Front differential vent fitting

[east302]

So I spotted what looked like a left axle seal leak on this 98 K1500 that we bought for my son. I should’ve just not looked under it.

Got the axle off and now have two questions:

1. The flange hits the frame...will removing the two driver side differential bolts and loosening the two on the right side let it lower enough to clear?

This thing is so damn dirty.

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2. The vent hose on the front differential was actually not connected at all. Mud was holding it in place. The vent cap that threads into the differential literally pulled right out and then broke when I tried to clean it. It doesn’t fit at all, it’s too small to thread into place. It has part number 26015414 on it, but part number 12479490 pulls up when I look for a new one.

Has anyone used that 12479490? One of the Amazon reviews said it didn’t fit his 98 K1500 so...

Just don’t want it buy another bum part. Know what I mean?

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[mtl111]

I took a pic of my 1999 GM Service Manual for GMT400's not the new Silverado. Notice number 2, its says remove carrier assembly from vehicle. I got on a creeper and looked at my front diff, and yes mine would barely touch the frame too....which totally sucks!
As for the vent, I looked it up on Wholesale GM Parts and came up with GM 12479390 which is the part you have in the Amazon listing. If you don't want to take a chance, wait til Monday and call your local dealer.

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[MIHELA]

The white vent cap is the new design, it was designed to prevent fluid siphoning out the hose with 75W90.

 

[454cid]

The white vent cap is the new design, it was designed to prevent fluid siphoning out the hose with 75W90.

How would fluid siphon out the hose? It's supposed to be mounted to the shroud.

 

[MIHELA]

How would fluid siphon out the hose? It's supposed to be mounted to the shroud.

I bet GM wondered that too, but it is a thing. There was a service bulletin.

 

[454cid]

I bet GM wondered that too, but it is a thing. There was a service bulletin.

Do you have a link? Google isn't finding it for me.

 

[MIHELA]

The TSB is 03-04-19-001A. I don't work at a GM dealer anymore so it's hard to find these. I guess the issue is a seal incompatibility. The TSB mentions that 9.25 diffs and extreme cold with 80W90 can cause failure due to lack of lubrication. 2004+ vehicles all came with the white vent and 75W90 from the factory.

 

[east302]

The TSB is 03-04-19-001A. I don't work at a GM dealer anymore so it's hard to find these. I guess the issue is a seal incompatibility. The TSB mentions that 9.25 diffs and extreme cold with 80W90 can cause failure due to lack of lubrication. 2004+ vehicles all came with the white vent and 75W90 from the factory.

Do you remember if the white vents were a direct replacement for the black ones on the 8.25?

Thing is, the black one that I “removed” was too small to thread in - it was just sitting in there, making me wonder if the white one would fit or what this differential even came out of.

 

[MIHELA]

They are the same size. It's a straight part number change.

 

[454cid]

The TSB is 03-04-19-001A. I don't work at a GM dealer anymore so it's hard to find these. I guess the issue is a seal incompatibility. The TSB mentions that 9.25 diffs and extreme cold with 80W90 can cause failure due to lack of lubrication. 2004+ vehicles all came with the white vent and 75W90 from the factory.

Thanks for posting the number.

That's a seal compatibility issue with synthetic. It has nothing to do with siphoning gear lube out the vent, from what I'm seeing online.

Edit: It's also a 2002-2004 GMT-800 thing, which kinda surprises me, since I thought GM switched all axles to synthetic in 99, but apparently that was only rear axles.