Front diff breather spitting oil

[56napco]

I couldn't find anything searching this forum and tried another GM Truck forum with no luck either.
I have a 2002 GMC Yukon XL 2500 SLT, 6.0L. I've been noticing that after driving highway speeds, 70 to 75 mph, there is oil dripping off the frame and the front differential breather is wet and oily. This is the only oil leak on this truck. I've taken the breather out of the differential, cleaned the hose and checked for any blockages. The breather is positioned straight up, not laying on the frame. Has anyone had this happen before? I haven't changed the fluid in the front differential either.
Thanks

 

[OR VietVet]

Well now is the time to change that fluid. You need to look inside that housing and check to make sure all the breather access is clear.

 

[56napco]

I have taken the breather out of the differential already. Large plastic piece that threads into the housing- Blew compressed air through it and brake cleaner and the breather assembly was clear and free flowing.
Changing the fluid is on my list of things to do, as far as I know it is still factory fill.

 

[afpj]

We have 02 5.3L Yukon std (not 2500). Noticed in the past that leaking some front diff oil from the black vent hose that lays on the inner fender on driver's side. Same situation (after freeway driving in summer) The hose has a black vent cap on it, but the hose was bent over so the black vent cap was facing down. After I rerouted the hose and secured it so that the black vent cap end is just sticking straight up, the leaking went away. I'm thinking that ventilation was not being provided properly with that hose bent over. Perhaps your issue may be as simple. It wouldn't hurt to change the diff fluid anyway and check the condition. I'm assumingwhat you're referring to in the forst post is the vent cover seal?, not the one on the end of the black hose that I am referring to. Good luck

 

[OR VietVet]

He said the hose and vent were positioned straight up. Otherwise I too would have suggested to inspect for a kink. Still say that he should change fluid and I think he said he would.

 

[livingez_123]

Change the Effing oil! oil has an anti-foaming additive in it.....it stops working after years of use.

 

[OR VietVet]

Change the Effing oil! oil has an anti-foaming additive in it.....it stops working after years of use.

Thanks for the input. Couldn't have done it without you!

 

[afpj]

He said the hose and vent were positioned straight up. Otherwise I too would have suggested to inspect for a kink. Still say that he should change fluid and I think he said he would.

Got it... wasn't sure when OP said "took breather out of differential" he was referring to the vent cover seal as I've read those leak too. Didn't know about the antifoam stuff. Good info. Even old farts can learn still.

 

[livingez_123]

oil just isn't oil. every mfg has their own "additive package" the put in the oil. from cleaners to anit-foam agents and even viscosity improvers. with time, it all breaks down back to the base stock. You can take the old oil, filter it, reintroduce the additives and sell it again. I know it's more involved than that, but you get the idea. even the synthetic oils break down over time.

 

[56napco]

Yes, the breather is pointing straight up near the inner fender. I removed the entire breather assembly to clean and inspect it. I took the large plastic threaded part out of the housing and checked that for blockage and to make sure the metal part that keeps oil from being thrown into the breather port on the inside had free movement as well. The breather hose also has no blockages or kinks. I was basically trying to find out if any other people have had issues with this and what was found to be the issue.
Also, the front driveshaft will not freely spin in 2HI and is always engaged. With the Auto 4x4 transfer case I've read this is normal.

Thanks for the thoughtful and insightful information regarding the oil- I'm well aware oil breaks down over time and doesn't last forever. I am going to change it as I stated in the initial post, it just hasn't happened yet since other events in life have gotten in the way. I am skeptical this fixes the issue but it's going to get changed regardless. I have other GM trucks with more miles than this Yukon (250,000+) not listed in my signature with the original oil in the differentials and none of them puke out of the breather.