Venting Differential?

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Aug 28, 2006 | 01:53 AM

#21

ZeeOSix

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Joined: Mar 2002

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From: PNW

Quote:

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

Here's a test to help determine where the oil is coming from. Adjust level of differential to correct level when cold -- you've already done that. Clean ALL oil residue off differential, including vent area and side housings near axle seals. Drive the car for a few days, and then inspect all areas for oil residue.

If there is oil just below the vent area then the oil is puking from the vent and running down the side cover seam to the bottom of the side cover. If there is oil just below the area where the axles enter the side covers then it's the axel seals. If there is oil on the bottom of the side cover and all other areas are dry then it's most likely a bad side cover O-ring, which can take some time/mileage to show up. The O-ring probably gets hard with time and repeated hot/cold cycles and eventually starts leaking. I think GMs TSB for the differential side cover leak is to use a new O-ring and some RTV sealant on the side cover mating surfaces to cure this.

Yes, clean everything up and monitor it for a while is the best move at this point.

Aug 28, 2006 | 03:33 AM

#22

allmee

Racer

Joined: Dec 2005

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From: North Las Vegas Nevada

Quote:

Originally Posted by ZeeOSix

If you look under the rear of the car (just get down on your knees and gaze under it) and look at the BACK of the differential you will see the fill plug (which has a metal tag on it) over a few inches to the right side of center line. The bottom of the fill plug is about 1/2 to 3/4 inch below the bottom of the axle seals.

The point I am trying to make is, the fill hole is on A side of the rear end, if it is the back end, so be it, but it is still a side. But how do you go over that point to over fill it? Someone said that the rear end fluid is thick, like ice cream, and is easily overfilled due to that reason. I did not know this.

Aug 28, 2006 | 04:13 AM

#23

tstar

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Joined: May 2006

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From: DuBois PA

St. Jude Donor '11-'12-'13-'14-'15

My understanding of what’s going on here is that the fluid level should be checked HOT or NOT (Normal Operating Temp.). Either GM or GM’s better mechanics have basically revised its fill procedures and now recommends that the rear end level should be hot and fully expanded when it’s checked. If I’m not mistaken, Mr. Curlee chime in here please, you can fill it cold to a level approximately 1/8” below the fill plug and be right about there. Hope that clarifies things for ya…

Tim
99 Coupe

Aug 28, 2006 | 05:04 PM

#24

ZeeOSix

Le Mans Master

Joined: Mar 2002

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From: PNW

Quote:

Originally Posted by allmee

If the car isn't level (nose down some) when they fill the differential it would be easy to overfill it some. Guys who work on their cars at home might not have it jacked up level and the rear end might be up higher than the front. Since the fill hole is on the back of the differential, the oil level would be overfilled if the back end is jacked up too high and the level was brought up to the bottom of the fill hole.

At the dealer, if they use their filler gun and fill it real fast it's possible that it could be over filled some. They just pump it in fast until they see it coming out the fill hole, then slap the fill plug in as fast as they can. If they would let it drain for a while, I bet quite a bit would come out before finally stopped at the bottom of the fill hole.

Last edited by ZeeOSix; Aug 28, 2006 at 05:27 PM.

Aug 28, 2006 | 05:12 PM

#25

patton

Safety Car

Joined: Jun 2004

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From: panama city beach florida USA

St. Jude Donor '09

okay ice cream is bad . milk shake. right on the mark: fill it too fast and you will over fill it . 1/4 inch below fill hole and ya wont blow anything. while youre under there reach up and feel vent it should be loose [cap]

Aug 28, 2006 | 05:25 PM

#26

ZeeOSix

Le Mans Master

Joined: Mar 2002

Posts: 5,955

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From: PNW

Quote:

Originally Posted by patton

... while youre under there reach up and feel vent it should be loose [cap]

I can feel the spring action in the vent's cap ... but does that ensure that the vent is actually working correctly?

I'm not sure how the vent is designed, but it sounds like it is some kind of spring loaded valve that relieves when there is enough pressure inside the differential. If the valve is stuck, maybe it's still possible that the cap on the vent has the spring action to it - the valve seat could be stuck and not lift when there is a slight pressure on it.

I'd like to see a differential vent tore apart so I can see how it really works. Anyone see one off the car and examined how it operates?

Aug 28, 2006 | 06:20 PM

#27

allmee

Racer

Joined: Dec 2005

Posts: 431

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From: North Las Vegas Nevada

I appreciate all the feedback guys! Thanks

I think I will get under my car and check the level. If my end was overfilled, it may have pissed out enough oil to be at the right point. I drove today....ALOT in 105 degrees and no leaks that I saw.

Thanks again!

Rob

Aug 29, 2006 | 12:08 AM

#28

Dirty Howie

Team Owner

Joined: May 2004

Posts: 26,345

Likes: 232

From: SoCal

Quote:

Originally Posted by ZeeOSix

The fill plug doesn't vent ... there is a specific vent mechanism located at the very top left hand side of the differential’s main case.

Anyway, did the dealer replace the vent (since it sounds like it was defective) to cure the leakage on your car?

Sorry I meant to say that THE VENT was plugged causing excess pressure, thus leading to the leaking plate seal.....according to the dealer.