Transmisson Oil Question

[buck_y_lee]

Hi there.

The Clymer manual for my 95 RM smoker says to use 10w-40, SE or SF oil in the transmission.

Down at the local auto shop, all oils labelled as 'gear oil' or similar seem to have viscosities of 75w or thereabouts. There is one 'gear oil' I found which was 75w, but on the back of the bottle declares that it has a viscosity of a 10w-30 oil.

The only oil with a 10w-40 viscosity was a semi-synthetic 'engine oil', rated SL.

So I am quite confused and have several questions.

1. Am I supposed to use the 10w-40 engine oil in my tranny? Or do I go with the 75w gear oil?

2. If I do go with the 75w gear oil, why is the manual telling me to use a 10w-40 oil? Is there a difference between a gear oil and a transmission oil other than the viscosity?

3. Is it ok to use a 'better' rated oil, say an SL in place of an SE?

Thanks (a lot) in advance,
Buck.

 

[KX02]

Allot of people just use regular motor oil. Gear oil has a different method for determining it's viscosity, hence the higher numbers. I use Castrol MTX gear oil myself, but most people I know use motor oil because it's cheap. Either will work.

 

[buck_y_lee]

The Castrol MTX was the 75w oil which also said on the back that it had a 10w-30 viscosity.

Thanks for the reply, KX02. Most helpful.

 

[CaptainObvious]

I know this sounds confusing, but motor oil and gear oil use two different scales for reporting their viscosity. So a 10w40 motor oil and a 75w or 80w gear oil are about the same.

Any motor oil without friction modifiers (diesel oils come to mind), motorcycle specific oils, or even transmission fluid (Type F) will all work fine in your gear box.

 

[RM_guy]

I buy the cheapest 10w40 motor oil and change it every 2-3 rides. Just make sure it doesn't have "EC" (Energy Conservation) rating on the label. I've never had a problem.

 

[buck_y_lee]

Excellent.
Thanks for the help guys.

 

[JTurn36178]

Here is my 2c. from a guy that has worked for two major oil manuf. co.s in for the last 16 yrs.

Remember folks: He is talking about a two stroke only. The fella that said that gear and motor oils use a different rating is absoulutely correct, and this is just two of "many" different ratings used on sometimes the same products.

The idea of buying the "cheapest" 10w40 isn't always a good idea when considering gearbox oil. The polymers used in multi-vis oils sometimes don't create the best protection for meshing gears. The wet clutch factor is another reason I wouldn't use a multi-vis oil, without getting into a lot of techno whatever jargon. If I was going to use a motor oil, I would go with a straight viscosity motor oil. (EX. 30 w) 30 weight will cause clutch drag (only noticed by expierenced riders ) until it warms up. (This is what I personally use in the summer time.)Specialty oils such a gear oil etc. might be a better choice but cost more.

Just some food for thought.
Good Luck
JIM

 

[buck_y_lee]

Thanks JTurn.

I'm not concerned with price. A litre of gear oil isn't really any more expensive than a 10w-40 engine oil.
I am just confused as to why the manual tells me to use a 10w-40 oil. Why would it not just say to use a 75w gear oil?

 

[buck_y_lee]

For anyone interested, I tried both the 10w-40 engine oil and a 75w gear oil.

10w-40 felt a bit slippy. 75w feels good.

Thanks for the help.

 

[weav6385]

I just had this problem with a cr125 I just bought. I drained the oil and put 75w90 gear oil in it and the clutch would not fully dissengage causing it to jerk when I put into gear. I couldnt even push it around in gear with the clutch in. I took the clutch apart and cleaned everything with brake cleaner and replaced the oil with 10w30 fully synthetic royal purple. The bike runs great now! No more sticking. I will never use gear oil again.