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Rear Oil Leak

69/99

Member
Joined
Apr 18, 2002
Messages
23
Location
Bridgewater, NJ, USA
Corvette
1969 coupe, 1999 convertible, 2018 Z06
I have noticed that after parking my 99 Vette in the garage there is a slight oil leak coming from the rear of the car. I also noticed some oil mist on the tail of the car after taking on the highway for a cruise. Has anyone experienced this same problem. If so, what did you do to resolve it? My car only has 10500 miles on it and it seems premature for an oil seal to start leaking.
 

c4c5specialist

Technical Advisor
Joined
May 29, 2001
Messages
3,682
Location
New Haven, Ct. USA
Corvette
Nope, but someday.
Hi there,
I would think, due to the spatter on the back of the car, that you were on the highway for a period of time.
It is possible that the differential or the transmission was overfilled.
I would confirm correct fluid level before thinking seals.
Most 'seal leakage' is traced to overfilled fluid level, that, when hot, overflow the vents.
Please keep us posted, c4c5:hb
 

69/99

Member
Joined
Apr 18, 2002
Messages
23
Location
Bridgewater, NJ, USA
Corvette
1969 coupe, 1999 convertible, 2018 Z06
Thanks for the info. I believe it is definitely the differential due to the greenish color and heavy consistancy of the oil. Could you please tell me how I can check the differential oil level? Where is the fill plug located? You also mentioned a breather tube. Where is this located? Any assistance you could provide me is greatly appreciated.
 
J

John L

Guest
I experienced a similar problem not long ago. Noticed oil on my garage floor after backing out one morning. It was the day after I'd had the car in to the dealer for an oil and filter change. Turned out (after I took it back to them) that they had overfilled the differential while performing routine maintenance checks. They cleaned all of the excess oil off the underside of the car and asked me to clean my garage floor and keep an eye on it. Haven't noticed a thing since and have had no more oil spots on the floor.
 

c4c5specialist

Technical Advisor
Joined
May 29, 2001
Messages
3,682
Location
New Haven, Ct. USA
Corvette
Nope, but someday.
H Ithere,
The vent for the diff is on the drivers side.
To check your fluid level correctly, please check the level before you drive the vehicle.
To correctly check the fluid level, please have the vehicle on a level surface. Next, use a 10mm hex bit socket, and remove the fill plug, located at the rear of the differential, on the passenger side.
The level should be just to the bottom of the fill hole, so that just a drop or 2 come out, if you have alot coming out of the fill hole, it was too full.
Please keep us posted, c4c5:hb
 

69/99

Member
Joined
Apr 18, 2002
Messages
23
Location
Bridgewater, NJ, USA
Corvette
1969 coupe, 1999 convertible, 2018 Z06
Thanks c4c5 and John L for your information. I will check the oil level the first chance I get and let you know how I made out.
 
M

Mark75

Guest
I also have a 99, and had the same problem just 2 weeks ago. I noticed a grayish green fluid on my floor in line with the rear wheels and in the middle of the car. I took the car to the dealer and was told it was the output shaft seal was bad. They ended up replacing 4 seals: (1) Seal 4.176 B, (1) Seal 5.508 B, (2) Seal 5.430 A.

I have the extended warranty and it didn't cost a dime. That was the best investment I've made in the last 3 years.
 

69/99

Member
Joined
Apr 18, 2002
Messages
23
Location
Bridgewater, NJ, USA
Corvette
1969 coupe, 1999 convertible, 2018 Z06
Did your rear start leaking just after you had the car serviced? Also, how long did it take them to change the seals? How many miles do you have on your car?
 
M

Mark75

Guest
I change the oil and other fluids myself, so nothing was overfilled. The dealer had the car over night because they didn't have all the seals in stock, otherwise it would have been done in less than a day. I have 21K on it.
 
R

RedRocket

Guest
I have a 99 and have noticed exactly the same problem. Oil splatter on the rear and a small oil spot on the garage floor. Guess I need to jack it up and take a look.
 
S

sqvvcd

Guest
69/99

I've seen many posting of this issue from others, and personally have this issue myself.

Around 28K on my car when I noticed the leak right at the center of the cross frame at the rear. Since the car never had to go back to the dealer since I bought new, I brought it in while under warranty.

The dealer told me that it is common on these C5, varies on mileage of the cars. They either leak or will never leak (whatever that meant). What they did for me was to clean it up, sprayed the rear with tracing powder and come back in a week or so.

Well, the end results was that the seal on the driver's side shaft went bad and that was where it was leaking.

This is an expensive unit to replace, have the dealers look at it if it is under warranty. If the rear unit poops out because lack of fluid, you will be looking at approx. $1800 to replace.

Best of luck
 

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