Gearbox oil

[bsarider]

Hi All, Could you tell me what oil to use in the gearbox of a 1949 A7 Plunger,In my Comet I use a mixture of Grease and EP 90 and it doesnt leak at all. The book says
1 pint of 20/50 GTX or similar for the A7 any tips on what other people use to keep the oil in? thanks

[LJ.]

First of all I think we need to understand what EP90 or what ever number used is.

I have been using EP140 a really thick gear box oil and suffered no leaks, in fact gear changing was quite pleasurable and a delight to perform... But!

I have often heard of damaging effects of the use of EP, so I decided to look up just what EP is. The oil I had been using was Morris oil and the five litre container made no mention of any warnings of its use in older gearboxes. The website http://www.morrislubricants.co.uk/lubricants/company.asp?wp=91 FAQ mentions in greater detail what EP is and its reccomendations.

Of that page link above see...

4. What does EP mean?
EP means extreme pressure and refers to the additive used in gear oils. This additive is designed to stop metal-to-metal contact taking place between transmission components. The EP additives are usually based on sulphure and phosphorous. These elements bond to the metal surfaces where there are points of extreme pressure and temperature, forming a sacrificial chemical layer. The sulphur gives gear oils their characteristic smell.

8. Why should I choose non-EP straight oils for my classic car?
Depending on the age, make and model, non-EP gear oils may be required for use in gearboxes and final drives. Certain designs contained a lot of phosphor bronze (copper containing) components that are sensitive to the sulphur-based extreme pressure (EP) additive. The sulphur attacks the copper and destroys the integrity of the meshing gear surfaces.

Needless to say after reading this I flushed my gearbox through with some cheap 20/50 and rode a couple of hundred miles. Draining that I now use a straight Castrol 50 grade oil with no leaks and so far seems okay.

[fido]

That's interesting. I'm not sure if it was on here or another classic bike site but someone was claiming that only the early versions of EP oils were prone to attack bronze components and current products were perfectly safe in old gearboxes 

[Brian]

I've been using EP80/90 gear oil in all my bike gearboxes for as long as I can remember, including my Guzzi that has done 85,000k's, and I have never had a problem.

[BSA_54A10]

The early EP oils did attack all copper based bushes.
If you are as old as me you will remember gear & diff oils being marked as either "Safe for bronze bushes" on "not to be used with bronze bushes"

Now all this changed with the introduction of syncromesh gearboxes.
Syncro cones are typically brass so oils were marked as "syncro safe"
Gearbox and Diff oils went there seperate ways around this time.
Next came automatic gearboxes which killed off the seperate gearbox oil so most oil companies went to the more expensive EP addatives and went to combined gear & diff oils again.
So the rule of thumb is if it just says diff then forget it.
Do not use "truck" gearbox oils as trucks usually are all balls & rollers.

[fido]

Surely automatic gearboxes use ATF, a purpose made product which is more than just a lubricant.

[BSA_54A10]

Yes Fido.
Auto gearboxes use ATF
So there were less manual gearboxes .
So there was less manual gearbox oil sold
So it was uneconomic to make 2 different types of gear box oil
So the older ( cheaper ) type was dropped 

[alanp]

Whoops. I have a habit of adding Molyslip G to my classic gearboxes which is molybdenum diSULPHIDE. I wonder if the sulphides have been munching on the bronze bushes? I'll contact the makers.

[a10 gf]

bsarider:

any tips on what other people use to keep the oil in

Maybe find the source of the leak and fix it...

[fido]

They do tend to leak even when in perfect condition. There are no seals on the gear lever shaft, the kickstart shaft or the speedo drive.

[a10 gf]

Fido, I agree, but it shold not be some really bothering amount. But if worn too much things become more difficult, AFAIK it's possible to fit bronze bushes. As for the interim solution, the oil\lubrication can't be too thick either, I would not fill it with wheelbearing grease  it's got to circulate in there,  and be easy to change regularly.

[LJ.]

There are no seals on the gear lever shaft

This explains perfectly why my right boot never has a shine like my left one!  

[a101960]

Whoops. I have a habit of adding Molyslip G to my classic gearboxes which is molybdenum diSULPHIDE. I wonder if the sulphides have been munching on the bronze bushes? I'll contact the makers.

Oh dear so do I 

[BSA_54A10]

Molly is safe for use with bronze bushes . It should say so on the label