My new-to-me 2002 coupe with 13K miles appears to have some fairly minor lubricant seepage on the left side of the differential where the axle shaft connects - the classic leak discussed at length on this forum. The seepage appears to be minor - not enough to make a drip, just enough to attract some dirt and leave my fingers a bit oily when I grope around. Should this be a major concern for a weekend driven car? Is this something that should be a priority repair before I invest more money into the car? Thanks for your $0.02

 

The very first thing you should do is check the fluid level. It might be as simple as someone may have over serviced the diff with fluid. Also make sure the vent is clear. If the vent is blocked the diff can build internal pressure when the temp increases forcing fluid out the seal.

If all this checks out, if it were mine, I'd fix it. In fact my C5 had this leak when I bought it. It was one of the first repairs I made on it. Total cost for parts and fluid around $50 and about two hours to correct. I would suggest replacing both the shaft seal and the side cover o-ring. Both are known to leak.

 

My 03 seeped like that and I had it repaired under warranty. If it started doing the same thing again I would just let it seep and just check the fluid periodically to make sure it didn't get too low. At the seepage rate I was getting it would have probably taken a couple years for the level to drop a noticeable amount. Its just one of those things that a lot of people overreact to. If it isn't leaking badly you take a risk of screwing up something if you fix it. Its in a who cares place on the car. I couldn't see my leak unless I was under the car.

Bill

 

Like most all things mechanical, the leak will either stay the same or get worse over time. Even though it may be more of a "seep" now than a "leak", the cumulative effect of the fluid buildup on surrounding suspension pieces, over time, will cause a buildup of lube and the dirt you mentioned, unless you're willing to periodically get under the car to clean it.

I agree with Eric D, fix it, including the side cover o-ring. Once done properly, the fix is permanent. Find/use someone who is Corvette knowledgeable and not just a general mechanic. Have them follow the GM TSB on this to the letter. It works.

HTH

 

Thanks for the input thus far. I'm a fairly talented amateur mechanic but I'm not sure I want to tackle this repair. Is there a link to a write-up of what's involved in doing this fix correctly? Can a dealership be trusted to do this fix properly, or should I try to find a Corvette specialty shop to do it? Finally, can anyone recommend such a shop in the Houston area? Many thanks for your input!

 

Do a fluid level check and make sure it is not low so it does not gernade the rear.

Any leak is worth fixing when it comes to lubricating fluid and it is always a concern.

Best bet is to nip it in the "LEAKY BUTT"

Take care of it sooner rather than later or too late

Congrats on the new ride

Thanks,Matt

 

Anyone have the TSB for this?

 

Here you go:

http://forums.corvetteforum.com/c5-g...e-junkman.html

http://www.cajundude.com/outputshaftseal.htm

Its not that hard to do esp. if you have a good set of tools. I have replaced several cv joints (axle half shafts) in FWD cars and this is very similar. Expect an extra hour for cleaning up the underside of the car AND to double check everything.

I had a slight leak when I first purchased my used c5 back in '04 but within a 1500 miles or so it was leaking pretty bad. When I would drive it the gear lube would get on the hot exhaust pipe and burn. The stench and smoke was terrible so I replaced the seal the next weekend (after doing some research on the CF). It made a terrible mess and I wouldn't want to go threw that again. I would keep a close eye on it and as soon as you see drips on your floor (like the size of a quarter or perhaps smaller) its time to replace it.

I called the 3 local dealers around town and NONE of them gave me confidence in there ability to take care of the leak AND the car. All of them wanted the car over night and NON of them would put the car in the shop for the night and NON of them had secure parking outside. None of the service managers would take the responsibility of driving the car themselves (vs. letting some greasy mechanic or flunky drive it) so I decided to do it my self and i am glad i did. It really was not that bad of a job.

Good luck.

 

My 02 had 9,000 miles on it when I purchased it in October and it had the leak. I was able to do it myself with some help on my lift. They leak alot worse after long trips. Just make sure whoever fixes it has a proven track record of success with this repair. Too many stories of this repair having to be made over and over again (like the column lock fiascos). Good luck.

 

One other added note, buy the side cover o-ring from the dealer. It has been superceded with a slightly larger ring.

 

UPDATE - Tonight I checked the fluid level with the car resting on my garage floor - the diff was cold and the car hasn't been driven since last Sunday. No fluid emerged when I removed the fill plug, so I carefully inserted my finger in the hole and found the fluid level to be just slightly below the orifice (which I assume is correct?). Interesting observation: When I removed the plug the diff made a little "gasp" as if a little pressure was being released. Is this normal, or should I check the vent? Can anyone connect me with a diagram that shows where the vent is located, because I couldn't find it. Anyway, I raised the car and used a few cans of aerosol degreaser (my favorite polymer safe gun cleaner) to clean everything up so I can monitor this going forward. BTW, the right side is totally dry and clean.

Does my fluid level sound right? Can anyone help me find the vent and explain how to remove and/or clean it? Thanks for your help!

 

 

Wheelyneat,

No, you should not hear anything when removing the fill plug. The fluid should be right at the plug thread line with the vehicle level.

I can't find a photo to post, but it is located on the drivers side top of the differential. The vent looks like an inverted copper colored cap made out of metal. You can check the vent by using one of the hand type pressure/vacuum pumps equipped with a hose and small rubber cork that fits into the fill cap. You should NOT be able to pressurize the differential case. If the hand pump gauge shows pressure, the vent is plugged. It's not real common, but I have seen where mud or dirt collect around the vent enough to plug it.

 

no matter how you slice it you are losing fluid.

 

If it does hold any pressure, you could just keep pumping until the offending obstruction is popped loose.

The reason I rather doubt the vent-problem theory here is that he is only experienceing the seepage/leak at the left seal area. If too much pressure were the culprit, I think the right seal would/could fall victim too as it's no more special or different than the left.

 

I agree re: pressure causing both seals to seep, but I'll try checking the vent anyway. Since the fluid level is just below the filler hole I'll shoot a little LS lube in there to bring it up to the level of the threads. I walked through both of the above-referenced repair links and I'm curious - has anyone followed CajunDude's procedure and had success? He makes it seem like a fairly straightforward job. Thanks for everyone's input

 

There are a number of ways to perform this replacement. I tend to dismantle as little as possible to reduce the amount of time needed for the repair. Vehicle hoist is always a plus, but in a pinch for this seal replacement, just getting the backend of the Corvette off the ground high enough to allow a creeper and your belly to pass will work too. If the car’s suspension was lowered at some point in the past, you may also have to raise the front up some to allow enough angle to raise the backend high enough. Replacing the output shaft seal only can be done in about 30 to 40 minutes once the vehicle is off the ground. Replacing the output shaft seal and the left cover o-ring takes me about two hours. The hardest part for me is removal of the left cover stud that connects to the transmission. This stud has to come out to allow the cover to be removed and it requires heat sometimes to free it. I remove the left cover through the same opening that the output shaft normally occupies. It is a very tight fit and the side cover has to be rotated just right to pass through this opening. Even though it is a challenge, it can save a lot of time that would be used to get it out other areas.

I’ve worked on many different types of vehicles and I still believe the Corvette is among the easiest to work on. Can you do it in the same amount of time as I quoted above? Who knows, who cares, and if you are doing it for enjoyment of fixing your own stuff then it really doesn’t matter. Things that I believe are a must, get the right tools for the job including a good torque wrench. One of the most common newbie mistakes is to OVER torque fasteners.

On the theory as to why one side will leek more then another, the differential carrier (this is the part you see when looking at the differential) has the differential case (this is on the inside of the carrier and you can’t see) located on the right side. The differential case has a bearing on either side that keep the right output shaft (which is also shorter than the left) centered better compared to the left side that is cantilevered out from the for-aft centerline of the differential case and uses a bushing for a bearing unlike the right side. The bottom-line, it is a design issue more than anything else and part of why it is so common of an issue. Hey, just my personal opinion.

Regards,

Eric D