K11 Owners Group

Das Boot · Posted: Sun Dec 30, 2007 1:09 pm Post subject: Gear Oil

I don't know how many people belong to the MOA and get their magazine, but there was an interesting article by Paul Glaves on page 28 of the Jan 08 magazine. Glaves suggests that 75w140 gear oil is actually only to be used in transmissions and not in final drives. In doing some research today, I have to admit, I think he is correct. The gear oil recommended by BMW is the GL5 80/90 or 75/90!!! Not the 75/140 that many of us have been using!!! The original containers of BMW's 75/140 oil use to have the gears of a 5 speed transmission and now have a picture of a cockpit view of an R1100S which is kind of wierd now too. Anyway the descriptions of the GL5 80/90 states for use in transmissions, rear axles and final drives. The 75/140 description, which is made by the same company "Spectro" does NOT suggest use in the final drives.

I have used Mobil1 75/140 and the BMW/Spectro 75/140 in both my transmission and final drive for nearly 10 years now without incident. But it makes me wonder if I have been doing the right thing.

Another side note in his article covers hydraulic clutch fluid. I know for a fact one of my local dealers but in the newer Mineral Oil, in for a friend of mine's 2002 K1200RS. The stock used brake fluid, the dealer thought the mineral oil was a later retrofit, it's NOT!!! The communication with dealers and BMW leaves a lot to be desired.
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Dom

Das Boot · Posted: Sun Dec 30, 2007 1:19 pm Post subject:

I forgot to mention, by freinds owners manual for his 2002 K1200RS suggests GL5 gear oil in the final drive. If I remember correctly, BMW started selling their 75/140 gear oil around 1998.
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Dom

acftfliehr · Big Brick Rider Joined: 05 Nov 2007 Posts: 62

Yikes!!!

Got to change out the oil now if not sooner!!!

Thanks for the research and enlightenment.

lostboy · Joined: 19 Dec 2007 Posts: 5 Location: MD

I seriously doubt any rear drive failures have been caused by using 75W140 instead of 80W90. This is just another case of trying to find a scapegoat instead of the real problem. 75W140 manufactured by both of BMW's oil suplliers has been used for years without any trouble. Large numbers of RDU failures only began with the advent of K1100LT and then other models in the same vintage.

It is my opinion that these failures have two possible causes: either the RDU was assembled with too much preload (very likely given BMW's present quality control) or defective bearings.

Das Boot · Posted: Fri Jan 04, 2008 5:16 pm Post subject: Re: Transmission Oil

max · Posted: Tue Jan 08, 2008 11:37 pm Post subject:

Been running the 80/140 GL5 Valvoline in the gearbox & rear drive this last month, over some large (for me) touring distances... and the rear drive was definitely hotter to the touch (as in "oops, is that safe to keep the hand on?") compared to the old 80/90 GL5 I had in before... I'm wondering if the extra viscosity is counterproductive in the rear drive, eg throwing the oil out like a centrifuge and the viscosity is keeping it there, rather than entering back into the gear faces? (Also remembering that the K series drives spin the crownwheel up-and-over before they reengage with the pinion).

I've got more 80/90 and will be using that again in the final drive (with a good dob of moly CV joint grease for extra EP (extreme pressure) protection; the gearbox is better, but it has a deeper pool of oil, and contra-rotating shafts to ensure oil is always present...

Final thought: the old K100 drives did run cooler, probably because they had the whole swingarm as a heatsink, and the whole inner pipe of the driveshaft to conduct heat out of the pinion. Maybe heat expansion in the paralever setups (at the level of finesse the pinions require for setting up, it's possible) contributes to the wear scenarios?

Max