Strategies for a front diff leak

[6716]

So, the front diff leaks, I think it has for all the 15 years I've had it. It's been dry a couple of times, I'm sure.

I don't think it is the outboard axle seal, I replaced it with the GM seal, still leaks. From the oil/dust pattern on it, it sort of looks like it is coming from the drain bolt. I'm thinking of thread tape there. I've seen the drips on the ground, I've seen them hanging on the bottom of the diff, but I haven't really seen it running down the side or anything.

I've also read maybe the vent tube is blocked, and the pressure inside the diff forces it out, so I am planning on checking the tube and the vent bit coming up from the diff.

I've also read on the old site people slather RTV where the case halves come together. I'm planning on that as well.

Fill plug is stuck, won't come out. Last time I filled through the axle hole after replacing the seal. This time I will fill through the vent.

Am I missing anything else obvious? If this doesn't fix it, I think I'll just have to try to keep up with it, I don't think I'm pulling that diff down for the other side seal.

 

[Mooseman]

What about the inner seal?

For the fill plug, try using some heat and a twist type bolt remover. A new one may still be available. It's the same plug on full size trucks. You can keep trying, can't make it any worse. Maybe an air hammer might work to loosen it up.

For the drain plug, maybe just replace the gasket. Teflon tape won't hurt.

I know the 02's had problems of leakage between the two halves and modified the mounting bolts. Not so much for later years.

I would clean the area thoroughly with brake cleaner, put some UV dye and fill it with oil to try and find the leak. Using a UV light, it should make it pretty evident where it's leaking.

 

[flyboy2610]

For the fill plug first try tightening it ever so slightly, and then try to loosen it. Go back and forth with it, it may help.

 

[Mektek]

I have a leak at the inner shaft seal. From what I see the differential has to be removed to change that one - a huge undertaking. The leak is small enough that I put a sheet of foam beneath and that absorbs the drip. Every year or two I can top up the differential.

I wonder if it would be less work to remove the inner shaft and pull the seal. then unbolt the diff and push it to the side - let the old seal fall out and carefully insert the new seal. bolt the diff back and tap the new seal in place from the inside..

Has anybody tried this?

 

[6716]

@Mooseman the inner seal seems like a lot of work, so I hope that's not it . I think I might replace the gasket and teflon the threads. The UV dye is new trick to me, so I will check it out.

@flyboy2610 that thing is as good as welded tight. Won't budge a bit either direction.

@Mektek

that guy seems to think you can do what you described.

Thanks

 

[Mooseman]

You basically have to pull both axles, the disconnect, the intermediate shaft then unbolt the diff from the pan. You won't be able to pull it out completely so might have to replace it with it dangling down from the frame. Somebody here did that.

 

[Reprise]

I just pulled my diff a couple of weeks ago, but haven't split the case yet. Right now, I'm in the middle of rust remediation on the Accord, and discovered today that I need to replace the 'wiper pulse board' on my Sierra. But I'll eventually get to the diff.

The problem with mine is that it leaks, as well. From what I read, the GM front diffs (ours, full-size trucks, etc.) have a common problem with leakage.

Like yours, I think mine was leaking for a long, LONG time.

If you're not in a rush, I'll take some pics with the case split; that'll allow us to examine the inner seals (I'll replace mine in any case, but I'd be fine with testing first, to see if the case was leaking by simply RTV'ing it / refilling it / suspending it someplace where it can be evaluated (I'm nowhere near needing to re-install it in my Envoy, so have no plans to put it back in the truck soon).

It will probably be at least a week until I can get to this, based on the two jobs in front of me. My village is currently replacing my street curbs and resurfacing my street afterward (so I can't swap vehicles in / out of the garage for about a week. That's how I figured out the Sierra's pulse board went south today -- by driving it in the rain... LOL)

 

[coolasice]

when my 08 had a constant drip from the diff it was from the case halves, I had to take the diff out and split it to re-seal the cases. haven't leaked a drop since. (I did replace all the axle/yoke seals at the same time)

 

[coolasice]

You basically have to pull both axles, the disconnect, the intermediate shaft then unbolt the diff from the pan. You wonèt be able to pull it out completely so might have to replace it with it dangling down from the frame. Somebody here did that.

You can pull it out the top... That's how I did mine, remove radiator fan/shroud, altenator, battery+tray, and move ac compressor out of the way... it fits right up that area. Great time to replace thermostat too. To pull the diff you need to remove the 4x4 disconnect.... if you never took it off before, plan on getting a new one as they usually break when trying to remove. turned my 2 day job into a week long one.

 

[flyboy2610]

The big issue with the front axle disconnect is that it "corrosion bonds" with the oil pan. To remove it, remove the bolts and then use a hammer to tap the side of the disconnect down towards the ground for a 1/4-1/2" or so. Then tap it upwards towards the hood for about the same amount. Now the corrosion bond is broken.
Gently tap and pull the disconnect out of the oil pan for a small amount, then push it back in. Repeat the process, going a bit further each time, until the disconnect comes out of the pan. It's like fine china or crystal: if you're not gentle, you're going to say "Oops."
Trying to pry it straight out is almost guaranteed to break it.
And make sure you use anti-seize when you replace it.

 

[coolasice]

The big issue with the front axle disconnect is that it "corrosion bonds" with the oil pan. To remove it, remove the bolts and then use a hammer to tap the side of the disconnect down towards the ground for a 1/4-1/2" or so. Then tap it upwards towards the hood for about the same amount. Now the corrosion bond is broken.
Gently tap and pull the disconnect out of the oil pan for a small amount, then push it back in. Repeat the process, going a bit further each time, until the disconnect comes out of the pan. It's like fine china or crystal: if you're not gentle, you're going to say "Oops."
Trying to pry it straight out is almost guaranteed to break it.
And make sure you use anti-seize when you replace it.

I did exactly that... the corrosion was so bad I had to drill/chisel out the remains from the pan after it cracked and broke off... it's almost a certain thing if it has never been changed before

 

[Mektek]

Woohoo! I'm glad my idea for replacing the inner seal is possible! It's still a helluva lot of work, but definitely less than removing the whole differential since no other problem exists.
Next order from the rock will have one,

 

[6716]

So, lil' pro tip here to start us out, if you are going to add the UV dye to the diff oil it is probably best if you don't spill it all over everything in that half of the engine compartment. Just sayin'.

I cleaned up the diff with brake cleaner, drained it and got significantly less than a quart out, but I got some to come out, so that is good I suppose. There was a washer in there between the drain plug and the case, a hard nylon washer.

I added some oil through the vent tube with the plug out, just to confirm there wasn't a blockage there, although the cap on the tube (I had to cut the tube to remove the cap) ... I'm not sure there's much room for breathing on that thing. It's not like the cap on the rear diff that seems to have a way to pop up and down if there's pressure. Anyway it was clear from the tube to the diff. Taking the PCM off helped find the tube.

I put in about .25 of an ounce of dye to the one quart of fluid.

Before I filled I just got the drain plug finger tight with the new washer in there, it was a Felpro, and it was a rubbery sort of washer, flexible, with a ridge on the outside of it. https://shop.advanceautoparts.com/p/felpro/20680588-P Different, anyway, than the hard nylon washer that came off.

When I tightened the drain plug though, it kind of squished out of there a little. So I backed it off until it didn't do that, but that seemed not tight enough (I suppose torque specs would tell me for sure) so I tightened it some more and it kind of squished again but it still doesn't seem tight enough but if I tighten it down more the washer will just squish out more.

I guess I kind of expect it to leak, so I will see what the dye tells me.

 

[6716]

The dye leads to the outboard axle seal. And it leaks something fierce. Might also be the drain plug, but the seal leak flows over the drain plug and down from there, so I can't tell for sure.

I replaced the seal maybe 18 months ago, along with the half shaft. So, I don't know what more I could have done there. Other than do what I did this time, I suppose, but I didn't know the dye trick.

It occurs to me now that it could either be leaking on the outside of the seal, or the inside of the seal. I wonder if I will be able to tell when I get the axle out, of course the tripot is in the way now. And when the axle comes out, it might drip some oil/dye on the inside where it might not have been before, and make it hard to tell. Well, maybe if it is on the outside, I will be able to see dye on the case and the seal once the seal is out.

If it is on the outside of the seal, I wonder if I should just RTV it. I kinda want to RTV it either way. If it is leaking on the inside where the seal meets the axle, I don't know what can be done other than hope another seal works this time?

I think I might get the seal started in the case, then run a bead of RTV around it, then press it all the way in. Most of the RTV will get scraped off by the diff case, and maybe I'll just smooth it out over the part where they come together. Maybe run another bead over the top of it. There should be room between the back of the tripot and where a bead of RTV would sit on the case at the seal junction.

It's got to be problem with the case opening, right?

 

[gmcman]

Sorry for the late reply, you can replace the inner seal without removing the diff.

Just rotate it in the frame and access from the bottom.

I can add more to this later..... Tied up at the moment

 

[6716]

Sorry for the late reply, you can replace the inner seal without removing the diff.

Just rotate it in the frame and access from the bottom.

I can add more to this later..... Tied up at the moment

No worries. It's actually the outboard seal. I was wondering if it was leaking on the outside of the seal between the seal and the case, or on the inside of the seal between the seal and the axle.

 

[Mooseman]

At least it's not the inner seal. Who knows what happened to the new seal. Maybe it got deformed while being installed or nicked by the axle.

 

[TollKeeper]

Sorry for the late reply, you can replace the inner seal without removing the diff.

Just rotate it in the frame and access from the bottom.

I can add more to this later..... Tied up at the moment

I can confirm this is true on the I6 engines.. Cant do it on the V8.

 

[6716]

Replaced the seal today, and I added some diff fluid resistant RTV around the outside after I had just tapped it in a little, and then tapped it the rest of the way in. The seal isn't flush with the case, it sticks out a hair. Not sure how well I did that, or if I did myself any favors there or just made it harder to take out next time. The RTV has a 24-hour cure time so I will drive it tomorrow and see if it still leaks. I made sure to get this seal from a dealership, to rule out any issues with non-OEM.

I couldn't really tell if the old seal was really messed up bad, or it just messed it up real bad taking it out. Possibly both. But I was super careful putting the axle back in.

I also RTV'd the drain plug, and got rid of the rubber Felpro washer. I went back to the original hard nylon washer, and did RTV on both sides of it. Especially since the fill plug is stuck, filling is a pain through the tube, so I am hoping this knocks out the leaks all together. I feel like the excessively fast fluid loss rate this last time around when I first added the dye was partially due to the Felpro washer, but I don't know that, either. Also added dye again this time.

I guess time will tell.