ZD18 mower 90W gear box oil compatibility

[eglaude]

Howdy y'all, it's been some time since I've been in to the forum and I have a question about gear oil specifications that is hard to find an answer for since it always "depends". I didn't even bother to call Kubota Support line since I most likely would have just wasted a lot of my time and becoming more and more confused.

My old trusted ZD18 has been a family member since 2001 and I have always used the best oils I could purchase as this little tank had to last me a lifetime when I first bought her. In fact that got me a few nights of sleeping with it in the shop when my wife found out what it cost us! She was wrong and knows it now as it has paid for itself so many times over that I will never not take care of it the right way.

The mower is the stamped RCK54-18Z version, it was all I could afford back then but would have loved the 60" fabricated one but there was just nothing left but selling my old truck for it. I have used the AMSoil Transmission/Transaxle gear lube oil GL-4 spec oil since at the time the manual called for "API spec "more than GL-3" which is tricky since there are many gear oils now that have a GL-4/GL-5 spec and I am aware of the "soft metal" corrosion issues that the additives in the GL-5 gear oils have caused historically. I have always been avoiding that like the plague.

I called AMSoil Tech Support on this as now 25 years later now they would be aware of more confident with the information about their gear oils for use in the Kubotas that would either support of debunk this myth. Well apparently they have a statement from Kubota that it is safe to use a API GL-5 gear oil in Kubota tractor gear boxes that call for a SAE90 gear oil.

Long way around to ask if it's still an issue to use a API GL-5 or should I just stick with the API GL-4 only? I have my L3400 front axle gear oil change out coming up in the fall and was going to standardize the gear oil with the ZD and get a case of the AMSoil 75W-90 GL-4, but it's quite a bit more expensive than their Severe gear oil that is 75W-90 with the GL-5 additive package. I can't say for sure if there are any "soft" metal bushings in either the tractor front axle or the ZD mower gear box, and to be honest I don't want to find out the hard way if it means "just try it". That is an awful lot of beer fund money down the drain!

Thanks y'all for your help, I appreciate it, and hope this can be a problem solved finally for the next 25 years as that ZD sill be right alongside me in that 6 ft hole when the time comes with a perfect gearbox! LOL!

 

[GeoHorn]

…

I called AMSoil Tech Support on this as now 25 years later now they would be aware of more confident with the information about their gear oils for use in the Kubotas that would either support of debunk this myth. Well apparently they have a statement from Kubota that it is safe to use a API GL-5 gear oil in Kubota tractor gear boxes that call for a SAE90 gear oil.
…

Since Amsoil sells GL-5 gear oils ONLY…. I would EXPECT them to safe it’s “safe” to use GL-5 oils in…Kubota… or any other oem that call for …gear oil.

Did they offer to forward the entire/complete Kubota statement to you? (Our family has two Ford tractors… a late 70s model and an old 9N… the Latter should not use GL5…it calls for GL-1…. But I’m pretty certain Amsoil would be happy to report that they have a “statement…that would say …it is safe to use a GL-5 gear oil in Fords that specify SAE90 gear oil….. because none of the Fords we own say that….and they likely do not actually have any document that transfers liability to anyone that uses a GL-5 oil in their equipt… In other words….what Amsoil has done is give you something for which you’ll Never be capable of holding Amsoil responsible.

(I don’t know what you mean exactly…by “soft” metals…. but I suspect you mean brass, bronze, or copper… and the “heavy duty” Extreme Pressure additives in GL-5 gear oil has a reputation of injuring those so-called “yellow” metals.)

Hope this helps.

(If you‘ve been reluctant to use GL-5 oils in equpt that specifies an earlier GL oil….and if that earlier oil is available on the common market…. I don’t know why anyone would take a Specialty-Marketer’s word for their product by them simply transferring responsibility on a third-party such a “statement” from an OEM ….which cannot be confirmed directly by that OEM.

But that’s just me.

 

[TheOldHokie]

Howdy y'all, it's been some time since I've been in to the forum and I have a question about gear oil specifications that is hard to find an answer for since it always "depends". I didn't even bother to call Kubota Support line since I most likely would have just wasted a lot of my time and becoming more and more confused.

My old trusted ZD18 has been a family member since 2001 and I have always used the best oils I could purchase as this little tank had to last me a lifetime when I first bought her. In fact that got me a few nights of sleeping with it in the shop when my wife found out what it cost us! She was wrong and knows it now as it has paid for itself so many times over that I will never not take care of it the right way.

The mower is the stamped RCK54-18Z version, it was all I could afford back then but would have loved the 60" fabricated one but there was just nothing left but selling my old truck for it. I have used the AMSoil Transmission/Transaxle gear lube oil GL-4 spec oil since at the time the manual called for "API spec "more than GL-3" which is tricky since there are many gear oils now that have a GL-4/GL-5 spec and I am aware of the "soft metal" corrosion issues that the additives in the GL-5 gear oils have caused historically. I have always been avoiding that like the plague.

I called AMSoil Tech Support on this as now 25 years later now they would be aware of more confident with the information about their gear oils for use in the Kubotas that would either support of debunk this myth. Well apparently they have a statement from Kubota that it is safe to use a API GL-5 gear oil in Kubota tractor gear boxes that call for a SAE90 gear oil.

Long way around to ask if it's still an issue to use a API GL-5 or should I just stick with the API GL-4 only? I have my L3400 front axle gear oil change out coming up in the fall and was going to standardize the gear oil with the ZD and get a case of the AMSoil 75W-90 GL-4, but it's quite a bit more expensive than their Severe gear oil that is 75W-90 with the GL-5 additive package. I can't say for sure if there are any "soft" metal bushings in either the tractor front axle or the ZD mower gear box, and to be honest I don't want to find out the hard way if it means "just try it". That is an awful lot of beer fund money down the drain!

Thanks y'all for your help, I appreciate it, and hope this can be a problem solved finally for the next 25 years as that ZD sill be right alongside me in that 6 ft hole when the time comes with a perfect gearbox! LOL!

The notion that a modern GL-5 formulation is overly corrosive is a myth. With a few exceptions (esp. Royal Purple) modern formulations use inactive/buffered sulfur compounds and are 100% yellow metal safe. The GL-4 specification is OFFICIALLY obsolete effective 8/2015 and has been for 20 years.

Nobody has been able to actually test an oil to the GL-4 specification for decades. Claims of GL-4 conformance are purely made up but API tolerated it based on a EP treat rate of 50% of the corresponding GL-5 formulation. Plus the GL-4 specification actually allowed more corroision in the yellow metal test.

This and reduced phosphorus (zinc) are the two biggest oil lies on the internet.

Dan

 

[TheOldHokie]

Since Amsoil sells GL-5 gear oils ONLY…. I would EXPECT them to safe it’s “safe” to use GL-5 oils in…Kubota… or any other oem that call for …gear oil.

Did they offer to forward the entire/complete Kubota statement to you? (Our family has two Ford tractors… a late 70s model and an old 9N… the Latter should not use GL5…it calls for GL-1…. But I’m pretty certain Amsoil would be happy to report that they have a “statement…that would say …it is safe to use a GL-5 gear oil in Fords that specify SAE90 gear oil….. because none of the Fords we own say that….and they likely do not actually have any document that transfers liability to anyone that uses a GL-5 oil in their equipt… In other words….what Amsoil has done is give you something for which you’ll Never be capable of holding Amsoil responsible.

(I don’t know what you mean exactly…by “soft” metals…. but I suspect you mean brass, bronze, or copper… and the “heavy duty” Extreme Pressure additives in GL-5 gear oil has a reputation of injuring those so-called “yellow” metals.)

Hope this helps.

(If you‘ve been reluctant to use GL-5 oils in equpt that specifies an earlier GL oil….and if that earlier oil is available on the common market…. I don’t know why anyone would take a Specialty-Marketer’s word for their product by them simply transferring responsibility on a third-party such a “statement” from an OEM ….which cannot be confirmed directly by that OEM.

But that’s just me.

This is another myth that has been roundly debunked. Ford NEVER specified GL-1 in any N-series tractor. The specification didn't even exist.

Beginning with the 9N FORD specified a "mild EP" gear oil in viscosity grades SAE 80 (M4864A below freezing) and SAE 90 (M4864B above freezing). The sole exception was the wartime 2N manual which specified "straight mineral oil" in those viscosities because EP gear oils were rationed and only available to the military.

Dan

 

[GeoHorn]

This is another myth that has been roundly debunked. Ford NEVER specified GL-1 in any N-series tractor. The specification didn't even exist.

Beginning with the 9N FORD specified a "mild EP" gear oil in viscosity grades SAE 80 (M4864A below freezing) and SAE 90 (M4864B above freezing). The sole exception was the wartime 2N manual which specified "straight mineral oil" in those viscosities because EP gear oils were rationed and only available to the military.

Dan

Well…your reply is correct…but a technicality….because the specifications which were later developed….assigned “GL-1” to mineral oil sans additives. Therefore, it is correct “current references” to discuss it as GL-1.

 

[TheOldHokie]

Well…your reply is correct…but a technicality….because the specifications which were later developed….assigned “GL-1” to mineral oil sans additives. Therefore, it is correct “current references” to discuss it as GL-1.

There is no "technicality" here. From day one Ford specified a "mild EP gear oil conformimg to M4864A or M4864B.". That is not "mineral oil sans additives" by any name.

Dan

 

[GeoHorn]

There is no "technicality" here. From day one Ford specified a "mild EP gear oil conformimg to M4864A or M4864B.". That is not "mineral oil sans additives" by any name.

Dan

Well…not to get into “tit for tat”….the Point was that the Term ”GL-1” became known later, in-reference to the oil recommended previously…. Therefore it is germane to use that term.

 

[hagrid]

"The goddamned germans ain't got nothin' to do with it!"

- Sheriff Buford T. Justice

 

[TheOldHokie]

I just had a look at the latest (9th) edition of API 1560. Very interesting

https://www.api.org/-/media/Files/Certification/Engine-Oil-Diesel/Publications/1560-Ninth-Edition-November-2023-Reaffirmed.pdf

3. Service Designations in Current Use

API GL-5

4. Service Designations not in Current Use

API GL-1
API GL-2
API GL-3
API GL-4
API GL-6
API MT-1

 

[eglaude]

Since Amsoil sells GL-5 gear oils ONLY…. I would EXPECT them to safe it’s “safe” to use GL-5 oils in…Kubota… or any other oem that call for …gear oil.

Did they offer to forward the entire/complete Kubota statement to you? (Our family has two Ford tractors… a late 70s model and an old 9N… the Latter should not use GL5…it calls for GL-1…. But I’m pretty certain Amsoil would be happy to report that they have a “statement…that would say …it is safe to use a GL-5 gear oil in Fords that specify SAE90 gear oil….. because none of the Fords we own say that….and they likely do not actually have any document that transfers liability to anyone that uses a GL-5 oil in their equipt… In other words….what Amsoil has done is give you something for which you’ll Never be capable of holding Amsoil responsible.

(I don’t know what you mean exactly…by “soft” metals…. but I suspect you mean brass, bronze, or copper… and the “heavy duty” Extreme Pressure additives in GL-5 gear oil has a reputation of injuring those so-called “yellow” metals.)

Hope this helps.

(If you‘ve been reluctant to use GL-5 oils in equpt that specifies an earlier GL oil….and if that earlier oil is available on the common market…. I don’t know why anyone would take a Specialty-Marketer’s word for their product by them simply transferring responsibility on a third-party such a “statement” from an OEM ….which cannot be confirmed directly by that OEM.

But that’s just me.

Howdy my freind @GeoHorn, and for starters thank you for the reply. I am not an expert in oil classification or hydrodynamics for various types machinery and applications, however I have worked my entire career, 35 years last year, in the the O&G exploration and product manufacturing and learned a thing or two about getting the right lubrication in a wide variety of extreme applications. It was always fascinating to work the huge aeroderivative turbo power generators that rely on such a thin film of oil to operate under the extreme speeds and temps that they were subjected to. Always a huge debate between "us" and the equipment manufacturer when it came to the lubricant brands during turnaround maintenance. I completely agree that there is a lot of talk by the manufacturers of these "boutique" oils but it always boils down to the owner to make the decision. In these cases, the equipment was in the tens of millions, and even with a whole bunch of paperwork and statements it was our company that paid the price one way or another.

I apply that same decision logic to most of my own equipment, e.g., tractors, mowers, chainsaws, and have done the research to make an informed decision when I totally change from the manufacturer's recommended product to something better that I know woks better. Classic example is 2-cycle oil, and unless the saw is under warranty, that "cheap" oil is the first thing that I change and the ratio as well.

Your comment on AMSOIL making GL-5 only is interesting, since I have used their products for tractor transaxles and gear lube for years now, and they definitely do have a "GL-4" classified product, i.e., MTGQT, and nowhere on the bottle does it mention GL-5 or lower. I really hate statements like that, "or better, or lower, since it's more of less legal jargon at that point. You are right, they[AMSOIL] did not come right out and offer the statement that Kubota endorses the use of GL-5 in their gear boxes and yes what I mean by the "soft" metals is perhaps more appropriate called "yellow" metals like brass bushings that are common in gear boxes. I have had experience in the effects of corrosive oils on these "yellow" or softer metals and it is a real problem if you get the oil wrong.

@TheOldHokie puts straight out on Gl-4 being obsolete for over 20 years now, and that is about as long as I have been using it now in my equipment. There is another brand of "speciality" oil that I use too, TRIAX, and they too have a GL-4 only gear lube AND a "severe gear" GL-5 for the off-road trucks. It still seems to be around, but I agree that the games played in marketing are made to make money and guess who pays no matter what!

I think that it's time for me "man-up" and switch to the GL-5 formulation since this is likely the same product that is in bottle that is for API GL-4 just with another additive. Hopefully it is "better" and perhaps I can put an end to my debates. Not only that but it's about 5 bucks a quart cheaper too!

Thank you for the discussion and if you do have any more experiences with this, or others that you know, please post them up here as this was a great discussion and perhaps shed the most light on this very ambiguous topic. Perhaps I can get the YT guy, "TheOilGeek", who I really admire, do a comparison test. Now that would go viral don't y'all think!

Take care,

Eric

 

[eglaude]

I just had a look at the latest (9th) edition of API 1560. Very interesting

https://www.api.org/-/media/Files/Certification/Engine-Oil-Diesel/Publications/1560-Ninth-Edition-November-2023-Reaffirmed.pdf

3. Service Designations in Current Use

API GL-5

4. Service Designations not in Current Use

API GL-1
API GL-2
API GL-3
API GL-4
API GL-6
API MT-1

Howdy @TheOldHokie , I just replied too, and I thank you for shooting straight to the point and I appreciate the link to the API publication. Knowing API too well, I sat on many API committees over my career, and they too have mastered the "legal language" on how to make a requirements and a suggestion one in the same thing.

It's high time for me to just change to the GL-5, and not only that but it's 5 buck cheaper than the GL-4 bottle!

Conserve for beer!

Thanks again for your help, I appreciate you digging in the weeds a bit and I feel a lot better now.

Eric

 

[TheOldHokie]

Howdy my freind @GeoHorn, and for starters thank you for the reply. I am not an expert in oil classification or hydrodynamics for various types machinery and applications, however I have worked my entire career, 35 years last year, in the the O&G exploration and product manufacturing and learned a thing or two about getting the right lubrication in a wide variety of extreme applications. It was always fascinating to work the huge aeroderivative turbo power generators that rely on such a thin film of oil to operate under the extreme speeds and temps that they were subjected to. Always a huge debate between "us" and the equipment manufacturer when it came to the lubricant brands during turnaround maintenance. I completely agree that there is a lot of talk by the manufacturers of these "boutique" oils but it always boils down to the owner to make the decision. In these cases, the equipment was in the tens of millions, and even with a whole bunch of paperwork and statements it was our company that paid the price one way or another.

I apply that same decision logic to most of my own equipment, e.g., tractors, mowers, chainsaws, and have done the research to make an informed decision when I totally change from the manufacturer's recommended product to something better that I know woks better. Classic example is 2-cycle oil, and unless the saw is under warranty, that "cheap" oil is the first thing that I change and the ratio as well.

Your comment on AMSOIL making GL-5 only is interesting, since I have used their products for tractor transaxles and gear lube for years now, and they definitely do have a "GL-4" classified product, i.e., MTGQT, and nowhere on the bottle does it mention GL-5 or lower. I really hate statements like that, "or better, or lower, since it's more of less legal jargon at that point. You are right, they[AMSOIL] did not come right out and offer the statement that Kubota endorses the use of GL-5 in their gear boxes and yes what I mean by the "soft" metals is perhaps more appropriate called "yellow" metals like brass bushings that are common in gear boxes. I have had experience in the effects of corrosive oils on these "yellow" or softer metals and it is a real problem if you get the oil wrong.

@TheOldHokie puts straight out on Gl-4 being obsolete for over 20 years now, and that is about as long as I have been using it now in my equipment. There is another brand of "speciality" oil that I use too, TRIAX, and they too have a GL-4 only gear lube AND a "severe gear" GL-5 for the off-road trucks. It still seems to be around, but I agree that the games played in marketing are made to make money and guess who pays no matter what!

I think that it's time for me "man-up" and switch to the GL-5 formulation since this is likely the same product that is in bottle that is for API GL-4 just with another additive. Hopefully it is "better" and perhaps I can put an end to my debates. Not only that but it's about 5 bucks a quart cheaper too!

Thank you for the discussion and if you do have any more experiences with this, or others that you know, please post them up here as this was a great discussion and perhaps shed the most light on this very ambiguous topic. Perhaps I can get the YT guy, "TheOilGeek", who I really admire, do a comparison test. Now that would go viral don't y'all think!

Take care,

Eric

This topic has been beat to death. Keep in mind these classifications are all performance based. They don't specify a chenistry. Overvtime the requirenents change to keep pace with chemistry and vice versa. For current performance requirements read these

Standard Specification for Performance of Rear Axle Gear Lubricants Intended for API Category GL-5 Service

store.astm.org

Standard Specification for Performance of Manual Transmission Gear Lubricants

store.astm.org

For some insight into gear oil chemistry you might want to read this.

https://www.infineuminsight.com/media/2965/09-gear-lubricants-na.pdf

And lastly, your mower gear box oil might be better classifued as an industrial gear oil (IGO) rather than an automotive gear oil (AGO)

Dan

 

[GeoHorn]

The typical rotary cutter (and similar) gearbox is straight-tooth gears…not the “hypoid” gears commonly found in automotive differentials.

The difference is the “sliding” surface characteristics of the gear-mesh.

I’m not an engineer with gearbox-design specific knowledge … but it doesn’t take much imagination to recognize there are likely different requirements to deal with friction, wear, and heat …depending upon the gear design.

”Second-guessing” which oil is “better” …according to the imaginative mindset of the owner…. may not… probably Does Not…. suit the gearbox better than what the designers/mfr’s of the gearbox specify.

If the mfr specifies GL4…then GL5 is Not Likely “better”…. just because the mind of the owner thinks the number 5 supersedes the number 4 ….

Use what the mfr’r specifies…is what I feel is best.

[Spoiler: My Rhino shredder ”specifies” a particular Esso lube oil…which I cannot locate anywhere. So it has ordinary NAPA GL5 80W90 in it. So much for my advice.)