What is it with this GL-5 gear oil??

[Joe Papa Sr]

The shop manual says 87 spider gerbox requires GL-5, then you do the research, and learn the gL5 is mainly gl4 with additives, mostly made for HYPOID gears, which have nothing to do with the gearbox gears, as the hypoid gears are in the differential, right (cautiously asking, hoping for agreement).

So what is the big deal with gl5, if, when you look at what, say, IAP offers, they advertise that "later than 69 alfas need GL5", then go on to explain that Spirax 80-90HD GL5 does not have the aditives that can ruin synchromeshes.

How can you make sense of it all? If you say the spec is GL5, then turn around and say Spirax is GL5 but without additives, when GL5 is basically WITH these additives , made for the hypoid gears, which are not even in the gearbox!! That is contradictory.

It is a mess. I am considering using GL4, as it is , in my research, recommended for MOST manual transmissions, and for extending synchro life.

Whocares about an oil for the differential in this mater.........

[Alfacliff]

i drained hypoid oil out of my transmision and put in redline mtl. it is not quite as heavy as the 80-90 recomended, but really smoothed out my transmission. the previous owner put in some kind of hypoid oil and it crashed in every gear. now there is only a little crunch in second during cold weather.
I have some shell spirax I am going to try, since that is what Alfa recomends.
cliff

[lowmileage]

Quote:

Originally Posted by Joe Papa Sr The shop manual says 87 spider gerbox requires GL-5, then you do the research, and learn the gL5 is mainly gl4 with additives, mostly made for HYPOID gears, which have nothing to do with the gearbox gears, as the hypoid gears are in the differential, right (cautiously asking, hoping for agreement). So what is the big deal with gl5, if, when you look at what, say, IAP offers, they advertise that "later than 69 alfas need GL5", then go on to explain that Spirax 80-90HD GL5 does not have the aditives that can ruin synchromeshes. How can you make sense of it all? If you say the spec is GL5, then turn around and say Spirax is GL5 but without additives, when GL5 is basically WITH these additives , made for the hypoid gears, which are not even in the gearbox!! That is contradictory. It is a mess. I am considering using GL4, as it is , in my research, recommended for MOST manual transmissions, and for extending synchro life.

[lowmileage]

Quote:

Originally Posted by Alfacliff i drained hypoid oil out of my transmision and put in redline mtl. it is not quite as heavy as the 80-90 recomended, but really smoothed out my transmission. the previous owner put in some kind of hypoid oil and it crashed in every gear. now there is only a little crunch in second during cold weather. I have some shell spirax I am going to try, since that is what Alfa recomends. cliff

[Alfacliff]

no, it is 75w something, only a little thinner than the 80w90. possibly you are thinking ot the lube similar to automatic transmission lube popular with newer cars.
cliff

[oldschooleuros]

I am now confused. Some additives such as friction modifiers can be required to work in some geared devices, but I am not really sure if that is the reason behind this....

[lowmileage]

Quote:

Originally Posted by Alfacliff no, it is 75w something, only a little thinner than the 80w90. possibly you are thinking ot the lube similar to automatic transmission lube popular with newer cars. cliff

[Zunige]

The confusion stems from the preference to use Redline synthetic oils. For the differential Redline 75W/90 is great. It contains EP (Extreme Pressure) modifiers. The EP modifiers however, make the oil too slippery to use in the gearbox, as the synchros won't like this. Thus, for the transmission one must use synthetic Redline 75W/90 NS. The "NS" (Non-Slip) being the critical designation, meaning that it does not contain the EP modifiers that make the oil too slippery.

I would encourage a search, as there are a number of posts on this subject.

Best regards,

[lowmileage]

Unfortunately, this doesn't answer the question of using Spirax GL5 in the gearbox.

[Joe Papa Sr]

Quote:

Originally Posted by Zunige The confusion stems from the preference to use Redline synthetic oils. For the differential Redline 75W/90 is great. It contains EP (Extreme Pressure) modifiers. The EP modifiers however, make the oil too slippery to use in the gearbox, as the synchros won't like this. Thus, for the transmission one must use synthetic Redline 75W/90 NS. The "NS" (Non-Slip) being the critical designation, meaning that it does not contain the EP modifiers that make the oil too slippery. I would encourage a search, as there are a number of posts on this subject. Best regards,

[Joe Papa Sr]

Quote:

Originally Posted by lowmileage Unfortunately, this doesn't answer the question of using Spirax GL5 in the gearbox.

[Alfacliff]

redline mtl is "Manual transmission lube" it works for me. a lot better than whatever the prevoius owner put in.
cliff

[lowmileage]

Quote:

Originally Posted by Joe Papa Sr Right. So why do they claim their GL5 does not have the modifiers, if GL5 is supposed to contain them(scratching scalp like a primate, confused).......

[Anfanuts]

Quote:

Originally Posted by Zunige The confusion stems from the preference to use Redline synthetic oils. For the differential Redline 75W/90 is great. It contains EP (Extreme Pressure) modifiers. The EP modifiers however, make the oil too slippery to use in the gearbox, as the synchros won't like this. Thus, for the transmission one must use synthetic Redline 75W/90 NS. The "NS" (Non-Slip) being the critical designation, meaning that it does not contain the EP modifiers that make the oil too slippery. I would encourage a search, as there are a number of posts on this subject. Best regards,

[Elio Comello]

I believe the GL1/GL4 designation is for the NON Moly synchro's in the earlier gearboxes.

Alfa Factory spec PA38150000