Silverado 5.3 oil leak...Help to identify please.

[FADEC]

Hello, Have a 2002 Silverado 5.3 4X4 extended cab that I have owned since new. Has been gently driven and only synthetic oil every 5-6k. This weekend after towing some moderate cargo on a trailer up some long interstate hills (I68 from WV into Maryland), engine was worked pretty good. After sitting all night I now have a leak about as big as a saucer under the transfer case. Can't tell if it's oil, tranny fluid, or transfer case fluid. It does come from what does look to be a rubber vent hose that exit's just above the transfer case,the oil then dribbles down over transfer case. Seems like this hose runs forward over the top of tranny up by the bell housing, where I loose track of it. Anyone have any idea what this hose connects to and why it might be leaking??
I have never had ANY leaks or trouble with this truck. Don't think its tranny fluid as it doesn't seem to have that smell. Thanks, Tom

 

[StormRider]

Has the transfer case been serviced recently? If the oil is coming from the transfer case vent it may have been overserviced and the heavy driving up hills caused the venting of the rest of the fluid. It may just be a transient condition due to the heavy driving conditions..(I drove on I68 once to save 5 bucks on the PA turnpike, I probably burned more than 5 bucks in additional gas driving up those hills..)

Check the fluid level in the T-case. If its an Auto-trac case, it takes special fluid that may not smell like ATF or engine oil.

 

[FADEC]

It's an auto trac case, but nothing has been serviced. Oil has approx. 2k since last change. Don't have truck with me now to inspect further. Fluid is definately coming from rubber hose (I assume a vent hose) on top of transfer case. What is the purpose of this hose????? Maybe it was attached to a fitting somewhere up there and came off?? Tom

 

[Jim 5]

Can you use a zip tie to attach a little bottle or even a good quality ziplock bag to the vent tube?

If you can't positively ID where the fluid is coming from this will help. If it's bright red, then it's trans fluid.

You probably have the 4L60E transmission, and if you were towing in OD and not in 3rd, your torque converter could have been running unlocked depending upon engine speed. If that was the case, you could have significantly elevated your trans temp causing it to flow out the vent tube. That would be my guess, but you need to find out what fluid we're dealing with here.

If it's trans fluid, I'd change it out, look at an auxilliary cooler and make sure you don't tow in OD.

 

[FADEC]

Originally Posted By: Jim 5
Can you use a zip tie to attach a little bottle or even a good quality ziplock bag to the vent tube?

If you can't positively ID where the fluid is coming from this will help. If it's bright red, then it's trans fluid.

You probably have the 4L60E transmission, and if you were towing in OD and not in 3rd, your torque converter could have been running unlocked depending upon engine speed. If that was the case, you could have significantly elevated your trans temp causing it to flow out the vent tube. That would be my guess, but you need to find out what fluid we're dealing with here.

If it's trans fluid, I'd change it out, look at an auxilliary cooler and make sure you don't tow in OD.


Thanks for all the posts and good ideas. Since I don't have the truck with me now..it's in Va, I can't look at it a little more deeper. I would love to have someone with the same set up as me look above their transfer case and see it they have the same hose, and where it goes to. I towed mainly in 3rd with OD on some flat sections of road..maybe the trans temp were elevated..it was in the low 90's ambient temp. I believe I do have an Aux trans cooler as part of the trailer tow/Z71 package. Tom

 

[Jim 5]

I used to have that set up on my 04 Avalanche and would gladly have helped!

Sorry I can't help.