23K miles on an 03Z, left side diff leak just started. Previous threads mention the old-style seal as the usual culprit, but some have found overfilling and/or blocked vent as causes. Sure enough, when I removed the fill plug, pressure escaped along with a couple oz. of excess lube. Since then, the floor spotting has almost stopped.

The shop manual seems to show a vent on the top side of the diff but I can't find one. Where is it? Can it be removed without dropping the diff? If clogged, can it be cleaned out or would that be a replacement?

 

its supposed to there ive not seen it if its on the diff i,ll unwrap a spare rear and look mine had psi when checking it once i though that was a no no but mine doesnt leak. vent can be r+r ed and cleaned [usualy]

 

My 01 just started leaking again, for the 3rd time. Except, this time, it only leaks after a long highway drive, 30 miles or so. A shorter hway drive and around town......nothing! ??? I wonder if my rear end vent could be the culprit?

 

Run this by me again?

 

A read end that doesn't vent can be a problem..

Sorry, it's early....

Bob

 

I believe #8 is the vent:

http://home.woh.rr.com/mikemercury/pics/carrier1-sm.jpg

and I do believe it may be a one-way vent (not 100% certain). It will allow pressure to escape - but not vacuum. Was the noise you heard as the fill plug was removed - pressure... or vacuum ?

 

okay i just unwrapt my spare 01 rear the vent is on top of driver side out put shaft. it is a press fit i guess very hard to r+r in car. reach up and feel that the cap is free to move.a clogged vent will build up psi and find the weakest point to leak out . making a common misdiagnosis. an old 4 wheeler trick is to pop off the cap ,make sure the short tube is clear and put a piece of fuel hose 1 foot long with a loop in it and zip tie above. or crimp the cap back on after making sure it clear of course this assumes that you can access the thing in car. the other post question; i think it was psi i got a faceful when i pull the fill plug. again mine has not ever leaked i,m at 110000 k

 

Yes on #8.
If you overfill it will blow excess out of the vent till it finds its level. I suppose it could be clogged but while you can feel the vent I doubt you could remove or clean it with diff in place.

 

While having my 04 serviced I sneaked under and found oil on my exhaust. The area is on the passenger side just before the upward bend and mostly on that side of the chunk. There was a tube leading from the vent down just above the output cover. The tech said they have a GM Letter to re-seal all output cover with anaerobic sealant. It looked, very much to me, like it could be, that the leak came from over-filling. We have an appointment with the Vette Tech on 7/24/06, and I hope they will let me look, for my self distrusting sake, before I let them do the repair. From what I read here I'm wondering if GM has a fix for this problem. Does it require, such, a high oil level to lube, that it will travel up to the vent and over time clogs it and pressurize the chunk then blow the seal? May be its a metal casting, or a thermal stress problem and the surfaces don't fit-up properly or expand differentially as the chunk heats up. The Vette Tech cleaned the chunk topped if off. I have driven the car, daily for 6 weeks, a lot longer than I should have, so as to create and expose a fresh chunk blood trail for him to follow. I will post what they find and Do To Fix The Leak.
Trb

 

In the service manual, under rear end leaks, it lists one of the first causes- a plugged or non functioning vent valve. But it says nothing about where it is located, or how to go about checking it or replacing it. Amazing!! I am gonna get under the ride in the next couple of days. Anybody can tell me what to check for? I saw in a post that it is on the drivers side and on top of the housing.

Any help is much appreciated!!

Grazie!

 

Upper right corner of the diff. Driver side.



And a close view

 

You are the BOMB!! Thanks so much! Does that cover on top need to be loose in some way?

 

Mike, Patton, 747:

Thanks for the excellent info. You've confirmed my sense that the vent would be dang near inaccessible with the diff in the car.

My first thought when the leak started was that this is the time to do the DTE diff upgrade, strut and clutch. Even got a calendar slot at CAM for the work. But, assuming the leak doesn't start up again, I believe I'll just check for more pressure buildup in a month or so, and postpone that $5K outllay.

 

My rear didn't start until I hit 11,000 miles. I always check under the car for leaks and read every post I can here. One post I read said to check the bolts on the drivers side cover, I found three loose. I tightened them, checked the vent and so far so good.

 

the cap on top it supposed to be loose. if you would find it stuck and free it up you may not yet be free and clear of psi build up. the tube still could be clogged. i havent tried to look at it in the car but it looks hart to pull it maybe pry cap off and poke a wire through then crimp cap a tad and reinstall

 

Mine has leaked 6 different times. The last was last year when, while we had it apart, we changed the vent. Two weeks ago, I found a fresh drop. I read some where about Red line diff lube. It's states that it lowers the temperature inside the case and does not need the additional gear lube. Installed it two weeks ago, and so far, no more oil on rear diff. I can't say that this is the cure, but it can't hurt.

 

Mike is exactly right on these vents. They are a one-way valve that lets air out of the case but not back in. At least on a 01 Z06 anyway. When you loosen the plug you hear it hissing, but what your hearing is air going into the case, not out. Unless you drive you vette in the mud like a off roader or drive on a lot of dirt roads, or just have a LOT of miles on your car I very seriously have a clogged vent. With exceptions of 4WD trucks, I have only see one or two clogged vents in my lifetime.

 

My last repair (2nd) of the side leaky plate by the dealer was necessary according to them because the vent was plugged......they replaced the vent system. This is a Z06 differential......


DH

 

Those are the key words!!!

When I pulled my diff to install the output shaft I heard the same air rushing into the case when I drained the oil and I thought the vent was clogged. When I turned the case upside down and no oil ran out the vent I thought the vent was clogged. After I got the diff apart and tried to spray brake cleaner through the vent and it didn't go I thought the vent was clogged. And until I got the air hose and rubber tipped nozzle and blew air through the vent did I realize the vent was in no way clogged and that it in fact was a spring load valve inside the vent. I'm guessing 95% of the people (including dealers) who hear that hissing when they screw out the plug is going to think that is air blowing out of the case and the vent is clogged, when in fact it is air being sucked into the case and that is the way the vent is designed.

 

and that can sound almost exactly like escaping air.