gl-4/gl-5???

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ok, i think i am starting to get a handle on this gear oil thing, gl-4 = anti wear additives, gl-5 extreme pressure additives, so what is gl-4/5 ( motul gear300 sae 75w90)
which then begs the question: what is gl-6, i thought it was an obsolete rating, but sure i've seen it on the shelves recently
confused.gif
 
GL6 is mostly advertising and is obsolete.

GL4 and GL5 denote the EP protection level of the gear lube. Both have EP additives and AW additives, just different treatment levels.
 
I went to Kragen and all the gear oils only referred to GL-5. None of them said GL-4 compatible.

My manual calls for GL-5 or higher in the differentials and GL-4 for the transfer case. I thought GL-5 might hurt the soft metal parts in a transmission. Is that not right? If GL-5 is OK for my transfer case why does my manual specifically call for GL-4?
 
Most differential lube manufacturers list the GL5 rating because the majority of differentials require that protection rating.

Let's clarify that Manual Transmission Fluids (MT's) and Differential lubes are two entirely different lubricants and their formulations reflect that fact.

GL4 is sometimes specified for components such as TC's and MT's because many mechanical engineers lack any knowledge about gear lube formulations. GL4 refers to the level of EP protection provided by the lubricant.

Some people think that GL4 offer a less aggressive "attitude" toward non-ferrous parts such as the copper alloys of brass and bronze commonly used in sychronizer assemblies.

And let me state this for the nth time, modern GL5 lubricant formulations are safe in most components/units. When there is a mismatch, it is usually a mismatch between viscosity and friction modification.

Winston, what vehicle?
 
I have an '03 Mitsu Montero.

quote:
Let's clarify that Manual Transmission Fluids (MT's) and Differential lubes are two entirely different lubricants and their formulations reflect that fact.

GL4 is sometimes specified for components such as TC's and MT's because many mechanical engineers lack any knowledge about gear lube formulations. GL4 refers to the level of EP protection provided by the lubricant.
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These two statements confused me for a while, but I think I get it now.

The problem is that when I go to Kragen, they have a bunch of "gear oils". Valvoline, Mobil 1, etc. They are all labled as "gear oils" and they all say Gl-5. They do not have some gear oils for MT's and TC's and other gear oils for differentials. So you are essentially saying that you would never use one of these dino gear oils in your transmission because they would not work very well. Right? They would not hurt any thing, they just would not work too well.

Then you go to some high end oil brands like Redline and they market specific gear oils for Manual transmissions and other gear oils for differentials. (All good stuff no doubt).

So, you are saying that you should use gear oil specifically formulated for MT's and another type of oil specifically formulated for Diffy's. It is just that the GL4 GL5 has nothing to do with it.

As you can see from the links, I have question this before. I guess I am just a slow learner regarding this issue. I think Ive got it no.

I think I have just made the water more muddy.

[ March 09, 2006, 04:43 PM: Message edited by: Winston ]
 
Winston,

I just changed the rear differential gear oil in my 02 sonoma.It calls for a GM part number that is gl4 rated. However, nothing on the marked is labled as gl4. I picked up some valvoline durablend 80w90 labled as gl5. Now, on the product sheet on valvolines website it claims to have an api service of gl5 as well as gl4.
http://www.valvoline.com/products/Durablend Gear Oil.pdf

This should work, or you could check with the manufacturer to see if the stuff you want to use is also gl4 rated.
 
^
that is if I understand what MolaKule has been saying about GL4/5 and I didnt muff up my rear diffy.

****it Jim I'm a biologist not a mechanic.
 
quote:
They do not have some gear oils for MT's and TC's and other gear oils for differentials. So you are essentially saying that you would never use one of these dino gear oils in your transmission because they would not work very well. Right? They would not hurt any thing, they just would not work too well.
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Right! However, if the shifting was really crappy, you could damage the sychronizer assembly or the shifter fork assembly.

quote:


Then you go to some high end oil brands like Redline and they market specific gear oils for Manual transmissions and other gear oils for differentials. (All good stuff no doubt).

Click to expand...
Right again!

quote:


So, you are saying that you should use gear oil specifically formulated for MT's and another type of oil specifically formulated for Diffy's.

Click to expand...
Correct!
cool.gif


quote:


It is just that the GL4, GL5 has nothing to do with it.
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Here is a general guideline:

For a Manual Transmission speced for GL4 you can use a Manual Transmission fluid with either a GL4 or GL5 or GL4/5 dual rating.

For differentials speced for GL5, you must use a GL5/MT-1 rated fluid of the correct viscosity.
 
Mola, please explain how the "buffering" in dual rated GL4/5 oils performs in the long term. I know each transmission reacts differently to different oils, but what happens to a dual rated oils after say 100K miles?

The copper strip test is an indication of the corrosivity of a virgin gear oil, but there's no test to gauge when said buffers may be "spent" (again, since every transmission/differential acts differently). This is the reason I rather go GL4 only.
 
How about using gl 5 in the rear diffy when the specs call for gl 4? I know this probably has been answered a thousand time, but i aint too bright.

It seems to be working well so far, but its only been about a week.
 
ccs2, go with a high quality synthetic GL-5, and just change the oil more often.

It's been said here before (and I'm sure Mola would agree) that there are virually NO passenger car or small truck gear oils available (whether used in a transmission, transfer case or diffy) that should be pushed more than 50,000 miles -- regardless of what the manufacturer says, and regardless of formulation.

The only exception to this that I am aware of is with open-road trucks with very large differential sump sizes.

Do some reading in the used oil analysis section for gear oils, and you'll see for yourself.
 
quote:
Originally posted by ccs2k1:
Mola, please explain how the "buffering" in dual rated GL4/5 oils performs in the long term. I know each transmission reacts differently to different oils, but what happens to a dual rated oils after say 100K miles?

The copper strip test is an indication of the corrosivity of a virgin gear oil, but there's no test to gauge when said buffers may be "spent" (again, since every transmission/differential acts differently). This is the reason I rather go GL4 only.
Click to expand...
Good question ALL S/P type GL-4/5 gear oils at some time over use WILL cause brass corrosion they are inhibited for this BUT you must run a "normal" change out say 30K or so.

Chevron borate gear lube will run 100K as I rmember with no problems.
bruce
 
Thanks Bruce. I do wish gear oils had something like a TBN number to get an idea.

VistaMan, my transmission calls for a straight GL4, so the only choices would be dual rating and straight GL4, but I just don't feel confortable w/ GL4/5s.
 
quote:
Mola, please explain how the "buffering" in dual rated GL4/5 oils performs in the long term. I know each transmission reacts differently to different oils, but what happens to a dual rated oils after say 100K miles?
Click to expand...
We have tested to over 50k and the tbn retention was good, but our transmission fluids start out with a high tbn and a low TAN. Our fluids start out with tbn's of around 10 and above with TAN's of 0.2 to 0.5 or less.

We use EP additives with included metal deactivators and corrosion and rust inhibitors and add additional MD's and CO's for long term stability.

What you want to watch for is the Total Acid Number or TAN in a fluid analysis. When it gets over 3 you want to look for trends of increasing TAN or hopefully a stable TAN.

If the drain plug (or sometimes the fill plug) will have a magnet on it. Look at the magnetic plug and see if it has just has a fine paste on it, then the wear is probably low. Also look at the fluid in a small transparent PET bottle and look for any small yellow flakes, which would indicate some synchro assembly and sleeve bearing/bushing wear. Most well built transmissions will have needle and ball bearings.

Of course, a good UOA is the best way to analyze wear by looking at the iron, tin, copper, and aluminum elements, and of course compare the visocsity with the original (VOA) viscosity to detect any shearing. Someone like Terry Dyson can help with that task.
 
Mola,

If i exchange your MTL-P GL4/GL5 every third year this is approximately 30k for my running habits. My sychronizer assemblies cant be hurted in some way if following my maintenance plan above.

Car is Volvo XC70 2.5T AWD 5-speed manual stick MY 2003.

Right or wrong!

Another question is if i store MTL-P for five years do you think that the inhibitors protect the sychronizer assemblies is less good in shape compared to new fluid.

What would your advice be in this case. Can i run it for 3 years and 30k as well as new fluid.
 
3 Years or 30k sounds good to me unless you use Oil Analysis, then go with the results of oil analysis.

As long as the our fluids aren't exposed to a lot of moisture or mist (caps are tight), they have an expected life of 3 to 5 years after being openend.

The inhibitors are oil soluble and are not expected to degrade.
 
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