and tries M1 sythetic gear oil in omne of my 915s, it was a huge mistake and was drained and replaced w/ Swepco after only a week or so.

The Swepco on the right is what you want to use


Delvac is another Mobil product that is not the same as the M1 synthetic found at your FLAPS, this is a great product for G50 and newer trans. but is inappropriate for a 915, It is better for a track trans w/ steel syncros than for street though, for street use w/ std. brass syncros the regular gear lubes in your owners manual are going to provide better cold weather performance and adequate protection for normal street use.

Neither of the above lubes has any special extra LS additives and can and should be used w/ either open or lsd transaxles,

As Scott says the LS additive just reduces the effectiveness of the lsd, I guess some people want that, I wouldn't.

[KTL]

The limited slip additive reduces "chatter" in many limited slip units and that's one of the primary reasons for its use. But this chatter isn't really an issue with the Porsche LSDs. Regardless, I agree that if you want your limited slip differential to function most effectively, you don't want to use a gear oil with the limited slip additive.

One could also argue, who cares because the limited slip probably isn't performing it's function much at all anymore due to wear.

[DRACO A5OG]

Originally Posted by KTL

The limited slip additive reduces "chatter" in many limited slip units and that's one of the primary reasons for its use. But this chatter isn't really an issue with the Porsche LSDs. Regardless, I agree that if you want your limited slip differential to function most effectively, you don't want to use a gear oil with the limited slip additive.

One could also argue, who cares because the limited slip probably isn't performing it's function much at all anymore due to wear.

Hmm? Interesting, it will definitely save me money. Thanks Master KTL

[Matt Monson]

I'd use the Spirax. If the lsd chatters after its in there run to the gym dealer and grab a little bottle of ls additive.

[ROW911SC]

Thanks all. I was only trying to rationalize the purchase of a case of Spirax, if it made sense for my 911. Kill two birds with one stone... I've used Swepco in the past and will most likely continue to do so.

[Matt Monson]

Why wouldn't you put the Swepco in your other car?

[Corvus Corvax]

I have always used Kendall GL-5 dino-flavored trans oil, at the suggestion of Pete Zimmerman. I found that it shifted very much better when cold, and equally well when warm.

https://www.amazon.com/Kendall-1043927-NS-MP-Hypoid-Lubricant/dp/B004RNPLLO/ref=sr_1_1?ie=UTF8&qid=1478925328&sr=8-1&keywords=kendall+hypoid

[ROW911SC]

Originally Posted by Matt Monson

Why wouldn't you put the Swepco in your other car?

Because I just acquired the Alfa and the factory manual calls for the Spirax.

[winders]

Originally Posted by Matt Monson

Why wouldn't you put the Swepco in your other car?

Originally Posted by LenS

Because I just acquired the Alfa and the factory manual calls for the Spirax.

I'd put Swepco in the Alfa too if it were mine.

[Corvus Corvax]

Originally Posted by winders

I'd put Swepco in the Alfa too if it were mine.

I wouldn't. It shifts terrible when cold. And the Alfa transaxle is not connected to the engine housing, so it would take forever to get warm. I'm not even sure I'd use anything more viscous cold than Spirax.

[winders]

Originally Posted by Corvus Corvax

I wouldn't. It shifts terrible when cold. And the Alfa transaxle is not connected to the engine housing, so it would take forever to get warm. I'm not even sure I'd use anything more viscous cold than Spirax.

Wow. The 915 doesn't get warmed up because it is bolted to the engine....and the Alpha box doesn't stay cool because it isn't. But hey, you keep thinking what you want on that subject.

Shifts terrible when cold? I have never experienced that in a 915-equipped 911 using Swepco 201. Another fallacy you can keep believing if it allows you to sleep better at night.

[winders]

Originally Posted by DRACO A5OG

Hmm? Interesting, it will definitely save me money. Thanks Master KTL

You don't want to give me even a little bit of credit?

[Corvus Corvax]

Originally Posted by winders

Wow. The 915 doesn't get warmed up because it is bolted to the engine....and the Alpha box doesn't stay cool because it isn't. But hey, you keep thinking what you want on that subject.

Shifts terrible when cold? I have never experienced that in a 915-equipped 911 using Swepco 201. Another fallacy you can keep believing if it allows you to sleep better at night.

No, I only experienced it myself, and so have many other folks on this board, if you can actually read. But hey, tell yourself that conductive heat transfer doesn't happen. Physics argues otherwise, but hey, cool.

[KTL]

Originally Posted by winders

You don't want to give me even a little bit of credit?

Sorry to steal your thunder Scott! My only reason for chiming in on the slip issue was add some more commentary on what the additive is intended to accomplish- chatter reduction.

I wouldn't worry about using the Spirax HD 80W90. It's good gear oil and fits the GL-5 spec and the obsolete MIL-L 2105B spec