GL5 and yellow metals: which spec is safe?

[kilou]

Hi,

there are a lot of discussion on this topic and I'm a bit lost. Sometimes it is said that if a GL5 is also rated as API-MT1, then it will be safe on yellow metals. My question: is the MT1 spec required for a GL5 oil to be safe for yellow metal?

I ask this because actually I use a GL5 lubricant (TransElf TRJ 75W80) which is only rated as being GL5 (as far as I know). However on the technical sheet, it is mentionned that it is appropriate to be used in manual transmission that uses brass synchronizer rings.

So is the MT1 spec required to be safe on yellow metals or not?

 

[MarkC]

I was sweating this about my Cherokee's manual 5 -speed. I finally got assurance that Amsoil wouldn't harm the brass, etc in there, so that's what I use.

If I have any problems, I will abuse Pablo!

(Not really)

 

[Pablo]

Modern GL-5 gear lubes will not harm brass.

 

[Michael SR]

i thought the MT-1 spec had to do with truck geaboxes which do not have synchronizers. i'm ignorant as to whether or not this means they still have yellow metals, though.

of course, that doesn't answer your question, but i don't think the issue is whether or not it's "safe" for yellow metals. there seems to be a difference in whether or not the synchro works well, apart from the yellow metal issue. most GL-4 lubes work great, but many GL-5 lubes do not. i haven't yet determined how to tell the difference, other than to try them, but (very) generally the full synth GL-5 lubes don't work well with synchros. (the subaru is an example of this, it requires a GL-5 but has synchros that don't work well with most GL-5 lubes.)

-michael

 

[Motorbike]

quote:

---

Originally posted by Michael SR:
i thought the MT-1 spec had to do with truck geaboxes which do not have synchronizers.

---

Correct .

Copper corrosion testing per ASTM D130 shows a value of 1B after 3 hours at 100 ºC. The scale goes from 1 (a,b or c) through 4 (a, b, or c). 1A means there is no effect of the lubricant on copper. 1B is the second best possible result. I am not aware of any true synthetic GL-5 gear lubricants being less corrosive to copper than 1B but there is always a chance . The copper corrosion test is used to measure the corrosiveness of lubricants to yellow metals .

When in doubt consult with the manufacturer .

 

[Kestas]

I think this is the test my STLE colleague uses to evaluate lubricants for use in our bearings that have brass cages. And yes, it's as simple as that -- if the lubricant doesn't attack pure copper as compared with the standards, it may be used in manual transmissions with brass synchronizers.

 

[TheLoneRanger]

I was told by a Coastal lube engineer that most if not all modern gear lubes were "buffered", so as to be safe on yellow metals. Coastal's lubes are rated GL3, GL4, and GL5 on the container. If your tech sheet says the lube is OK for manuals, I wouldn't worry.

The MT1 spec has to do with heavy duty truck and bus transmissions that are non-synronized.

To answer your original question, no, a gear lube dosen't have to be MT1 spec to be safe for syncros. The different specs deal with different criteria.

 

[Michael SR]

quote:

---

Originally posted by Motorbike:
Copper corrosion testing per ASTM D130 shows a value of 1B after 3 hours at 100 ºC. The scale goes from 1 (a,b or c) through 4 (a, b, or c). 1A means there is no effect of the lubricant on copper. 1B is the second best possible result. I am not aware of any true synthetic GL-5 gear lubricants being less corrosive to copper than 1B but there is always a chance

---

interesting. so you're saying the bad synchro action with some GL-5 lubes is indeed due to less than 1A results in that test?

i just looked up schaeffer's #267, and it claims 1A results to ASTM D-130. does that mean it would work well in my subaru tranny?

thanks.

-michael

 

[Audi Junkie]

If it smells like grease, don't use it. If it smells like Tide, it'll work in your ride,

 

[Motorbike]

quote:

---

Originally posted by Michael SR:

quote:

---

Originally posted by Motorbike:
Copper corrosion testing per ASTM D130 shows a value of 1B after 3 hours at 100 ºC. The scale goes from 1 (a,b or c) through 4 (a, b, or c). 1A means there is no effect of the lubricant on copper. 1B is the second best possible result. I am not aware of any true synthetic GL-5 gear lubricants being less corrosive to copper than 1B but there is always a chance

---

interesting. so you're saying the bad synchro action with some GL-5 lubes is indeed due to less than 1A results in that test?

i just looked up schaeffer's #267, and it claims 1A results to ASTM D-130. does that mean it would work well in my subaru tranny?

thanks.

-michael

---

Bad Synchro Action as you put it would be more a problem with the lube being too F/M'd IMO if the lube indeed was corrosive long term but had not been in long . These GL-5 XW-90 wt's come in various cSt's as well . From 10cSt to over 20cSt at temp . Some will work better when cold just by that alone then factor in how much slip is made into them .

The # 267 you ask ? I would not use it in any transmission personally . I might would an open differential in a hard working truck but not in the rear of a passenger car .

It's some thick stuff and I was once told it had a climbing agent in it .

 

[kilou]

quote:

---

Originally posted by Motorbike:

I am not aware of any true synthetic GL-5 gear lubricants being less corrosive to copper than 1B but there is always a chance . The copper corrosion test is used to measure the corrosiveness of lubricants to yellow metals .

When in doubt consult with the manufacturer .

---

Would you say that a GL5 oil performing 1B result to ASTM D130 test is a "safe" oil? Moreover is it possible that some GL4 have worst results at this test compared to some GL5 despite the fact they have almost 1/2 EP additive of GL5?

I'll try to contact Elf to know how performed my oil on this particular test but this information seems "impossible" to find......... I assume that these tests are performed by independent laboratories. If so would it be possible to contact these laboratories directly rather than contacting the manufacturer of the oil to get the info?

 

[Grossomotto]

Pablo said it right, "Modern GL-5 gear lubes will not harm brass"

I wouldn't use most 75W90 Synthetic GL-5 Differential Gear Lubes in a manual transmission. Although, you can and I doubt there will be any damage as a result. As you know, transmissions are very picky with the fluid used and many have proprietary blends like Toyota and GM.

Take Royal Purple Gear Max Synthetic (rated Gl-4 and Gl-5) for instance. You can use it in a variety of applications including front/rear diffs and manual trans. I've only used it in the diffs.

Other products from Redline, like their 75W90 Gear Oil, I would be careful with as well. Even their MT-90 (75W90) and MTL (70W80) manual trans fluids often have to be mixed 50/50 for good results.

This is from Redline (and may be outdated):

quote:

---

Most manufacturers of manual transmissions and transaxles recommend an 80W or 90W GL - 4 lubricant. GL - 5 gears oils which are required in hypoid differentials are not used in most synchromesh transmissions because the chemicals used to provide the extreme pressure protection can be corrosive to synchronizers, which are commonly made of brass or bronze. Typically, the use of a GL - 5 lubricant in a synchromesh transmission will shorten the synchronizer life by one half. The extreme pressure requirements of spur gears and helical gears found in transmissions are not nearly as great as found in rear-wheel drive differentials. A GL - 4 lubricant provides adequate protection for most manual transmissions, unless a unique design consideration requires the extra protection of a GL - 5.

---

 

[Pablo]

Grosso - I agree!! I was simply addressing the GL5/brass question based on Amsoil.

 

[Michael SR]

sorry to hijack the thread, but i've really been wondering about this a while...

is it possible, even, to make an MT90 but with a GL-5 rating? or are that type of synchro action and a GL-5 rating mutually exclusive? if not, why doesn't redline (or anyone else) make a synchro-sexy GL-5?

in the case of the subaru, (supposedly) the factory fill is VV820 (petroleum valvoline 75w90 GL-5). obviously that works well (but is extremely hard to find). but subaru doesn't make any distinction between a GL-5 that works well with synchros, and one that doesn't. how can the little man (me) figure out what to use?

(if the smell test is indeed a good method, it certainly doesn't help that i can't get my hands on all the GL-5 synths to smell them.)

thanks.

-michael

 

[wrangler]

Michael,

Redline does kinda make a "synchro-sexy GL-5". They 75W90 NS(non slip) gear lube. That should be good fit for a manual tranny that requires a GL5.

 

[mechtech]

It seems that most modern GL5s are buffered, but if it says GL4-GL5 on the bottle, it for sure is safe[r] with brass synchros.

 

[kilou]

The oil I'm using actually does not display any other specs except GL5

However this oil is recommended by the manufacturer of my gearbox (the gearbox is built by Renault but my car is a Volvo S40 european specs). Moreover it is written that this oil is to be used in manual trannys with brass synchronizer rings so I assume it should be safe. But........Elf does not provide any specs for that gearoil except that it's a GL5 and they do not reply to my mails so I won't know whether it is really safe or not (if it is they should advertise it, no?).