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Transmission oil question


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I am getting ready to change my transmission oil and the manual says Grade SAE 90 GL5.


Yet I have read posts and people referring to 75w90 or 75w140. So what is the difference?





R1200RT 2005

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The difference between a single grade like an SAE90 and the multi grade oils that have a winter rating is not that apparent for you SoCal guys. If you live where there IS a winter- you want your oil to move and lube in the cold.


The use of the 75w-140 may be heavier than the designr intended. You should stick with the oil that has a GL5 rating and max viscosity of 90.


Which oil is of course another question and since we haven't had a good oil thread for a while, I will toss out that I prefer Amsoil Severe Gear 75W-90 and do so based on this test:



I can tell you I put it in my R12RT and I believe it shifts better as a result.


Do what you want but stick with the 90.


In case you are wondering about the multi viscosity thing... there is a lot of confusion about it. The best description I have heard goes like this... At low temperatures the oil will act as if is viscosity is the lower number... in this case 75, but at higher temperatures it will thin out (note: all oils thin out at higher temperatures) no more than a single viscosity oil of that viscosity- in this case 90.


So, there you go.

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I agree with your oil recommendations.


"I can tell you I put it in my R12RT and I believe it shits better as a result." But it might need Imodium? :grin:


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Just want to verify, access to the transmission is behind the right fairing above the rear brake, correct?



2005 RT

Yes,,,,lower over the center stand,I cut up a milk jug to use to keep it from running all over the stand,,,,
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One other thing- unless it is too late... best to figure out how you are going to get the oil into that vertical hole before you have to clean it off the side of the motor and center stand not to mention the spreading pool of 75W-90 on the garage floor.

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drzep, thanks for the reminder, done!


hopz, I used a long funnel, it work very well.


Thanks to all, this forum is a great resource and I found a lot of very useful post using the search function.


I just completed my 24k service plus new tires front rear and ended up saving about $500 vs the dealer. I enjoy working on my own vehicles and I learned quite a bit from this effort (my first "service"). Just got back from a quick ride and all is well...bike even seems to shift and run smoother.


Thanks again!



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Actually the lower number in a multi-viscosity oil identifies the base oil used. The upper number represents how the base oil behaves at elevated temperatures due to the additive package used. So a 5W-50 is a 5-weight oil that has viscosity modifiers added so it exhibits the characteristics of a 50-weight oil at elevated temperatures.


Cool huh???


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+1 on the Amsoil 75W-90. Have it in transmission and rear end and use Amsoil 20W-50 Motorcycle Oil in the engine. Bike runs and shifts like a dream.

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