GL-5 no no
- Thread starter Old Henry
- Start date
Old Henry
Well-known member
If you don't mind GL-5 it's fine. It is GL-5 lubricant. It's like what I use in my stock differential.
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JSeery
Member Emeritus
Almost all gear lubricants say something similar to that and are backwards compatible with GL-4 requirements. That is a different issue than "yellow" metal safe. You have to check the actual ratings. Some have even reported problems with GL-5 products that claim to be "yellow" metal safe, so why take the chance? A GL-5 rating is not required in a manual transmission so why use it?
"GL-5 is not necessarily backward-compatible in synchro-mesh transmissions which are designed for a GL-4 oil: GL-5 has a lower coefficient of friction due to the higher concentration of EP additives over GL-4, and thus synchros can not engage as effectively. Also, transmissions which explicitly call for GL-4 oil may have been designed around this lower concentration of EP additives and thus may contain yellow metal parts which GL-5 will corrode."
"Gearbox oils are classified by the American Petroleum Institute using GL ratings. The higher GL-rating the more pressure can be sustained without any metal-to-metal contact taking place between transmission components. Separate differential usually have higher pressure between metal parts than gearboxes and therefore need higher GL-rating. For example, most modern gearboxes require a GL-4 oil, and separate differentials (where fitted) require a GL-5 oil."
"API Category GL-5 designates the type of service characteristic of gears, particularly hypoids in automotive axles under high-speed and/or low-speed, high-torque conditions. Lubricants qualified under U.S. Military specification MIL-L-2105D (formerly MIL-L-2015C), MIL-PRF-2105E and SAE J2360 satisfy the requirements of the API GL-5 service designation."
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JSeery
Member Emeritus
That is the term gear lube suppliers use. It means a lubracation specified GL-5 meets or exceeds GL-4 specifications. This is confusing because just because it meets and exceeds lubracation requirements does not mean it is safe for "yellow" metals. At one time in the past GL-4 was specified for rear axles for example. When GL-5 became available it was listed as also acceptable to use in rear axles originally specifying GL-4 (backward compatible). BUT, this applies ONLY to it's lubracation qualities, NOT to compatibility with 'yellow' metal (synros, bushings, etc.)
50fordcoupeman
Well-known member
I was looking at a local auto parts house for GL-4. The parts person said that GL-5 was ok to use in my synchro ******. I showed him on one of his GL-5 bottles it said and I quote " Not for use in synchromesh transmissions". He said oh I didn't know that. Pretty clear to me....................
V8COOPMAN
Well-known member
I'm sure he'd be "more qualified" if he got a raise to $15/hr. Unfortunately, our world is full of 'em! DD
flatford8
Well-known member
Ok..... got it.....Thank you......Mark
Ford Freak
Well-known member
JSeery
Member Emeritus
There are several reports of the supplier tech folks giving the same type of answers! I think it's the "yellow" metal confusion, because all of the GL-5 lubes say they are fine for GL-4 applications from a lubrication prospective. Another problem is it is not an instant problem type of deal, it takes time to show up. The EP additive bonds to the yellow metals and then peals off at a microscopic level. So over time it peels off the surface one layer at a time.
As stated above-- so over time it peels off the surface one layer at a time. So what is the definition of over time? 1 year 10 years 100 years? Has anyone had a failure of their synchro rings using GL-5 that says it's safe for yellow metals?
I have been using it for about 3 years so far with a transmission that has a little over 50,000 miles on it and it made shifting easier and the transmission quieter after the change.
JSeery
Member Emeritus
It depends on the pressure on the part and the number of cycles. If you like the GL-5 use it, the information is for the folks who care about these issues. No matter what the topic is someone has always been doing it for 50 years with no problem. Just seems to be the way it is. You would think the transmission manufactures telling you not to use it would be enough.
An added note: There are some newer GL-5 lubes that claim to be safe. It is not the GL-5 rating that is the issue, it is the EP additive. If some suppliers are using different additives that would make a difference.
An added note: There are some newer GL-5 lubes that claim to be safe. It is not the GL-5 rating that is the issue, it is the EP additive. If some suppliers are using different additives that would make a difference.
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1937pickup
Well-known member
Old Henry,
Have you asked Mac VanPelt what he recommends using in his rebuilt transmission? I think he would be the definitive source on this information.
Have you asked Mac VanPelt what he recommends using in his rebuilt transmission? I think he would be the definitive source on this information.
Old Henry
Well-known member
I didn't ask him, neither did he volunteer a recommendation. Neither did he say there was any excessive wear on any of my "yellow metal" since I replaced them two years and 33,000 miles ago. I've had my transmission opened up for rebuild/inspection 4 times in the last 10 years, 100,000 miles, and have never seen any excessive wear of "yellow metal". That's using GL-5 lubricant. So, although the theory of GL-5 causing excessive wear of "yellow metal" parts probably makes sense, in actual practice I doubt it's enough for anyone to actually notice, especially anyone just driving their cars a few miles a year. Even so, since I'm driving mine 10,000 miles a year, I'm doing anything and everything anyone suggests to make my transmission last longer. May not make a difference but, then, again, maybe it will. It's worth the effort "just in case."
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1937pickup
Well-known member
Old Henry, I was re-reading your previous post regarding Mac's rebuild and how happy you are with the service. I came to a post by a Pete VS who said he purchased some ****** parts from Mac and had him send him some transmission oil. Mac sent him GL-4. After reading this I will be changing my transmission from GL-5 MT to GL-4.
jake197000
Senior Member
on any newer vehicles we work on we try to use what the manufacturer recommends but on older cars we use GL-5 in pretty much everthinghave never had a problem that i know of in 40 years.im sure there is valitity in the debate but i think its overblown.a race car or the like maybe but i dont think its a big deal on an old thre or four speed.this is a general statement.i dont worry about it much
Ron Pilger
Senior Member
This discussion has been valuable. While some posters view the information being conveyed as redundant "old news", i am thrilled to get new professional opinion and amateur perspective, alike.
I have worked in the advertising field for the past forty years. The original post and the discussion which has followed reminds me of timeless training in my career:
The first time people look at any given ad, they don't even see it.
The seventh time, they see the message they start to get a little irritated with it.
By the seventeenth time of seeing that lousy ad, they make a note to buy the product.
By the twentieth time a prospect sees the ad, they go buy the product that will solve their need.
With this in mind, thanks for reopening good discussion on this age-old topic. And for sharing your individual thoughts. It is clear that many people, even veterans in this stupid hobby, are in some cases just getting exposed to this perplexing oil dilemma. I'm especially pleased that the original post didn't get taken down as quickly as it went up.
I have worked in the advertising field for the past forty years. The original post and the discussion which has followed reminds me of timeless training in my career:
The first time people look at any given ad, they don't even see it.
The seventh time, they see the message they start to get a little irritated with it.
By the seventeenth time of seeing that lousy ad, they make a note to buy the product.
By the twentieth time a prospect sees the ad, they go buy the product that will solve their need.
With this in mind, thanks for reopening good discussion on this age-old topic. And for sharing your individual thoughts. It is clear that many people, even veterans in this stupid hobby, are in some cases just getting exposed to this perplexing oil dilemma. I'm especially pleased that the original post didn't get taken down as quickly as it went up.