I just took my newly aquired '03 AE automatic Coupe on it's first extended road trip. The car has 10,000 miles on it and I drove about 100 miles on the interstate to my daughter's home. When I got there I was shocked to find the rear of the car up to the tailights had a fine oil film on it. I checked under the car and there was nothing dripping at the moment but after 2 hours there were several small quarter-size drips on a newspaper that I put under the differential of the car. The rear of the differential on the driver's side was oily and the wiring loom on that side was also oily.
I wiped the film off and decided it was OK to drive it home. I stopped twice on the way home and checked and no oily film or drips.
I just had the car in for it's first service last month, an oil change and flush/replace the brake fluid. I was under the car when it was serviced and it was clean and dry with no signs of any leaks.
Any help would be appreciated.

 

very normal. the left side differential leaks like a sponge. design flaw.

 

More than likely it's the differential axle seal GM part #88996703
Cost for the seal at the dealership is approximately $30.

Find a good (C/5) specialist in the area (not dealership)
Time to repair would be approximately 1-4 hrs.
Cost would be approximately $150 to $400. part/labor.
A good C/5 specialist will be able to do this job without removing/dropping the cradle., which saves alot of time.
Good luck.

 

Thanks...Any chance that it is the differential vent? I did a search and found some owners with the vent blowing oil when it got hot after a long high speed trip. All my trips have been local and the previous owner only drove it on short trips also.
Is it safe to drive if it's not leaking now?
Guess I won't know for sure until I get it on a lift...

 

Well let's figure things out.
If you have a manual shift, there would have more stress/shock to your complete drive train, to include the axle seal.
If there has ever been "wheel hop", would also cause stress/leak.
Age & miles of car makes a difference.
I believe you mentioed that you have had the car serviced recently?
Surely they could/should have done a differential fluid level check at that time.
Chances of the vent being clogged is slim, but of course a possibilty.
If there is oil all around that drivers side axle seal (where the short haft comes directly out of the differential) More chances than not it is the differential axle seal.
Being that the fluid hasn't been checked & you are not capable of doing so?.. I would have it checked before hardly any more driving on it.
Good luck.

 

Just an update. I jacked up the car and removed the LR wheel to investigate and found the top of the differential wet around the breather vent.
No indication that the rear seal or side cover was leaking. Everything I saw indicates that the leak came from the breather venting excessive pressure from the diff during my ride last Sunday.
I cleaned the diff, crossmember and wiring coil and have the car scheduled to be checked by a local Corvette mechanic to confirm my findings.
I'll have it out again this weekend (weather permitting) and plan to check the rear diff level when the car has been driven for a while.
I hope that the "burp" of fluid that occurred last weekend was enough to bring the level to where it should be.
As many other posters have documented, they felt that their cars were overfilled from the factory and vented excess fluid when driven the rear end heated up.
I'll join the thousands of other Vette owners who voice their disappointment with GM for not correcting the design problem with the vents/seals.
Expensive car...poor design of basic system.

 

All differentials from all car manufacturers will have a vent and use lip seals around the axle shafts. A lip seal is a wear item and has to be replaced over time. My C5 has 237,000 miles on it. I replaced the differential seals one time when I had it apart to replaced the left side stub shaft that I broke at the dragstrip. So what exactly is the design "flaw" again?

 

 

There is nothing unique with the vent system on the Corvette differential. Over serviced differentials can be an issue and in most if not all cases happens after it leaves the factory. It is common for the unknowing to jack the back of the Corvette to service the differential and not take into account that the vehicle is not level and fill the diff until it flows out the fill hole.

As others have already pointed out, there was an issue with some of the output shaft seals. They have been superseded with an improved one. There can also be some seeping from the driver’s side differential cover. The fix is a new o’ring and a good flange type sealant.

 

A friend has a 4X4 Chevy truck, only a few years old and not high miles, that he wanted me to go through, changing fluids and etc.. No one had touched the truck out of the factory except for oil changes.

When I got to the transfer case, I located the drain and fill plugs and figured I'd pull the fill plug first to promote drainage. I positioned a pan underneath in case there was a trickle once I removed the fill plug and started turning a wrench. Once the plug was loose, I continued turning by hand.

The plug got that "loose" feel you get when there is only a turn or two left so I knew I was close. I gave it about another millimeter of turn and the plug shot straight out of the case and pinged off a crossmember, followed instantly by a jet of gear lube that just kept coming and coming. The same crossmember that the plug hit deflected lots of the lube everywhere and my face and head caught a pint or two of it. That was a fun clean-up, me and the driveway.

Since the guy swore that the truck had never had the transfer case serviced, and since the plug and the case area surrounding it looked untouched to me, I can only assume the factory SOMEHOW managed to double-fill it (there was at least twice the factory-recommended amount of lube in the case, 'tho so much avoided the pan that I don't know exactly how much was in it). Was surprised the transfer case didn't blow seals, vent or leak lube or something, but I don't know that he ever even engaged 4-wheel drive on the thing.

 

this would be that design flaw thing i was talking about. very common on the C5 also known as the leaky butt syndrome. all over this forum. so yeah design flaw.