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Final Drive Gear Lube Analysis


Steve Kolenda

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Steve Kolenda

Recently sent a sample of final drive fluid from my 2000 R1100RT to Blackstone Labs. Received the report back today and the only thing that they noted unusual was the viscosity of oil appeared to be in the low 20W/50 range. My dealer changed the fluid the last time so I don't know if they used 75W/90 or 75W/140. Any suggestions as to why the viscosity would be low? Also with the analysis what other types of materials should I be looking for if I am concerned about the final drive failing? When I originally contacted them they told me "We actually have pretty good averages for this type of system, so if a problem is developing, we should be able to see it." I will give them a call tomorrow to see if they having anything to add to their report specifically regarding a failure.

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Steve it sounds like they thought it was engiene oil.. Probably not too bad as gear oil & engine oil don't use the same viscosity scale.. A 75W-90 gear lube viscosity equates close to about a 15W-45 engine oil viscosity..

 

Twisty

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Could be, although their report states gear lube. I will ask them tomorrow.

 

Steve, well if they did rate it on the gear oil scale it is down a bit.. Maybe still not too unusual as anytime you run oil through a gear set under load it shears to a lower viscosity.. The more polymers in the oil & the longer it is run the lower the viscosity gets.. If it wasn’t a premium or synthetic gear oil to begin with & was run a fair amount of miles it can shear down pretty good.. Blackstone is a very good company so see what they say about it..

 

Twisty

 

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Steve Kolenda

I called the folks at Blackstone today to inquire about the viscosity issue and thinking about the previous oil change which was done at the dealers (first time since final drive failure in 05,normally change myself) noted that the oil could have been 75W90 instead of the 75W140 that I had stated. They plugged 75W90 into their program and the results matched exactly. They also stated that the rest of the analysis looked very good. I will probably send off another sample in 12,000 miles or so.

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gear oil & engine oil don't use the same viscosity scale.. A 75W-90 gear lube viscosity equates close to about a 15W-45 engine oil viscosity..

 

Twisty

 

Who would have thunk that? Not me.

 

You, sir, are a veritable font of useful mechanical information.

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Yes, of course the nomenclature is the same but the scales are different... after all, it's more confusing that way...

 

 

viscosity_table.jpg

 

 

 

 

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viscosity_table.jpg

 

 

 

 

Confusing, but it makes for prettier pictures... The artist here, I think, imposes a feeling of balance and symmetry upon an angry backdrop. A compelling contrast of fear and fairness.

 

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