sothpaw2

Hi,

After I came back recently from a HPDE (hard use on the road course but not abuse), I noticed on my garage floor for the first time some oil. On inspection, the rear spring had oil on it under the diff but not past the axles on either side. The right side diff cover was clean and new looking; the left side had oil on it (plenty) and the shaft leading to it had some stain on it close to the diff.

So I gather the diff leaked from maybe the left side cover.

Question though: Since I did not fill it this time (shop did along w/other work but no work to the left side), could this be due to overfill? What happens if you overfill the diff and run it hard on a hot day?
(where does it leak from if overfilled??)

I have not seen any more oil on the floor due to easy daily driving. When I opened the fill plug it did not rush out but was close (get it on the finger...shop manual I think considers this full since car was level). I added 0.2L until it ran out just to be sure it was safe to drive around town.

For those that have had the classic leaky diff seals, is it a drip or a lot and under what condition did it leak more?

Just checking before I have it repaired; I would not want to fix what's not broken.

Thanks,

Andy

Last C5

Sounds familiar, it's probably the left axle seal. Just replaced mine for the second time on the track car. It's an easy fix with a lift and the part is only about $10. GM Part #88996703

Cybermind

From your description of the problem, it sounds like an overfill situation. Too much diff fluid will cause it to blow out the vent which is on the top of the diff casing on the driver side. This happens more when it is very hot outside or after very spirited driving. What you need to do is remove some fluid and bring the level down to about 1/4 inch from the fill hole. Make sure you are checking it on a level surface.

I had the same problem and it was indeed an overfilled diff.

lucky131969

Ok.......so it's overserviced again. Fluid level is supposed to be even, or just below the bottom of the fill hole.

sothpaw2

Indeed. But I don't have to leave it that way...just not sure what happened to begin with so wanted to add a little just in case.

So it's the axle seal specifically that goes on these cars...can someone provide a pic or description? What I'd like to do is try to see if it was the seal or if it came out the vent.

In that regard, where is the vent? Any pictures? Seems if I find oil at the vent then maybe I have my answer.

For sure this was not a few drops...this was enough to make a real mess and even get some on the back of the trans. I was really surprised when I put my finger in the fill hole and got oil on my finger (indicating as Lucky said, shop manual says this is full--car was level).

Thanks,

Andy

NatB

The rear differential leaks have to be watched- at least on my car.

After 4 years of ownership- I have seen a few drops come and go. Glad I haven't wasted time and money fixing. My best guess in my own case is overfill- combined with expansion of fluid due to the super hot summer we're having.

Unless you are seeing fluid covering your rear axle are and/or garage floor - just watch it and check the fluid level. Last time ( 3 months a go) that I saw any leak, I checked and the axle was full.

sothpaw2

Nat,

In my case I did indeed see fluid on the axle and on the floor. More than 1-2 drips on the floor--maybe 15-25 droplets. Signif. oil on the rear leaf in the center (straight part). If it was overfilled fine, if not, I should fix it. Can't be servicing it at the track and potentially leaking there.

NatB

FWIW- I had the same occur once about 3 months ago. Thought I had a problem, checked fluid level and it was fine. More than a few drops- infact the axle was grimy. Cleaned it all up and sprayed off with brake cleaner.

Not a drop since. Me thinks it was mayble overflll blow off thru the diff vent.

Last C5

It only takes a litlle oil to make a big mess. (voice of experience )
The last time I came off the track I had oil all over the springs, suspension, pumpkin, left half shaft, and even on the back of the car. When I checked the oil level I could still get oil on my finger when I put it in the hole. That time it was the axle seal.

It's actually fairly difficult to overfill these differentials by very much given that the fill hole regurgitates any extra you put in as you put it in.

With a cool diff you can change the axle seal without draining the oil. The proper full level is below the bottom of the seal until the diff gets hot and the oil expands. The vent is just to rear of the output shaft clear up on top the diff slightly to the drivers side. Good luck, leaks are a bear to find sometimes.

sothpaw2

Thanks! You had posted earlier that you have gone through 2 seals on your track car--were both left side axle seals? Most of my turns are right turns so the left would do most of the work.

What does the vent look like? Are we talking some slots or is it a small weep hole?

It seems as though if it were leaking due to over-filled and the vent is near the middle on top then I should have seen some oil on the back side and also on the right; basically all over. Agreed?

What I have is oil on the left side cover and on the leaf in the center portion. Even a little on the back of the trans. Nothing on the passenger side. Nothing on either suspension.

Last C5

See comments in bold below. . .

feeder82

take a look at this post, but read it all the way thru, you dont have to remove the cradle to change the seals
http://forums.corvetteforum.com/c5-g...-photos-2.html

Dennis Wilson

100% agree. The vent leak will run down the driver`s side exactly where the seal leak would. Only it will also be noticable above the axle as well. Had it happen to me.

Bill Curlee

Here are TWO more post that you can read to get a better handle on the rearend. While you have it out,, you can do some simple upgrades.

- C5, ragtopws6 , Upgrading your C5 rear with C6 Z06 guts, : http://forums.corvetteforum.com/c5-g...-z06-guts.html
-

- C5, Its_Go_Time, Output Shaft Install - Left and Right: http://forums.corvetteforum.com/c5-t...post1573407966

SteveDoten

good links Bill

the C6Z upgrade is easy, just need an arbor press

Bill Curlee

Yea,,, I had a friend make me a tool to fit over the cross shaft and used the press at work. Worked EXCELLENT!

Bill

jpulone

With 105,000 miles I had a leak with the car parked slightly up hill in my drive way.
I noticed a 1/2 in. hose on top of the diff. that was wet with oil that was not attached to anything and it was a rough cut. I didn't see any wet on the output shafts of the diff.
The car has never been service since new. I drove it again and parked it with the rear on the high side of my drive way and no leaks.
Any thoughts?

craig04c5

Mine leaves a spot or two if I drive it aggressively. If not no spots and it is not over filled. I check it annually. I would not spend the money unless you are sure it is actually a leak and not blowing out of the top tube. It has done this with my OEM 3:42's and later with my different differential 4:10's.

danny99

if it's an overfill, would fluid be spilled all over the left side? i have a situation now where fluid (clear, with greenish tint) is all over the driver side rear end. up top and on the rear fascia walls inside.. can't tell if its a leak from the differential seal, or from up top of the vent.

Bill Curlee

With the car LEVEL, drive train COLD, remove the fill. When you remove it, there should be a very slight in rush of air into the differential (vacuum)

If the vent is working correctly, it will let pressure out but should seal if there isn't any pressure. When it seal and the diff case cools, a small vacuum forms inside the case.

This vacuum helps the output shaft seals SEAL.

If the car is level and you remove the fill plug, any overfill will run out.

Bill