Gear Box oil.

I have been told that some gearbox oils are GL5 these oils have an additive (EP) that attacks Bronze bushes. The oil I am useing Penrite 80-90 is GL4 these oils contain 50% less (EP).
I am concidering changing the oil now that I have been made aware of this information.
Am I the last to know? I hope that this information is valuble to other people who read this forum.

Dave R1 said:

I have been told that some gearbox oils are GL5 these oils have an additive (EP) that attacks Bronze bushes. The oil I am useing Penrite 80-90 is GL4 these oils contain 50% less (EP).
I am concidering changing the oil now that I have been made aware of this information.
Am I the last to know? I hope that this information is valuble to other people who read this forum.

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I think you will find that excessive heat will be the contributing factor that will start the reaction to your bronze bushings using GL5 oils
The pre unit AMC box would not get to that specific temperature...but will check out the penrite product all the same. Cheers

DaveR1 ☝☝
Years ago.. as in 30+ I received a booklet from either the NOC or a parts supplier in England not sure now.. that had a list by year and part#s... bearing recomendation....and of faulty parts and general running issues & other stuff on the Commando...it was bloody handy i remember... except im buggered if I know where it is now ....im sure it didn't cover lubricant analysis
Cheers L.A.B....im still confused

KiwiShane said:

Cheers L.A.B....im still confused

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Yes, it is an oil thread after all.

As far as I'm aware, the majority of GL4 oils are safe to use and some GL5 (Redline?) at least I've never encountered the "gold in the gearbox" problem with any GL4 (or Redline) gear oil I've used although some are advertised as being "yellow metal safe".
Whether that's a marketing gimmick I couldn't say.

A regular 85W 90 140 non-synthetic is plenty good. I use the Lucas brand.

I had an '07 BMW R1200GS that specified a 5-GL g/b lubricant... the catalytic converter was about an inch directly under the g/b. Also, which makes little sense to me, Ariens specifies a 5-GL for the auger drive g/b on their snow blowers...

Best

RoadScholar said:

I had an '07 BMW R1200GS that specified a 5-GL g/b lubricant...

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As does my '85/'86 BMW K100RT's gearbox and bevel box although AN seems to think GL5 is something new on the market according to their recent gearbox oil video on youtube and with no explanation as to why GL5 is unsuitable for the Norton gearbox.

Many of the manufacturers of the GL5 oil state clearly where the oil can be used and in some cases where to actually avoid using it. EP90 was sold for years as GL4 but now it is being sold in both GL4 & GL5 spec. The GL4 spec is pretty common and easy to come by in other grades other than EP90 which itself is harder to find these days by the number of enquires we get each week. As time progresses I suspect we will all end up using GL5 oil as the older spec oil becomes harder to obtain, and we will find out if it causes the bushes to degrade quicker or not as the case maybe though most gearboxes would be rebuilt prior to any wear becoming evident. In the meantime it makes sense to avoid the oils that are not recommended by the their own manufacturers for use in our gearboxes unless you have no other option, that coupled with the fact GL4 has done us good for years just makes sense to use the GL4 spec oils at the moment.

I have no experience with GL 5 in motorcycle gear boxes, but have found they don't work as well in synchronized automotive transmissions with brass or fiber synchronizers. GL 5 has friction modifiers and is too slippery to allow the syncro to slow down the gear for easy engagement. GL 5 is best for limited slip differentials to allow the friction or locking disk to slip a bit when turning corners. Have not seen GL5 damage brass in automotive transmissions, it just doesn't work good in that application.

Madnorton said:

EP90 was sold for years as GL4 but now it is being sold in both GL4 & GL5 spec.

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GL5 always has been an 'EP' oil as far as I'm aware, just that the EP designation is not as widely used.

In the video, it is stated that: "...there is also a GL5 variant now appearing on the market that is not suitable..." and no further explanation of the "variant".

Madnorton said:

The GL4 spec is pretty common and easy to come by in other grades other than EP90 which itself is harder to find these days by the number of enquires we get each week.

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Looking online it's awash with vendors selling EP90 GL4 so I cannot see how it is in any way "hard to find".

Madnorton said:

As time progresses I suspect we will all end up using GL5 oil as the older spec oil becomes harder to obtain,

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Unlikely, in our riding future I'd think because it's still possible to buy GL1.

Madnorton said:

In the meantime it makes sense to avoid the oils that are not recommended by the their own manufacturers for use in our gearboxes unless you have no other option, that coupled with the fact GL4 has done us good for years just makes sense to use the GL4 spec oils at the moment.

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Maybe so but it doesn't mean all GL5 gear oils are unsuitable or detrimental even now as the information in the video would lead us to believe.

L.A.B. said:

Maybe so but it doesn't mean all GL5 gear oils are unsuitable or detrimental even now as the information in the video would lead us to believe.

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The main difference between GL-4 and GL-5 gear oils is the amount of EP additives. Sulphur/Phosphorus containing products are used as EP-additive. This additive has the purpose to prevent the occurrence of micro-welds on the gear flanks at the local high temperatures which prevail in EP circumstances (temperatures well in excess of 800℃!) GL-5 has roughly twice the amount of EP additives compared to GL-4, which is why it is often used in high-pressure circumstances such as in a front axle and rear axle differential.

Sulphur/Phosphorus additives however have an unfavourable property: they can react aggressively towards bronze and copper. This can be disastrous for the synchromesh rings [or bushes] of a gearbox. Therefore it is not recommended to use GL-5 in a gearbox unless the manufacturer allows this.

To conclude:

• GL-4 is suitable for hypoid gear service when they are under severe service but are without shock loading.

• GL-5 is suitable for hypoid gear service under severe service and shock loads and not for use in a gearbox."

https://www.rymax-lubricants.com/blog/the-differences-between-gl-4-and-gl-5/

"There are two types of sulfur compounds used — active and inactive sulfur. The main difference is that for active additives, the sulfur-containing additive reacts with the surface at much lower temperatures, whereas inactive compounds react only at much higher temperatures."