Rearend Vent Leaking

[matthon]

Searched, found same issue, but solutions don't seam to apply.

Upgraded to bbp axles, housing completely cleaned, center section sealed up with new gasket, vent cleaned up inside and out and resealed, used a little green tube gear oil rtv on both.

Rear was filled on a lift just below the fill hole.

Swapping shocks this week, noticed it's been leaking enough to cover the housing and sway bar, but not enough to drip.

Everything is sealed up, no leaks, except the top of the vent.

I see some put a hose on it and route it up to the shock mounts.

I don't really want to do that as I have other cars that don't have this issue, trying to figure out what's up?

 

[Desoto291hemi]

What kind of gear oil did you use ?
How did you clean the vent ?

Tommy

 

[matthon]

I used the additive and either Valvoline 75W-90 or 80W-90.
Took vent out, popped off top, cleaned in parts washer, it was clogged iirc.

 

[dadsbee]

Axle gets hot and they mist, why it's a vent.

 

[matthon]

They're designed to vent fluid?

I have 2 other cars with 8.75 rearends, one completely rebuilt, the other new axles and seals, one is a bb 4 speed same as this one, drive them all the time, no venting of fluid.

 

[dadsbee]

They all mist a film of oil... unless they're clogged!

 

[matthon]

I kid you not, the other 2 are not clogged, both filled correctly, I'm looking at them right now.

 

[67Dart273]

How bout ratio? I would bet lower gears create more heat, suds, slop, mist, etc than high speed gear

 

[matthon]

Don't know.
Car leaking is a 383 4 speed with 3.23.
Others are 383 4 speed with 3.55, and a 318 auto with 2.97, all are Sure-Grip.

I have driven all 3 daily around town, as well as long trips, 3-5 hours at a time.

Recently took the 3.55 car out for a few hours on the highway, and even after years of use the only sign of fluid is a saturated vent gasket.
Rubbed it with my finger, nothing there but a stain of fluid, nothing past what is in the pic.
I know I did a number of fastener checks soon after finishing this car, as I replaced everything, so it might just be from it being loose initially.
No oil on the vent itself.

 

[Oldmanmopar]

That is a 69 or earlier housing. They had issues with them leaking that is why the vent was moved to the axle tube on 70 and later. The fix is extend the tube into the housing farther . This stops the lube from travelling up the tube when flowing down the hill on the housing. You'll always relieve pressure from the housing due to heat. Your tube is scavenging oil and being pushed out.

 

[AJ/FormS]

I see some put a hose on it and route it up to the shock mounts.

I don't really want to do that as I have other cars that don't have this issue, trying to figure out what's up?

Not a valid reason, IMHO.
It's fast, It's easy, it's cheap, and It works.

 

[matthon]

The fix is extend the tube into the housing farther

Interesting. Not sure how exactly to accomplish but I like it, and your reasoning sounds accurate.
The car leaking is an a-body, the others b-body, maybe the a-body vent is a little higher on the housing.
I'll have to measure.

Not a valid reason, IMHO.
It's fast, It's easy, it's cheap, and It works.

I understand your opinion, however my brain wants to know the why before I fix or change something.

Also read another thread where that did not work, although some thought it would eliminate water getting in the housing if submerged, but if that's a concern there are bigger problems.

 

[67Dart273]

Lots of rigs have hose vents, particularly pickups and 4wd

 

[Professor Fate]

Oldmanmopar nailed it.
'69 and earlier housings had the vent up at the center section- it allowed oil mist to escape through the vent.

In '70 they moved it a couple inches farther down the axle tube, away from the gears in order to eliminate the issue.

As a side note, this is also why brake line suppliers differentiate between '69 and older, and '70 and newer 8.75s- the vent, and therefore the brake tee, is positioned differently and the lines are different lengths. So when you order lines, make sure you order for the year of the rear, not the year of the car if it's had a rear end swap.

 

[Bewy]

Er...overfilled?

 

[CFD244]

Any chance that it's weeping past the threads and not the vent hole?

 

[Desoto291hemi]

I don’t really think so .

OldmanMopar , and Professor Fate have it I believe .
There is just so much oil churned up by the ring gear spinning that it creates quite a mist ,,and excessive pressure .
Mopar figured that out as well , back in the day .

I knew it but forgot to check on the years ,,,,boy,,,I feel stupid .

Tommy

 

[jos51700]

I just wanna say, dang, the knowledge and memories of you guys, to know that's how and why there's a difference in those axles.

So, if that's one that's prone to weeping, could a guy weld a little baffle on the inside of the housing to limit the weep through the vent, or would people with those axles just be better to loop a hose up n over?

 

[TrailBeast]

Not a valid reason, IMHO.
It's fast, It's easy, it's cheap, and It works.

And if you stuff a little scotch bright in the end it won’t suck dust back in when it cools down.
Oil mist on the scotch bright catches it.

 

[AJ/FormS]

And if you stuff a little scotch bright in the end it won’t suck dust back in when it cools down.
Oil mist on the scotch bright catches it.

As for me; I ran the oil line up and back down a few inches, so that, theoretically, the dirt/dust/water is not supposed to go uphill.
I like your idea better; I wish I wouldda thought of it. lol.

 

[AJ/FormS]

I just wanna say, dang, the knowledge and memories of you guys, to know that's how and why there's a difference in those axles.

So, if that's one that's prone to weeping, could a guy weld a little baffle on the inside of the housing to limit the weep through the vent, or would people with those axles just be better to loop a hose up n over?

That should work, if the oil coming outta there was being flung there; but you gotta take the pig out, and the clean the oily oily housing. Seems like a lotta work, when the hose-trick is cheap/easy/fast, and it works....... lol.
However, that oil coming up outta there is not liquid, nor is it being flung up there, at least not most of it. That oil is coming out of there because the air inside the beast expands as the guts get warmer, and the expanding air, carries the fog with it. Then, when the thing cools, it pulls atmospheric air back inside.
So, you could say, the rear end is just breathing. Your weldment is not gonna stop that.
Whereas the standpipe-hose traps the oil-fog which continuously condenses and runs back in. I've never seen the top of that hose wet.

I've seen GM 4x4 pick-ups run the same hose up from the front diff and IIRC, over 2ft long ending close to the master cylinder. It seems, even the factory uses this method.

 

[matthon]

My 4x4 has the hoses as well, my understanding is they are more for keeping water out when you're wheeling, yee haw!

 

[jbc426]

Searched, found same issue, but solutions don't seam to apply.

Upgraded to bbp axles, housing completely cleaned, center section sealed up with new gasket, vent cleaned up inside and out and resealed, used a little green tube gear oil rtv on both.

Rear was filled on a lift just below the fill hole.

Swapping shocks this week, noticed it's been leaking enough to cover the housing and sway bar, but not enough to drip.

Everything is sealed up, no leaks, except the top of the vent.

I see some put a hose on it and route it up to the shock mounts.

I don't really want to do that as I have other cars that don't have this issue, trying to figure out what's up?

View attachment 1716437378

View attachment 1716437379

I went through this with mine, which had the vent farther out on the axle tube.

I removed the metal cap and silver soldered a small, short metal tube inside the opening, so I could attach a short 2 foot length of hose with a bit of scotch bright pad stuffed into it. The hose looped up and pointed downward much like the vent tubes on 4WD vehicles.

That ended the seepage, mist or whatever that always kept that area wet with gear oil seepage.

 

[70dart340]

On my 4X4, I put a small sintered bronze filter on it.