Final Drive Fluid

[Steve Kolenda]

Putting up my 2011 R1200RT for the season and changed the final drive fluid. Fluid looked very dark. The last two changes at intervals of 6,000 miles looked like they had just come out of the bottle. Not sure why the dark fluid all of a sudden. Bike has 57,276 miles on it.

[dirtrider]

Evening Steve

 

Did you use the exact same type/brand gear oil last change? If so then it might warrant a little investigation.

 

Maybe send a sample out to BlackStone labs for an analysis.

 

Possibly some grease leaking into the gear oil from the sealed crown bearing chamber.

 

OR, possibly just normal discoloration from moly in the gear oil.

[Steve Kolenda]

D.R.

 

Yes, exactly the same Castrol SAF XO SAE 75W90. The last change was after a 6,000 mile 2 week trip out West and the fluid looked like new. Will BlackStone be able to determine if grease is mixed in? Something has happened whether it is something to worry about or not is the question.

[dirtrider]

Morning Steve

 

You will probably have to call BlackStone & ask them. If they have your base gear oil on record they can tell a lot. If they don't then about all they can do is give you the amounts of what is in the gear oil.

[Steve Kolenda]

D.R.

 

I am going to send a sample to them and will post the results.

[VoipWizard]

If I may...:

 

I have read somewhere that moisture will cause the gold colored final drive fluid to become dark. Can that be the case?

 

 

 

 

[duckbubbles]

Usually, enough moisture in the oil (gear or motor) will cause it to become an opaque brown color- think sort of chocolate milkish. The rear gear oil in my '05 ST came out black for 2 or 3 changes and finally started coming out as it went in after that.

 

Frank

[racer7]

A really black mess originating from the Castrol FD lube that used to come out clean is a sign of a significant problem that you need to find. (Note that assembly grease often discolors the first couple changes on BMW bikes but once it comes out clean it should stay that way barring problems).

 

If it were me, I'd be starting with a thorough mechanical exam unless it was obvious that water in the lube was the cause (it is always obvious if you know what it looks like, otherwise analysis will tell you). Submerging a hot vented FD will get water in it and they do get pretty warm in normal operation.

 

The best way to examine the FD is remove the wheel, disconnect the driveshaft, remove the brake caliper drag and hand rotate it. If it rotates dead smooth no bearings or gears are damaged and the worst it can have (if anything) is a bad seal. The factory shake test is crude and not as sensitive, though less work.

 

Not getting the shaft boot on correctly can allow water to pool in the bearing area at the shaft- which can cause issues. Water trapped there is obvious on disassembly.

 

[Steve Kolenda]

Information from Blackstone report, any comments?

 

STEPHEN: Thanks for the notes. It's interesting that the oil was draining fairly clean in the past and it

suddenly turned dark here. Usually, dark oil just shows the oil is doing its job cleaning the unit and collecting

dirt, but maybe this is related to the high metals we found in this sample. Iron and chrome are both from

steel parts (chrome is an alloy) and should be lower than (or closer to) universal averages, which show

typical wear for a BMW final drive after ~7,400 miles of oil use. Suggest using 3,000 miles next time &

checking back. No contamination or excessive solids found.

 

Chromium 5 Unit/ Location Averages 2

Iron 361 Unit/ Location Averages 144

 

[Steve Kolenda]

Forgot to include the following information.

Universal averages for Chromium: 1

Universal averages for Iron: 89

[mneblett]

Feel any roughness in the crown wheel bearing when rotated by hand?

[Steve Kolenda]

Wheel movement appears to be smooth with no noticeable axial movement.

[Steve Kolenda]

No suggestions on what my next step should be?

[dirtrider]

Afternoon Steve

 

 

Sorry I missed this thread update for some reason

 

The high level of iron might or might not be a concern. The high iron usually comes from the ring to pinion teeth seating (wearing) in.

 

If from a vehicle that had history of gear tooth wear then I might be tempted to look inside at the tooth mesh, but the BMW 1200 has no history of any ring & pinion wear issues so you are probably only seeing normal tooth mesh wear-in.

 

I guess if it were my bike I would do as Blackstone suggests & do another gear oil change out around 3k just to see if the oil comes out cleaner.

 

 

 

[Steve Kolenda]

dirtrider,

 

Thanks for responding. We are planning a 6000 mile trip which would start at approximately the 3000 mile mark. I am concerned (maybe overly) due to the fact that the last two changes at approximately 6,000 miles each came out looking like the oil was right out of the bottle and this was very dark. Some have suggested water in the oil but the analysis came back with zero water.