- 991
- 1,860
- 93
- Location
- Wauchula, FL
Filling my new eco hubs with gear oil I noticed it was pressurizing. Lead me to check for proper ventilation. While trying to find where it vents to is a lot more complicated than it should be. After figuring it all out I figured I should share this information for everyone. 
A quick drawing explaining how it’s plumbed. Stewart and Stevenson made some bad choices on this if you ask me. I can understand using a large hose for coming off the hubs but then the drivers side is choked down to a 1/4” line, makes no sense.
Here is the culprit on the top of the axle closest to the passenger side.
The disconnected hose is where the clog was it goes up behind the cab to the vent.
This is the vent.
A 1/4” drill bit cleared the clogged area.
The largest coming from the front hubs is the vent line and the goes to the frame.
I’m guessing this is what caused my front axle seals to fail. Or maybe they didn’t fail completely and the case was pressurizing forcing oil out. Either way I’ll sleep better knowing I have all new seals and I’ve cleared the clogged vent.
Hope this helps understanding the mystery of how the front axle and hubs are vented.
A quick drawing explaining how it’s plumbed. Stewart and Stevenson made some bad choices on this if you ask me. I can understand using a large hose for coming off the hubs but then the drivers side is choked down to a 1/4” line, makes no sense.
Here is the culprit on the top of the axle closest to the passenger side.
The disconnected hose is where the clog was it goes up behind the cab to the vent.
This is the vent.
A 1/4” drill bit cleared the clogged area.
The largest coming from the front hubs is the vent line and the goes to the frame.
I’m guessing this is what caused my front axle seals to fail. Or maybe they didn’t fail completely and the case was pressurizing forcing oil out. Either way I’ll sleep better knowing I have all new seals and I’ve cleared the clogged vent.
Hope this helps understanding the mystery of how the front axle and hubs are vented.