Looks like I may have the diff leak issue on the 04 Z. It doesn't seem to do it though when driving short distances, in fact I've driven it to work all last week and no drip. I've only noticed a drip or two after a long drive. I went up to Road Atlanta this past weekend (about 60-70 miles away) and when I got up there, I checked and there was a drip formation from the rear diff. I'm guessing the diff fluid is heating up enough to where it becomes thin enough to make it past the o-ring. The weird thing is that I wiped it off when I got to RA, but when I came back home, I checked again and no drips.

I checked all the bolts around the diff and they are tight and I've only noticed it within the past couple thousand miles (has just over 14K on it now). I've never had the diff fluid changed, so it was at the level from when it left the factory. Thought it may have been the vent tube on top, but if it was I would have noticed it a lot earlier than a couple thousand miles ago.

Like many of you, I dread taking it to the dealer, but I would rather have it fixed (still under warranty). How long does this procedure take? I would rather not leave it, so is this something that can be done in a day? Should I even mess with it if it doesn't happen all the time and just maybe swap out the diff fluid every 10-14k?

Thanks...

 

ONE DAY JOB.
DON'T LET THEM OVER FILL THE REAR.
Good luck.

 

Just for the record, I had the same problem on my 02 Z and had a shop drain and refill with RP Maxgear and have not had the problem since. I think mine was overfilled from the factory and only revealed itself after long drives or very spirited driving (usually on the long drives). Just my .02

Mike

 

Be careful not to mis-diagnose a leaky rear for a blocked off screen. My 03 had a dirty screen which I took for a genuine leak.

Cleaned the screen, wiped the old oil away, and now she's good to go.

Mark

 

Thanks for the responses guys...

Mark, what do you mean by blocked off screen?

 

There is a sort-of screen on the top of the differential.. I'm not too completely sure as to exactly why it's there, (I think it's there for aeration purposes) but there is a screen that gets clogged very easily.

When it clogs, and the pressure of the oil and differential raises, (from driving) that oil finds any exit that it can.

 

Wow, never knew there was a screen up there. I'm guessing you just have to feel around up there on top of the diff. Is it close to the vent? How is it held in place?

 

I've never actually seen it, but my understanding is that the screen IS the vent. If the vent gets clogged, pressure builds.

 

its probably just coming out the breather on top. mine did that after a 140mph run on a long straight highway. it was coming out of the breather on top. i was ready to replace the axle seals but decided to talk to a vette mechanic that i use for stuff that i won't tackle. he looked at it and told me it was the breather and that on c5's its right over the ring gear and at high speeds in a straight line it can leak out the breather. he was right. it hasn't leaked since and i would have sworn it was coming out the driver side seal. i'll bet many have been replaced needlessly because of this.

 

Thanks again for the responses. I may just keep an eye on it and actually been meaning to do a diff fluid change, so I'll see how much it's lost. Just strange that if it was overfilled at the factory, how come it took over 12k miles to finally be coming out of the vent.

Also, I do have a GMPP extended warranty for another year, so I got that going for me, which is nice...

 

My '04 Z started spewing diff fluid around 14k also. I was convinced the rear was leaking, but the stealer said it was coming out the breather. They attached a hose to the breather tube, ran it up inside the fender to provide some "breathing room", and it hasn't leaked since! You may wish to try this little mod on your own and see if that helps.

 

The DEALERSHIP did that?? Wow, that's actually pretty cool of them. Got any pics of the install?

 

I can feel the vent on top of the diff. It's almost like it's got this thimble like top that feels a little loose and spins freely. Are we all on the same page and there is not some other device that is the vent?

 

Sorry, no pics, but from what I understand they just attached the hose to the vent, ran it up in the fender for some height, and then wire-tied it in place. Pretty simple fix, and they said they've performed it dozens of times with good success.

 

I had a leak that got worse after 2 days HPDE3 at PIR(Phoenix). I took it to Darrell at Xtreme Motorsports.

He just called, said it was an O-ring. $180 plus fluids(redline) and I'm good to go. It's worth it because I did'nt have the time and I want to be ready for the next event!

Cheers from Arizona.