14 bolt leaking out of vent hose

[Rust-O-Matic]

I just finished swapping a '96 14 bolt full floater into my '66 C20.

Everything seems to work well, but during my test drive the vent tube leaked some oil out. And since there's no bed floor yet, the wind blew the oil all over the whole back half of the truck, so it's kinda hard to tell how much it lost. When I pulled the cover back off though, it appeared to still be pretty full. Anybody got any idea what would cause this?

My first thought would be that it's overfilled. When googling oil capacity, I get answers anywhere from 2.6 quarts to 5+ quarts. I filled my axle up to the fill plug, let the excess dribble out, then put the plug back in. It held right at 2.75 quarts. Is this too much?

I checked the temp of the diff. as well, to make sure there wasn't some kind of mechanical problem causing more heat expansion than it should. After about 15 mins on the highway at 65 mph, the pumpkin shows about 135 degrees.

[YoungPup1977]

Put a hose on it and extend the vent up into the frame with a vent in the end of the hose. See if that works.

[Rust-O-Matic]

I actually put a longer hose on already, and routed it up and further away. I then pulled the cover to make sure I hadn't lost very much oil, and refilled it back to the fill plug. It leaked out of the longer hose same as it did before.

After the first 10 miles or so, the leak seems to have slowed down or almost stopped. This is why I'm wondering if it was just a little overfilled. (?) I'm getting conflicting info on how much oil is even supposed to be in there though, so I'm not sure what to think.

[mongocanfly]

oil to the fill plug is where its supposed to be....how long a hose and how do you have it routed?

[jeffahart]

I hear this now and again and I'm beginning to think it's the pinion angle. What's the angle the way one sits on a 96 and what's the angle on your setup. I wonder if 2-4 degrees off spec is enough to let the gears start shoveling oil up that vent. A fix could be to put a canister on the end of the vent tube and let it bleed back into the diff when stopped. I run a 14 out of an 86 with no trouble.


j

[Wrenchbender Ret]

It could be the grease foaming. You might try a different brand of grease.
George

[Rust-O-Matic]

The vent hose is a little over 2 feet long, and routed straight up to the nearest crossmember, then 90 degrees over toward the passenger side upper shock mount.

Not sure what the pinion angle is. I used a 2x4 jig I made to match the pinion angle of the original Eaton when I put the perches on the 14 bolt.

[jeffahart]

Originally Posted by Rust-O-Matic

The vent hose is a little over 2 feet long, and routed straight up to the nearest crossmember, then 90 degrees over toward the passenger side upper shock mount.

Not sure what the pinion angle is. I used a 2x4 jig I made to match the pinion angle of the original Eaton when I put the perches on the 14 bolt.

And I am a fan of dialing in the angle with new perches. But, I've heard of this condition a few times and wonder what causes the perfect storm of getting oil up that little vent hose. I'm just wondering if with the pressure, the gears spitting oil and maybe the angle being just right there is an effect where; the pressure along with the driven oil( spitting from the gears) and exact right angle allow some oil to be forced up that hose. What else could it be? Or all of the 14 bolts would leak, but you only hear of it very rarely. What would be an interesting test would be to stick in a 3 degree shim for a few miles and see if it stops.


Good luck. Keep us posted!


j

[95 S_Trucker]

What brand gear oil did you use? Lucas is known to foam.

[YoungPup1977]

We have a foaming of the gear oil issue ?

[Rust-O-Matic]

Its full of Volvo Penta full synthetic 75w-90. It's marketed for marine use, but is just standard GL5 gear oil, and I've got a bunch of it.

There wasn't any noticeable foaming visible when I popped the cover off the other night (right after I drove it) to investigate. Just fresh, clean oil.

The pinion angle is a possibility, but I feel like this might be a more common problem if that were the case. I can't seem to find too many others online with the same problem. The ring gear is on the opposite side of the housing from the vent, so I'm kinda skeptical but I suppose anything is possible.

The odd part is that the leak seems to have drastically slowed down after the first bit that blew all over the place. Almost as if it was overfilled, though I'm fairly confident it wasn't. This assumes there isn't a specific fill procedure I'm not aware of. I just filled it to the bottom of the plug hole, let it dribble out, and put the plug back in.