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Transmission leak after service.

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johndeeredr

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Sep 7, 2024
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156
Location
madera ca
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Bike
R1800B
Replace my transmission oil on my R1800B . Went for a couple hundred mile ride and noticed some gear oil on my garage floor directly under the transmission. But I traced the steam of oil and it appears to be coming from the top rear or the engine . It’s not coming from the driveshaft seal but above it behind the engine cowling . Is there a vent there? Maybe I overfilled it ? Not sure but would appreciate some advice . I had some Bel-ray 85 - 140 hypoid gear oil left over from my Harley Days. And filled with 1.15 liters. Or 50 .72 oz .
 
Mine had a leak from a hole in the transmission breather. There was at least one other person here that had the same issue.
 
I have been reading a bunch of threads on this transmission breather issue .my thoughts are that if that much oil is making it up and saturating that breather . That’s the oil level is too full or it’s at the full mark and when oil gets hot , it’s expands . My thoughts are is to fill with 1 liter and no more. .150 milliliters should not make any difference other than giving the oil of choice more room to expand. Thoughts on this theory?
 
johndeeredr said:
I have been reading a bunch of threads on this transmission breather issue .my thoughts are that if that much oil is making it up and saturating that breather . That’s the oil level is too full or it’s at the full mark and when oil gets hot , it’s expands . My thoughts are is to fill with 1 liter and no more. .150 milliliters should not make any difference other than giving the oil of choice more room to expand. Thoughts on this theory?
Click to expand...
Mine was actually split. It’s been replaced and it’s all good.
 
johndeeredr said:
Were is it located and how do I access it ? Might be worth looking into
Click to expand...

johndeeredr said:
Were is it located and how do I access it ? Might be worth looking into it.
Click to expand...
From the service ticket after they replaced the breather.

  1. Removed L/R Battery covers, throttle body covers and airbox covers and confirmed leak coming from breather.
  2. Removed L/R throttle bodys, air filter, seperated air box from bracket and engine.
  3. Inspected breather valve, covered in oil, small hole present in exterior rubber. BMW approved replacement and running of bike w/o covers to confirm fix. Performed extended test ride to confirm leak no longer present.
 
I did it myself, 20 Bucks part ... Pain in the @ss to change I did post pictures, but I can't remember in what thread
 
If you overfill the transmission, the fluid will start to froth and expand; also, going outside of the recommended oil chemistry, weight or going cheap could also result with the same frothy outcome... ultimately leading towards leaking from the breather .. which I guess is doing its job, especially if overfilled.
 
Ok , drained out all the Bel ray 85-140 hypoid gear oil . Almost 2 liters. Way too much .cleaned all the gear oil with electronic cleaner . Added 1Full liter on 75 -90 GL -5 . . Drove around 50 miles at high speeds 80 to 90 mph . Rode it like I was being chased . ……. No leaks . Breather is clean . In my opinion. That little rubber breather was just doing its job . To vent the transmission case has the oil in expands and warms up . The dynamics of the gears and the flow of power to the output shaft and using the wrong gear oil was my problem. Stay what with BMW recommends But Do not fill it to specs . Remember. You will never drain all the oil out . If you rebuild the transmission , yes , fill to full specs . When replacing during normal service , only add 1 full liter only . Also make sure the bike is level. Front to back and side to side . If you can’t manage that . Measure what was drained and Only add that amount back .
 
Remember that transmission breather vents to the outside atmosphere. Overfill with oil OR. Using the wrong oil can cause a lot of problems.
 
johndeeredr said:
Ok , drained out all the Bel ray 85-140 hypoid gear oil . Almost 2 liters. Way too much .cleaned all the gear oil with electronic cleaner . Added 1Full liter on 75 -90 GL -5 . . Drove around 50 miles at high speeds 80 to 90 mph . Rode it like I was being chased . ……. No leaks . Breather is clean . In my opinion. That little rubber breather was just doing its job . To vent the transmission case has the oil in expands and warms up . The dynamics of the gears and the flow of power to the output shaft and using the wrong gear oil was my problem. Stay what with BMW recommends But Do not fill it to specs . Remember. You will never drain all the oil out . If you rebuild the transmission , yes , fill to full specs . When replacing during normal service , only add 1 full liter only . Also make sure the bike is level. Front to back and side to side . If you can’t manage that . Measure what was drained and Only add that amount back .
Click to expand...
I typically measure the oil that I drain, especially when getting into a new platform - in this case, a 2022 R18 Model B. When I changed the Transmission fluid, I captured 1.15 L ( or 1,150 mL ) of fluid; which, worked out to being exactly what the manufacture recommends adding into the Transmission case. Engine Oil, I'm OK using Mobil 1 and other brands like that ... however; when it comes to the Transmission and the Rear Bevel Gear Drive - I'm a little more comfortable using the BMW branded oil, which I typically buy in bulk when BMW dealerships run discount promotions during the Holidays. I'm not a chemical engineer, so I'm trusting that the BMW folks are recommending an oil that doesn't froth and breakdown within the transmission case; my previous 2008 R1200 GS Adventure had almost 100,000 miles on it and never had a major failure; only went into the service shop for warranty work, front shock service and replacement tires...

That said, I'm thinking you might be a little low Transmission fluid wise and using the incorrect weight (75-90) vs SAE 70W-80; which might cause issues down the road...? Below is a page from my personal maintenance book as a reference:

1730550446863.png
 
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