Venting Differential?
Thread Starter
Intermediate
Joined: Jun 2006
Posts: 30
Likes: 0
From: Nashville TN
Venting Differential?
I was under my 2002 Z06 checking it out and noticed that there a few drops of yellow oil on the bottom of the differential and oil running down the driver side of the differential. I thought that it might be one of the side seals throwing oil around (seen a lot of posts about this) but they both are completely dry. I have read about oil leaking out of the differential vent when the car is driven hard and there does seem to be oil around there but I can't really tell where it is coming from for sure.
I have been known the let Z06 be a Z06 from time to time. I think the guy that owned it before me probably completely babied it. Given that the car has about 7k on it does it make since that it has not had that much pressure in the rear-end before and vented oil? I am pretty sure the fluid has not been changed before so I doubt it was over filled.
What do you think? Should I have it checked out for a leaky gasket or just clean it up and see if it happens again. I can’t really tell what is happening and don’t know how common it is for the differential to vent oil.
I have been known the let Z06 be a Z06 from time to time. I think the guy that owned it before me probably completely babied it. Given that the car has about 7k on it does it make since that it has not had that much pressure in the rear-end before and vented oil? I am pretty sure the fluid has not been changed before so I doubt it was over filled.
What do you think? Should I have it checked out for a leaky gasket or just clean it up and see if it happens again. I can’t really tell what is happening and don’t know how common it is for the differential to vent oil.
Racer
Joined: Mar 2006
Posts: 265
Likes: 3
From: Metamora, IL
I agree with Bill, but you should check the oil level while you are under there. Just pull the fill plug with the car level. If oil runs out, let if flow until it quits (cold of course) and you have it at the proper level. If there is no oil when you remove the plug, stick your finger in there to use as a gauge. If it is within about a 1/4 inch or so from the top, it is OK, if not, you should add some to bring it to the level of the fill plug. Good luck!
Safety Car
Joined: Jun 2004
Posts: 3,500
Likes: 702
From: panama city beach florida USA
St. Jude Donor '09
there could be issue with the vent . ive seen 3 with presure in the diff after 5 mins. of shut down. the first time it got me in the kisser. a tip on leaks on auto they tend to go down and to the rear.were you see it aint were its leaking. as for the vent its pressed in the cap can be pried of there is a weak spring and flat rubber washer. its hard to believe it would hold psi but it does .
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
i was told by C4,C5,C6 mechanic yesterday that we should be checking the rear end fluid HOT as it makes a difference in the correct level. If you pull the fill plug and you have pressure, or no vacuum, there could be an issue with the vent or a seal.
BC
BC
Melting Slicks
Joined: Aug 2005
Posts: 2,252
Likes: 0
From: NH
I had some minor leaking with my '03 Z06 and had my dealer check it when I took it in for an oil change. They drained a half cup or so out of the diff. and no more problems. Oil will run out of the breather during hard acceleration.
Burning Brakes
Joined: Jan 2002
Posts: 935
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From: Trumbull CT.
If you are sure the fluid has not been changed it does not mean it is not overfull. Mine had not been changed and did not become a problem until after 11,000 miles. I pulled the fill plug and found it was overfull by 4-5 ounces. If you pull the plug try to get a bottle under the fill plug or you may have a mess back there. My $.02.
Racer
Joined: Dec 2005
Posts: 431
Likes: 0
From: North Las Vegas Nevada
My car has been leaking only after a long drive in the middle of the hot day, here in Vegas, and the rear end has gotten good and hot. I was thinking that the vent may be plugged and the pressure build up is pushing fluid past a gasket. Now I am starting to wonder if the rear may have been over filled, when my side seal was last done in Sep of 05. But how do you over fill the rear end when you are supposed to fill it up to the bottom of the fill hole? You can't go any higher than that if you wanted to, being that the fill hole is on the side of the unit! I am curious
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Racer
Joined: Jul 2006
Posts: 385
Likes: 1
From: Chapel Hill North Carolina
If you overfill the diff it will come out the vent tube. If it is that no problem. Also there has been some TSB on the diff leaking on the driver side. Did the previous owner have any work done regarding that?
Burning Brakes
Joined: Jan 2002
Posts: 935
Likes: 0
From: Trumbull CT.
Originally Posted by allmee
My car has been leaking only after a long drive in the middle of the hot day, here in Vegas, and the rear end has gotten good and hot. I was thinking that the vent may be plugged and the pressure build up is pushing fluid past a gasket. Now I am starting to wonder if the rear may have been over filled, when my side seal was last done in Sep of 05. But how do you over fill the rear end when you are supposed to fill it up to the bottom of the fill hole? You can't go any higher than that if you wanted to, being that the fill hole is on the side of the unit! I am curious
Racer
Joined: Nov 2005
Posts: 287
Likes: 12
From: Toronto Ontario
Originally Posted by Bill Curlee
i was told by C4,C5,C6 mechanic yesterday that we should be checking the rear end fluid HOT as it makes a difference in the correct level. If you pull the fill plug and you have pressure, or no vacuum, there could be an issue with the vent or a seal.
BC
BC
Maybe we can get C4,C5,C6 mechanic to tell us where he found the info re checking the rear end fluids HOT.
My 2003 service manual says,
"Inspect the the transmission fluid level, ensure that the fluid level is even with the bottom of fill plug hole."
Re rear drive axle "Check the fluid level to ensure it is even with the bottom of the fill plug hole to no lower than 6 mm (0.25in) below the opening."
In both cases no discussion of HOT. We need to know the proper procedure. HOT or COLD?
Team Owner
Joined: Apr 2001
Posts: 54,204
Likes: 180
From: S.W. Ohio. . . . . . NRA Life Member
Originally Posted by Roadking
If you are sure the fluid has not been changed
The fluid iteslf is clear, but the breakin grease that Getrag uses is green... so it all gets mixed together after the car gets driven and the fluid then sports a green tint to it..
Thread Starter
Intermediate
Joined: Jun 2006
Posts: 30
Likes: 0
From: Nashville TN
It looks like the factory probably over filled the differential. I removed the fill plug with the car level and a fair amount of fluid came out. It did have a green tint. I’m going to check it again in a week and to see if there is more oil on the housing but I think that was the problem. It sure beats a bad seal.
Thanks for the help.
Roger
Thanks for the help.
Roger
Advanced
Joined: Jul 2006
Posts: 67
Likes: 0
From: Phoenix AZ
leaking diff
Another shining example of poor engineering
I gave up on mine and let it leak... (very much like a 74 Chevy Vega I owned as a kid) 30 years and GM cant stop oil from leaking between 2 pieces of metal
Glad Vettes look as good as they do
Its the only reason I own one
I gave up on mine and let it leak... (very much like a 74 Chevy Vega I owned as a kid) 30 years and GM cant stop oil from leaking between 2 pieces of metal Glad Vettes look as good as they do Its the only reason I own one
Team Owner
Joined: May 2004
Posts: 26,345
Likes: 231
From: SoCal
Originally Posted by rogerdahlman
It looks like the factory probably over filled the differential. I removed the fill plug with the car level and a fair amount of fluid came out. It did have a green tint. I’m going to check it again in a week and to see if there is more oil on the housing but I think that was the problem. It sure beats a bad seal.
Thanks for the help.
Roger
Thanks for the help.
Roger
My last left side diff leak was a result of the fill plug not venting.
DH
Racer
Joined: Dec 2005
Posts: 431
Likes: 0
From: North Las Vegas Nevada
Originally Posted by Roadking
Last I knew the tranny fill was on the side and the differential fill was at the rear of the unit.
Is the oil that thick as stated?
Racer
Joined: Dec 2005
Posts: 431
Likes: 0
From: North Las Vegas Nevada
Originally Posted by Silver Z06 Driver
Another shining example of poor engineering I gave up on mine and let it leak... (very much like a 74 Chevy Vega I owned as a kid) 30 years and GM cant stop oil from leaking between 2 pieces of metal Glad Vettes look as good as they do Its the only reason I own one
I gave up on mine and let it leak... (very much like a 74 Chevy Vega I owned as a kid) 30 years and GM cant stop oil from leaking between 2 pieces of metal Glad Vettes look as good as they do Its the only reason I own one
But you gotta admit, the car does run pretty good too 
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Originally Posted by Dirty Howie
My last left side diff leak was a result of the fill plug not venting.
Anyway, did the dealer replace the vent (since it sounds like it was defective) to cure the leakage on your car?
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Originally Posted by allmee
What I am getting at is the fact that the fill hole is on A side! Not the top of the unit, where overfilling would be more easily done.