[Jegs87trx350]

Hey everyone! I went for a pretty long ride today but had to cut it short because I thought my oil cooler, or the left hand oil hose was leaking. There was enough drops of oil to make me concerned. Upon getting home I removed the left hand mud shield and much to my surprise the oil was coming out of one of the breather hoses right there up high next to the frame. Crank case breather hose? Anyone have any idea why that would happen? I was cruising right along when it happened. Going about 30-32mph. Not sure what that translates to In rpm's but I'm guessing near 4000? And thoughts wold be much appreciated as I had a long ride with my girlfriend planned for this saturday. Thanks!

 

[retro]

Is it the fat hose that hangs in the top frame rail on the righthand side? That fat one goes down toward the cross frame under the seat to a T, then one hose from that T loops over the frame thru a holder clamp and plugs into the top of the motor next to the chain tensioner... the other hose from that T goes down to a swingarm loop where its capped with a one-way drain valve... Is that vent tube assembly the one you are referring to?

 

[Jegs87trx350]

Yes I believe that is the one. Has to be ,right? With oil coming out of it? The fat line I believe travels up the right hand side frame and then crosses over and changes to a smaller one before terminating on the left hand side as viewed from sitting on the wheeler. Do I have that correct? After I write this im gonna go take some plastic off to be sure. Why would oil be coming out of it though? The oil level was perfect by the way. Not overfilled at all.

 

[Jegs87trx350]

Sorry I was wrong. I apologize. I should've looked before posting... it is not the large hose. It's a smaller one on the left side frame. I'm going to go trace it now. I just wanted to correct myself. Thanks.

 

[retro]

Yeah thats gotta be the one. My machine may be plumbed different than yours but it sounds like we're on the same page. First thing I would do is unhook the hose from the motor and rev it a bit to see if its blowing a lot of air/oil mist out of there or not. If it looks excessive then its time to troubleshoot the motor for the reason...

Edit:
Oops, we were posting at the same time, sorry 'bout that. I type pretty slow as you can probably tell...

 

[Jegs87trx350]

I think I was mistaken thinking it was oil. I believe it is instead rear differential fluid. It's hard to tell by smell, I don't smell very good and I checked the diff fluid in the rear and it is full. I smelled it and to me it smells similar to oil. That is the only thing it can be after tracing it back. I guess that rear diff doesn't like going that fast! Lol. I'm not going to close the book on it yet but that's where I am so far and just wanted to post back. Thank you for your replies!

 

[shadetree]

I think I was mistaken thinking it was oil. I believe it is instead rear differential fluid. It's hard to tell by smell, I don't smell very good and I checked the diff fluid in the rear and it is full. I smelled it and to me it smells similar to oil. That is the only thing it can be after tracing it back. I guess that rear diff doesn't like going that fast! Lol. I'm not going to close the book on it yet but that's where I am so far and just wanted to post back. Thank you for your replies!

rear differential can have water mixed in, be too full, this would cause your issue.

 

[retro]

Is the rear diff vent hose hose hung up high under the steering head where it belongs? If that happened to me I'd be keeping an eye on the oil level in the rearend in case a pinion seal is going out or something... seems like if it can vent oil way up high, then its possible that air is getting whipped into the oil making it foam up..? Maybe its just cause you were going fast and warmed it up... like you said.

Is the viscosity of the oil pretty close to 80w that you have in it now? Anyway, glad ya got a handle on it...

 

[Jegs87trx350]

Well im positive that it is diff fluid now. Would it only leak when driving real fast though? It did it to me awhile ago, before I re-sealed the valve cover, but I just assumed it was oil that had leaked from the valve cover. And, in your opinion, would diff fluid come out like that if there wasn't water in it? I guess I should change it!

 

[Jegs87trx350]

Yes the diff breather is hung up high where it should be. It has straight 90w fluid in the rear but 90/140 in front. I had to do that in the front to resolve a binding/chattering/horrible problem in the front diff. That was actually the reason I joined this forum! It worked like a charm and I haven't had one problem with the front diff since I did that. I will drain/refill and keep an eye on the fluid level for sure.

 

[retro]

Oh yeah... I remember your front diff problem from a while back now... I think I have that thread bookmarked somewhere, cause I'm interested in finding out why that happened and why the thick oil fixed it, some day. After your thread I almost took my front diff apart to have a looksee... but I don't have all the right tools to complete the job so its back on the watch list. Let us know if you learn anymore.... thanks.

 

[Jegs87trx350]

My theory was that the clutches were sticking together for some reason with the 90w and the heavier oil stays thicker and doesn't let them grab eachother?? Because it wouldn't do it when cold. I first put some friction modifier in and that almost fixed it which led me to try the heavier fluid. It was sending shockwaves all through my divertrain and making me think it was my front driveshaft! So now I have a spare set of cv shafts and an extra front driveshaft for someday. I'm slowly but surely collecting parts... Would there have to be water mixed with the diff fluid to make it come out the breather tube like that? I mean that's a long way to travel! Uphill the whole way too!

 

[retro]

Yeah I'm wondering the same thing... don't know why it would go that high if everything is normal. Stranger things have happened though...