Differential Fluid on Underside of Blazer

[trukman1]

Just installed a new muffler/ tailpipe and noticed the entire rear of the under body is covered in oil (grease) that appears to becoming from the hose vent from the differential.

Haven't pulled the differential cover yet but I've been driving trucks for a long time and never seen this before.

Any suggestions for what I need to look for before I start tearing into things? What could cause it?

Thanks!

 

[Frankenchevy]

If it’s only coming from the vent, maybe someone managed to overfill it. Odd that fluid could consistently come out the vent, though. If the condition and mileage of the diff oil are unknown, now wouldn’t be a bad time to pull the cover, swap the oil and put in a new gasket.

 

[trukman1]

If it’s only coming from the vent, maybe someone managed to overfill it. Odd that fluid could consistently come out the vent, though. If the condition and mileage of the diff oil are unknown, now wouldn’t be a bad time to pull the cover, swap the oil and put in a new gasket.

Blazer has 72,000 original miles. Overall very solid, rust free vehicle with only cosmetic problems from PO who had "head in butt" syndrome. I can't say he didn't (or couldn't) figure out a way to screw this up to but I'm at a loss how it can happen.

Basically, I'm not sure HOW the differential can be overfilled. I used to drain the fluids and after replacing the cover, fill with fluids until the fluid came out the fill hole. Can extra fluid even be put in? If so, why would someone do that? If not, is there a differential problem that can cause this condition? I'm going to pull the cover but I'm just confused what could cause this condition.

Thanks for the response!

 

[Frankenchevy]

I'm not sure HOW the differential can be overfilled

It would be really hard...like filling the diff fluid with the truck on a steep driveway with the fill plug pointing up.

 

[trukman1]

Just returned from parts store with gasket and fluid. Will let you all know what I find when I open it up. Hopefully tomorrow. Just perplexed how it blows 80-90W fluid out. That's pretty thick stuff!

 

[PrairieDrifter]

No pinion seal leak?? What about your axle seals?

 

[shanegtr]

possible what ever oil was in there had a really bad foaming issue

 

[Backfoot100]

Or the rear end somehow went underwater and filled up. Heard of it happening before but never actually seen it.

 

[DanMcG]

does your vent hose run all the way up to the underside of the bed?

 

[Snoots]

Don't forget the posi additive (if you have one).

PO could have had a 'roar' from the rear axle and tried to cover it up by cramming more oil in the pumpkin.
While you have the cover off you may want to 'ink' the gears and check for runout before replacing the cover.

 

[yevgenievich]

Here is one that did it.

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Or the rear end somehow went underwater and filled up. Heard of it happening before but never actually seen it.

 

[Big Chip]

Here is one that did it.

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That’s ugly.

 

[Backfoot100]

Here is one that did it.

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OMFG that's really nasty.

 

[Dougnsalem]

Or the rear end somehow went underwater and filled up. Heard of it happening before but never actually seen it.

And here's mine I did last summer. The PO raced a hydro. I don't think they ever changed the fluid.

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[Dougnsalem]

That’s ugly.

Nah bro.... Yo Momma ez ugly.