ZeeOSix

Just below the vent located near the top left hand side of the differential, there are what looks like two machined holes that have black steel plugs in them (Note - use a mirror and flashlight to see them with diff on the car). Anyone know what those holes are/were for and why they are plugged?

I've noticed some oil residue in this area, and I can't tell if it's from the vent or possibly from these plugged holes. I guess it's possible that these plugs seep some oil when the differential gets hot and the aluminum expands more than the steel if the steel plugs aren't real tight to start with. Also, with some miles it's possible that the steel pugs could slowly loosen up with repeated heat cycles.

Maybe this is an unknown source of differential fluid leaks that some owners experience. I've heard of some owners having repeated leakage problems even after their car has supposedly been fixed by the dealer for the axle seal and/or diff side cover leaks.

If these plugs leak differential fluid an easy fix would be to cover them with an oil resistant, high temp RTV after cleaning them up well with a non-residue cleaner.

Anyone got a differential out of their car ... and if so maybe you could take a couple pixs of the vent area where these plugged holes are so people can see what I'm talking about.

ZeeOSix

Anyone have a differential sitting out of the car?

If so, could you take a few pixs of the vent area and the holes with the steel plugs located in the area below the vent towards ther rear of the diff?

Where's all the diff experts ??

happa

I just pulled my tranny out tonight, I just took some pics of it, should be up tomorrow

Bill Curlee

When CONNECTICUT and I were at the Forum Cruise in this spring, we spoke to Phil from DTE and he stated that the vent on the C5 and C6 rear end is constructed so that it allows air to escape but should not allow air to re-enter the rear end. This design will allow the diff to run under a slight vacuum. If you let the diff cool down, remove the "FILL PLUG" and you should hear a slight in-rush of air when the fill plug comes out Of the cover. The vacuum helps the seals keep the oil in the diff. See if yours is maintaining that slight vacuum.

BC

ZeeOSix

Yeah, I've noticed that the cap on the diff vent seems to have some kind of spring action to it. Apparently, the vent must be some kind of spring loaded "valve" to vent air when pressure builds up inside the diff.

So if the vent "valve" was not sealing, I wonder if oil would vent much easier? The oil I see on my diff sure seems to be coming from the vent, or maybe from these two plugged holes in the diff case near the vent.

happa -- Cool ... yes, please post pixs of the diff vent area. Thanks.

Bill Curlee

Im at Carlisle right now and I will take pictures of some while Im here.

BC

ZeeOSix

... will be interesting to see if pixs show any signs of oil leakage from these two plugged holes and also the vent.

happa

Heres some I got. Hope it helps! Hope its what your looking for.

ZeeOSix

Yes ... those are good pixs -- thanks! . Looks like someone might have cleaned off the plugged holes so they show up good in the pixs. Also looks like there is kind of oil residue build-up near these plugged holes over time ... obviously this differential has some long term build up on it. But if you look at the two plugged holes, it seems it's darker around them. Looks like more oil residue build up near the two holes then there is around the vent itself.

My theory is that maybe some differentials might leak from these holes if the metal plugs in them aren't sealed very tight. Any oil that come out of them can run down the left side cover edge and drip off the bottom cover bolt.

ZeeOSix

Great ... I'd like to see if other differentials show the same residue buildup near these 2 plugged holes.

Mike Mercury

the air vent is directly upwards from there. And the vent is a source for fluid expulsion. The "plugged" location may simply be a recessed area for the vent ejected fluid to "pool" at - and it could count for the dis-colorization.


Just a guess.

timemender

Sounds very logical.

ZeeOSix

Seems to me that if all the dark area residue was from the vent then you'd also see dark area from the vent down to the plugged hole location. It looks pretty stain free right next to the vent as opposed to the area below where the plugged holes are.

So, I came up with a little experiment to determine if oil is collecting in this area. I devised a "Diff Diaper" made from oil absorbent material (used for hydraulic leaks) and packed it in tightly, and attached it over the two plugged holes with aluminum tape after cleaning this area so there was zero residue. See photo below.

Idea here is to see if the drops stop appearing on the left side cover's lower bolt, and to see if the diaper becomes wet with any diff fluid after some driving. It's pretty easy to get your hand up in this area without even jacking up the car if you lay on your back and reach up just right. I left the area near the vent open, and it's pretty easy to reach up and feel just below the vent to see if any fluid has puked out of it. It was difficult to get a good photo since it is kind of tight up there -- photo has been rotated and chopped for easier viewing and sense of orientation. Compare to the pixs of the differential above to get your bearings. You can see the top of the vent (gold color) near the top of the photo.