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Transmission leak after service.

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Maybe, just maybe the oil is not the main issue here but the breather is. My previous bikes, a Yamaha Dragstar and a Suzuki M109R, were both shaft driven and I don’t recall seeing a breather plug in them.
 
update with my leak. replaced oil with 1 liter which is 936 milliliters of castro 75 -90 weight regular gear oil with limited slip additive. ran for 500 miles at rather high speeds and agressive shifting leak is totally gone. im convinced that i it overfilled and had the wrong oil in it. so i redrained it overnight. added back LIQUID MOLY 75 -90 FULL SYNTHTIC HYPOID GEAR OIL. ADDED BACK 1.100 LITERS. to be sure it was sligtly underfilled and ran another 500 aggressive miles. no issues with leaking from the breather. i purchased a new breather and if its not split or cracked, its just doing its job venting the transmission case to keep a zero pressure in it.
 
Star-Lord said:
Isn't the gear/transmission oil specification 70W-80...?
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Yes, that is what's stated to use, but 75 90 is absolutely fine to use. I have 30k miles on my r18b and change my fluids every 5k. I know it's overkill but I enjoy doing it. All I ever used was liquid moly oil and 75 90 gear oil. A lot cheaper than buying the bmw brand. Here's a link for the kit. https://www.beemerboneyard.com/r18etfdoilkit1550.html
 
I agree 100% with the more frequent preventative maintenance schedule; in fact, I woke up this morning, prepared to check and adjust the valves later this morning - early afternoon if out of tolerance...

Wife's Thanksgiving cleanup plans ruined a morning of pheasant hunting with the dog and a little wrenching therapy on the R18 B...

Will definitely get out on Thanksgiving morning for some upland bird hunting with the family dog, he'll be completely knocked out for when guest arrive...
 
Star-Lord said:
I'd be interested in hearing what they find or say; keep us posted.
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My dealer inspected and confirmed the vent was leaking...they replaced it with an updated vent. Don't know what the actual difference is but it looks very similar to the original.
I only rode it ~20mi home with no visible leak... I'll give an update after riding additional mileage which will be awhile with winter here...
 
The transmission leak is back from the vent area near top-rear of transmission housing after taking a ~80 mi ride yesterday...
 
After 34,000 miles on my 2022 R18TC, always dealer serviced I decided to change my transmission & final drive oil myself and found a moderate amount of metal on the magnets & in the BMW hypoid oil so... I filled both to the bottom of the fill hole, ran it about 200 easy miles then drained & re-filled with fresh 210ml Drive & 1150ml Trans. Used MOTUL 300 Gear 75w90 G4/G5. It took a couple hundred miles but the shifting is improved and it seems to have smoothed everything out a bit. Probably not necessary to flush like I did as the oil I put to the fill came out basically clean and nothing on either magnet but glad I did since I changed weights.... Yeah I know the BMW oil & MOTUL can mix but I preferred not to and am happy with the result.
 
JRD said:
Turns out the transmission seep from vent was due to using 75w90 oil... my dealer changed back to 70w80 BMW spec oil and no more seep...
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I'm using MOTUL Gear 300 G4/G5 75w90 (changed at 34,000) in my TC and after 500 miles no leaks, 34,500 miles now so maybe that's the difference? Thanks for the heads up tho, will keep an eye on it.
 
My brand new Roctane is in for its 1st service and developed what was at first a smell of trans oil at about 500 miles. I looked for the source but didn’t see anything leak. It became enough of a leak right before I took it in to leave spots on my new concrete though. Will call today to see if they found the source yet.
 
I agree it is probably the vent and mentioned it to them. I would be surprised if it was overfilled at the factory but who knows. I wouldn’t expect the cheap stuff to be used at the plant. 620 miles, 1st service.
 
The dealer replaced the vent on my new Roctane. They stated it was fixed. The ride home on the highway (about 35 miles) presented no leak being evident. Took it for a nice long 3 hour ride yesterday, about 155 miles total, and today the leak is back. Spot on the shop towels (learned my lesson last time) and oil present underneath at the back of the trans. Back to the dealer tomorrow unfortunately.
 
Is it engine oil or transmission fluid (oil) captured on the floor? At least for me, I find that the transmission oil is extremely pungent smell wise..

Perhaps take a shot and drain the transmission oil and measure the captured fluid; perhaps it is overfilled? Take the opportunity to replace it with new fluid, use the BMW recommended oil and measure it to the proper amount and see if your results change.

If the bike is still under warranty, perhaps see if the dealership will provide you the oil as it is expensive; or perhaps, have them do they're job and troubleshoot things properly..

I'm not sure how replacing the breather tube can fix anything that it is doing as designed, and how does a breather tube even break or fail..??
 
For sure transmission oil. Gear oil has a unique smell as you noted. It has less than 900 miles so very much under warranty (bought in Jan this year). Dropped it off again this morning.

They are either over filling it, didn’t install the vent correctly/damaged it during install, or there is an internal issue in the trans (missing baffle, etc). The vent was updated by BMW to a new P/N but unlikely the cause .
 
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