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Discussion Starter #1
I know there were many posts about which oil to use for LSD rear axles. And I read all of them...
But it's still not clear to me, why most folks think that our LSD needs different oil than the non LSD or gearbox oil.
I am asking because the owner manuals of both my 87 Quadrifoglio and my 73 Berlina 2000 state that the gearbox, steering box and LSD all use the same SAE 80W/90 API GL5 oil.
So why not use what the factory recommends? Perhaps it's only an "urban legend"?
Also, do "friction modifiers" increase or decrease friction?
From ouner's manual - oils.JPG
 

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Lubricants are mainly intended to make surfaces slippery. Gearbox synchronizers and limited slip clutch plates (such as in our ZF limited slips) need friction to work. Friction modifiers are added to some gear lubricants to do just that.

If you pour in your rear end some GL5 gear oil that doesn't contain the proper mixture, the limited slip clutches will eventually enter a "stick-slip" mode that will cause an audible chatter. If this happens, the proper friction modifier is available under GM part number 88900330 or Redline 80301, to be added to your oil fill.

Gearbox oil is a science/religion in itself. GL5 contains a lot of anti wear and extreme pressure agents, a lot more than the mid-60s GL4 standard when moly synchros were introduced in our Alfas. Most current GL5 oils will be detrimental to synchro action. To make a long story short, many, many people have had good success with Redline 75W90NS in Alfa gearboxes. I'm sure there are other stuffs that will work fine, but we're on our own to find them. Some people use it as well in the rear end, but Redline's webpage specifically recommends regular 75W90 for LSD.
 

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Richard Jemison
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The right oil for the clutch type LSDs id the 75-90 NS. But if you are driving a street car with GL5 already you have reduced LSD function, and it apparently hasn`t been noticed.
 

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There is so much misinformation posted in web forums on lubricants, by "experts" who really don't know, I hesitate to say anything. I have had a business for the last 25 years dedicated to race prep, reman, service, and repair of transmissions for European sports cars - my credentials for what they are worth.

There is absolutely nothing wrong with using GL5 lubricants in transmissions. The notion that they degrade synchronizers is an Internet myth that gets copied and pasted. (The manufacturer of the marque I work mostly with issued a tech bulletin years ago insisting on use of GL5 in all transmissions, which for them means a wide range of balk ring, Borg Warner, and the newer three-piece cone designs. And yet, people keep quacking about the evils of GL5, and that their 40-year-old owner's manual calls for GL4.)

In terms of selecting a manufacturer and grade, bear in mind, NMS, that the page you've included in your post was written in 1986. A lot has happened since then, perhaps most notably the availability of synthetic lubricants. I have had excellent results with Mobil 1 75W90 for many years, in recent years rebranded as Mobil 1 LS 75W90. Mobil's Delvac is also a quality lube.

The friction modifies Yves mentions reduce or eliminate the chatter, but they do so at the cost of interfering with the proper operation of the LSD clutch discs. They chatter because they're supposed to lock and unlock. On a street car, street driven, it won't make a difference because you'll never really get the LSD doing anything noticeable for you. So use the friction modifier if the chatter bothers you. For track or autocross, no modifiers, let the LSD do its job.
 

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My experience is very specific to Alfa’s race cars. Redline 75/90 NS helps the synchros work better due to the lack of friction modifiers. On a street car, the LSD probably doesn’t care what you use. But in a race car, the “NS” definitely helps avoid slipping.
 

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Richard Jemison
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Catellus I certainly hope no one follows your advice. You are incorrect.
Here in the south your comment would declared full of schitt!

If you bother to read the back of a RedLine 75-90NS bottle it is specific to Alfa Romeo. Porsche, Ferrari transmissions and LSDs. And improves the action of the parts where privious use of common GL5 lubes have reduced the efficiency of the friction sensitive components..
 

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Discussion Starter #7
Thank you all for your inputs.
I guess there have been developments in oil technology since the 1986 owners manual.
But if there are so many contradicting opinions, the differences between various oils are probably not so great...
We don't have Red Line here in Israel, so I'll look for a LSD specific oil from a well known company (Castrol, Valvoline, etc.)
Happy New Year to all
 

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There is absolutely nothing wrong with using GL5 lubricants in transmissions
Several major oil manufacturers such as Shell and Valvoline have reintroduced gear oil to GL4 standard for manual gearboxes. I just wonder why that happened.

NMS, this product from Valvoline is formulated for LSD, but as Richard and Erik both pointed out, the way the ZF LSD is setup for our street Alfas is not very strong and just plain GL5 gear oil is not likely to cause a problem.
 

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Discussion Starter #9
Thanks for the pointer.
I found this Castrol oil (it's a British product), and it looks right to me.
It's a straight 90 weight, but we very rarely go below freezing here, so I'm not worried about that.
The car is only for street use.
1665849
 

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Thanks for the pointer.
I found this Castrol oil (it's a British product), and it looks right to me.
It's a straight 90 weight, but we very rarely go below freezing here, so I'm not worried about that.
The car is only for street use.
Ask yourself what problem you are solving by not using the recommended multigrade oil. You may not see freezing weather, but you will see your transmission's (and its fluid) temps swing from ambient to say 180 - 200F.
 

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To make a long story short, many, many people have had good success with Redline 75W90NS in Alfa gearboxes. I'm sure there are other stuffs that will work fine, but we're on our own to find them. Some people use it as well in the rear end, but Redline's webpage specifically recommends regular 75W90 for LSD.
I filled my transmission with Redline 75W90NS. It made a huge difference, my car seemed like it had a different gearbox. Almost cured my 2nd gear synchro issue for the most part, I seldom get any grinds. Also used Redline 75W90 regular in the differential, no issues.
 

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Alfar7 has rebuilt more Alfa transmissions than most people have seen. Take his advice.
 

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Discussion Starter #13
Ask yourself what problem you are solving by not using the recommended multigrade oil. You may not see freezing weather, but you will see your transmission's (and its fluid) temps swing from ambient to say 180 - 200F.
Good point, but It's for my LSD, not transmission (that's where the thread started :)).
I do think the transmission oil is a more sensitive choice.
 

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Discussion Starter #14
Alfar7 has rebuilt more Alfa transmissions than most people have seen. Take his advice.
I would love to- but they don't have Red Line here, and shipping a gallon is about $200...
So I'm looking for alternatives.
 

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There is so much misinformation posted in web forums on lubricants, by "experts" who really don't know, I hesitate to say anything. I have had a business for the last 25 years dedicated to race prep, reman, service, and repair of transmissions for European sports cars - my credentials for what they are worth.

There is absolutely nothing wrong with using GL5 lubricants in transmissions. The notion that they degrade synchronizers is an Internet myth that gets copied and pasted. (The manufacturer of the marque I work mostly with issued a tech bulletin years ago insisting on use of GL5 in all transmissions, which for them means a wide range of balk ring, Borg Warner, and the newer three-piece cone designs. And yet, people keep quacking about the evils of GL5, and that their 40-year-old owner's manual calls for GL4.)

In terms of selecting a manufacturer and grade, bear in mind, NMS, that the page you've included in your post was written in 1986. A lot has happened since then, perhaps most notably the availability of synthetic lubricants. I have had excellent results with Mobil 1 75W90 for many years, in recent years rebranded as Mobil 1 LS 75W90. Mobil's Delvac is also a quality lube.

The friction modifies Yves mentions reduce or eliminate the chatter, but they do so at the cost of interfering with the proper operation of the LSD clutch discs. They chatter because they're supposed to lock and unlock. On a street car, street driven, it won't make a difference because you'll never really get the LSD doing anything noticeable for you. So use the friction modifier if the chatter bothers you. For track or autocross, no modifiers, let the LSD do its job.
if you run a gl5 oil in a w/c t5 ( borg warner/tremec ) gearbox.( takes atf 4 or5 fuild ).. you rebuild the gearbox, with new parts.. and when i put gl5 in my oem alfa romeo tranny... it went to hell...shift liked,.doo doo had to carfully rinsh out the tranny with paint thinner, a few times.. rear end in the aid, tranny in 4 th gear, turning it over by hand... to get all that gl5 out, wash drain wash drain wash drain wash drain,, took all day to clean it out
 

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Discussion Starter #16
if you run a gl5 oil in a w/c t5 ( borg warner/tremec ) gearbox.( takes atf 4 or5 fuild ).. you rebuild the gearbox, with new parts.. and when i put gl5 in my oem alfa romeo tranny... it went to hell...shift liked,.doo doo had to carfully rinsh out the tranny with paint thinner, a few times.. rear end in the aid, tranny in 4 th gear, turning it over by hand... to get all that gl5 out, wash drain wash drain wash drain wash drain,, took all day to clean it out
Doesn't sound like fun :(
What oil did you put in after the rinse? Did it help?
 

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shell spirex oil.. i washed the box 4 times.. easy way to do it,, drain thru drain plug,, fill thru shift tower,, let sit for 20 mins, then drain.. repete a few times..fill tranny till it wont fill anymore thru shift tower, this way you know the paint thinner is at the top of the inside of the case.. some will leak out, thats ok.. then turn box over in 4 th gear, by rear wheels.. so it will get into every nook and cranny.. after that fill with shell.. work well after that.. thinner will not hurt any seals
 

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i am now running a w/c t5 on my car.. before with the oem engine, and now with my engine conversion...
 
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