I have an 04 Bruin 350 2wd that has begun to leak gear oil / diff oil from the rubber boot that connects the rear arm and tranny. I am positive it is gear oil and not engine oil. Checked the filler cap on the diff and it was bone dry. Any suggestions or ideas. I cannot believe this is happening. I have two Bruins and the one I abuse has no problems. This Bruin is babied and is leaking gear oil. I can send photos up if needed. Any help is appreciated.

 

Is this the joint where the drive shaft goes into the back of the motor?
Thats along way for the oil to migrate..from the diff.
Theres some seals on both ends of the drive shaft, one in the middle gear and one at the diff. If its diff fluid, then thats the seal that needs fixing.
I cant get a link to work, but go here http://parts.yamaha-motor.com/
and look up the driveshaft and middle gear, and youll see the parts break down, and the seals. It will also give you the parts numbers.
If you look at the middle gear, it looks like the seal, #13, is actually at the aft side of that rubber boot.
Is there any warrentee left on this?

 

I also thought that was a long way for diff oil to be migrating. Engine oil levels are good and the leaking fluid does not smell like engine oil. I think if it was the #13 seal on the middle gear then I would be leaking engine oil. Maybe it is the #12 seal on the driveshaft. What do you think?

Next problem ... I have no idea how to access that seal on the diff. It looks like I may have to do some major disassembling to get to that point.

 

Rear end lube is gonna have a stinky sulfur smell.
Id refill the diff, and stay away from deep water for awhile, til it got fixed. See how much and how fast it leaks out, and while youre doing that, get a service manual. It will show the procedure for getting at things. heres one on ebay ebay