GL-5 Gear oil

[derbyjoe]

I tried to search the threads on this subject and I did not find much info. Can it be used in place of GL-4 gear oil in the middle and rear drives?
Thanks,
joe

[TopCatGr58]

Hey Derby,

I just did a GOOGLE search for GL4 vs GL5 and found lots of info.

Here are a few quotes on the differences between the two oil types:

•API Category GL-4 designates the type of service characteristic of spiral-bevel and hypoid gears in automotive axles operated under moderate speeds and loads. These oils may be used in selected manual transmission and transaxle applications.
•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.

GL-4; Specified for hypoid gear service under severe service but without shock loading. This classification is essentially obsolete but is still specified by some manual transmission/transaxle manufacturers. Implies an EP/AW additive package that contains 30% to 50% less S-P(Sulphur/Phosporous) additives than the GL-5 service classification. Some Marine Gear Lubes fall into this classification, especially the full Synthetic Marine Gear lubes and specialty blenders MT lubes that use high levels of esters.

GL-5; Specified for hypoid gear service but with shock loads and severe service operation. Usually meets Mil-L-2105D and in most cases, is the multipurpose automotive gear oil. Most 75W90 to 75W140 grades meet the GL-5 classification. This grade has a high level of Extreme-Pressure additives that could be mildly corrosive to nonferrous parts, such as brass, bronze and aluminum parts. Most of the modern GL-5 lubes contain metal deactivators that prevents attacks by the extreme-pressure additives. In addition to EP additives, these lubes contain rust inhibitors, defoamants, friction modifiers, thickeners, and Viscosity Index Improvers.

From what I've found, the GL-5 additives and or increased viscosity either releases acids under heat exposure breakdown that attacks the softer metals of the bearings...or the viscosity is too thick which doesn't provide as free flowing oil surface protection for said softer bearing materials.

SO.....with our older machines, with aluminum housings and unobtainium parts, I would check all of the oil supplier outlets you can to get the GL-4 stuff...like NAPA vs. Walmart/Autozone, etc....IMHO .

BUT..others with more formal mechanical and engineering training and experience may chime in with an alternate opinion....or even some facts!

T.C.

[WMarshy]

Interesting info... I just picked up some 85W140 GL-5 synthetic blend from Valvoline and planned on putting it in my middle drive. After reading your info about it possibly attacking aluminum I might not use it, although I have been right along. Im not sure if you can even get GL-4 gear oil, I don't ever recall seeing it on the shelf. Might have to take a trip to Tractor Supply and see if they have any... I looked at the price of full synthetic and I didn't dare to even pick up the bottle... any of you guys know if your full synthetic is GL-5 or something else?

The Dura-blend synthetic blend 85W140 I just bought was about $7 and change for a quart. I bought it because it said it has superior qualities over the non synthetic... maybe I'm just gullible... I think I will call the help line on the bottle and ask them if there is a material compatibility issue with aluminum.

[TopCatGr58]

What's that old proverb....?

It's better to be silent and be thought a fool than to speak and prove it?

This morning I went out in the garage and decided to check the bottles of 80/90 wt hypoid gear oil I had purchased and installed in both my machine as well as a few others that I had helped work on.

Right there on the label...the COASTAL(generic Walmart) brand stated it was rated API GL-5, GL-4, GL-3. The Castrol brand was also rated GL-5, GL-4. I had installed the Castrol back in 2000 with my rebuild, and although I've not taken my middle and final drives apart to inspect the condition of the bearings and such......they seem to be working just fine.

And since these and probably other gear oils are listed with multi-API ratings, that they are probably safe for our applications and use. Perhaps if a gear oil were ONLY rated GL-5, then it might have the above mentioned higher ratio of sulfur/phosphorous additives which could cause problems...but again it's stated that this increased acidity develops under the higher stress/shock of heavier types of transmission and gear sets..which ours don't undergo!?

Also, the Owner's Manual states using the 80/90 wts, and above an oil rated to 140 was mentioned, which might be too viscous??

Again, still looking for others input!
T.C.

[natemoen]

It's better to be silent and be thought a fool than to speak and prove it?

This morning I went out in the garage and decided to check the bottles of 80/90 wt hypoid gear oil I had purchased and installed in both my machine as well as a few others that I had helped work on.

Right there on the label...the COASTAL(generic Walmart) brand stated it was rated API GL-5, GL-4, GL-3. The Castrol brand was also rated GL-5, GL-4. I had installed the Castrol back in 2000 with my rebuild, and although I've not taken my middle and final drives apart to inspect the condition of the bearings and such......they seem to be working just fine.

And since these and probably other gear oils are listed with multi-API ratings, that they are probably safe for our applications and use. Perhaps if a gear oil were ONLY rated GL-5, then it might have the above mentioned higher ratio of sulfur/phosphorous additives which could cause problems...but again it's stated that this increased acidity develops under the higher stress/shock of heavier types of transmission and gear sets..which ours don't undergo!?

Also, the Owner's Manual states using the 80/90 wts, and above an oil rated to 140 was mentioned, which might be too viscous??

Again, still looking for others input!
T.C.

I have a mix of GL-4 and GL-5. I have a little 1 gal jug of GL-4 and then I have some quart bottles of GL-5. I think I got the 1 gal of GL-4 at wal mart a couple years ago. Dont know which I put in though....

[BA80]

•API Category GL-4 designates the type of service characteristic of spiral-bevel and hypoid gears in automotive axles operated under moderate speeds and loads. These oils may be used in selected manual transmission and transaxle applications.
•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.

GL-4; Specified for hypoid gear service under severe service but without shock loading. This classification is essentially obsolete but is still specified by some manual transmission/transaxle manufacturers. Implies an EP/AW additive package that contains 30% to 50% less S-P(Sulphur/Phosporous) additives than the GL-5 service classification. Some Marine Gear Lubes fall into this classification, especially the full Synthetic Marine Gear lubes and specialty blenders MT lubes that use high levels of esters.

GL-5; Specified for hypoid gear service but with shock loads and severe service operation. Usually meets Mil-L-2105D and in most cases, is the multipurpose automotive gear oil. Most 75W90 to 75W140 grades meet the GL-5 classification. This grade has a high level of Extreme-Pressure additives that could be mildly corrosive to nonferrous parts, such as brass, bronze and aluminum parts. Most of the modern GL-5 lubes contain metal deactivators that prevents attacks by the extreme-pressure additives. In addition to EP additives, these lubes contain rust inhibitors, defoamants, friction modifiers, thickeners, and Viscosity Index Improvers.

I think y'all are over analizing. What the manual calls for is what was best when these bikes were new 30 years ago. There have been some significant improvements on that in the last 30 years.

I run Royal Purple 75w140 full synthetic in my middle and final drives. Its GL4 & GL5 rated. They run a lot quieter. Betcha the aluminum will still be fine 30 years from now.

[motoman]

Nothing wrong with any of those choices. A few years ago, dropped the oil out that was in both my drives and replaced it with synthetic RoyalPurple 75w140w. No more whine from drives at speed. Also, did a test run at that time slabbing it on the Interstate @75-80mph from G.Junction to GreenRiver, Utah some 125miles. At the truck stop there, fueled up for return and layed my hand on side of final drive and wasn't hot enough to remove my hand. That pretty much convinced me. Less heat equals less friction, equals less wear, plus no more of that notorious whine from middle and final drives......JAT for others here.

[clcorbin]

At the truck stop there, fueled up for return and layed my hand on side of final drive and wasn't hot enough to remove my hand. That pretty much convinced me.

VERY nice info! I've always been a bit concerned how hot the middle drive gets after prolonged running. Mine definitely gets hot enough that I can not keep my hand on the cover for very long. Time to get some Royal Purple and see if it cools it down.

[WMarshy]

Middle drive oil is recommended to be changed every 5000 miles according to the manual. I change mine every year and typically ride about 7000.... I could see a clear difference in breakdown from the middle drive from the rear. Think about running the rear oil a little longer this time around... put synthetic blend 85W140 in the middle just the other day...

[BA80]

Middle drive oil is recommended to be changed every 5000 miles according to the manual. I change mine every year and typically ride about 7000.... I could see a clear difference in breakdown from the middle drive from the rear. Think about running the rear oil a little longer this time around... put synthetic blend 85W140 in the middle just the other day...

Really? I found just the opposite. Middle drive oil was clean but the FD oil was dark. I put about 15,000 on mine last year before the change this spring.

The synthetic should be able to go at least twice as far as the dino.

[Douglas Money]

From what I understand, the GL-4 does not attack the bronze parts, while the EP additives in GL-5 can. Some manufacturers are saying to only use GL-4 in certain applications due to this. The aluminum will be fine. I know of some people that are using GL-5 in a GL-4 only application and haven't had any problems.....yet.

[XSive Okie]

GL-5 is the latest and greatest API rating. Shouldn't be a problem using it in place of GL-4 (which could be hard to find in some markets). The API runs tests year after year, and makes a decision FOR US on what is best. That's why automtive engine oil has dwindeled down from "straight 30 weight" to full synthetic 0W20. If you ever grab a bottle of it and shake it, it has a viscosity somewhere between water and transmission oil!

[motoman]

Thirty year old reccomendations don't mean squat on these scoots Marshy.......including thirty year old tire pressure reccomendations! After making that change to Royal Purple on both, checked with the plastic dipstick, and both still show see-thru purple oil. That was after 20K.....and haven't looked at it for a couple years now.......no leaky internal or external, so not worried about it in the least. If anyone questions that decision, got a story pertaining to that with my ole' original motor's middle drive.....so trust me.....not winging it here!.....PM me if interested.

[derbyjoe]

Thanks for all the input. I found 80-90 GL-3, GL-4, GL-5 rated gear oil at NAPA. I figured that it may be better than straight GL-5 rated oil in that it may not have all the additives.
joe

[Lbrown311]

GL-5; Specified for hypoid gear service but with shock loads and severe service operation. Usually meets Mil-L-2105D and in most cases, is the multipurpose automotive gear oil. Most 75W90 to 75W140 grades meet the GL-5 classification. This grade has a high level of Extreme-Pressure additives that could be mildly corrosive to nonferrous parts, such as brass, bronze and aluminum parts. Most of the modern GL-5 lubes contain metal deactivators that prevents attacks by the extreme-pressure additives. In addition to EP additives, these lubes contain rust inhibitors, defoamants, friction modifiers, thickeners, and Viscosity Index Improvers.

From what I gathered, it's not that it is released during high levels of extreme pressure, but that it contains these additives "at all times". The key word here is "MILDLY" corrosive, which could take several decades to deteriorate some metals. Another note to take a look at is this line:

Most of the modern GL-5 lubes contain metal deactivators that prevents attacks by the extreme-pressure additives.

So if you want to use the GL-5 and are scared of the repercussions of it, find one that uses the metal deactivators. Should say on the label what is all in it. I personally will be using the GL-5 rated oil, simply for the reduced heat index from using it. That alone should be enough for anyone to consider using it. High heat = High friction = Faster deterioration. Higher viscosity levels, one would think, "should" create a better environment for gears, to an extent. But it would take a pretty viscous oil to prevent those gears from doing their job. JMO!