front axle vent

   / front axle vent #1  


Super Member
Nov 25, 2016
Santa Cruz Mountains CA, Southern OR
Branson 3725H Deere 5105
My Branson has it's front axle vent on the right steering knuckle. If you work or park on a slope to the right, it leaks oil out the vent. The dealer sent me a fix they had made up which is a ~2" extension. It helps but it's still not enough for me. Land is too sloped here. So I am thinking of making a better one.

My design would use a hydraulic live swivel connected to the old vent fitting on the axle, and clear vinyl hose running to the center of the tractor in front of the radiator where I will locate a small tank, probably made from PVC. The idea is that when pressure builds in the axle, it will force any oil in the tube up to the tank where air can bubble out past it. As the axle cools, it will pull back the oil in the tank and line. The line may dip down as it runs across the axle so there will be some oil that sits there. My main concern is that the ~2ft head to the tank. The pressure in the axle has to be great enough to push the oil up to the tank. My calculations using head of water (even though it weighs more) is that it'll be about .03 psi. There's also viscosity of the 80w-90 to consider but I don't know how to factor that in. The psi sounds low but I have no clue what it takes to push seals out.

I was thinking of using 1/4 hose to minimize the head pressure and make for easier routing but the viscosity may make it harder to push the oil through it.

Any suggestions? I know the tubing won't be sturdy, once I'm satisfied it works and no longer want to observe the oil I can replace it with something sturdier.
   / front axle vent #2  
Have you tried sourcing the newer vent style they are using now?

Can't find any pictures at the moment though.
   / front axle vent
  • Thread Starter
I was assuming the axle is different for that... at least a hole tapped in it somewhere. If it's a bolt on, that would be great.

I asked my dealer what the threads are on the fitting and told them I was going to make something. If there was a known retrofit I'd hope they'd have told me.
   / front axle vent #4  
It replaces the orange cap/fill plug, so it should fit your tractor and mine for that matter.

Mine also leaked on hills, but it came a bit overfilled from the dealer. Once it leaked to back the right level, it stopped.
   / front axle vent #5  
sounds like maybe too much gear oil? I cant imagine the angle my Kioti would have to be on to leak .
The axle just has to have enough to service the outer gears.
   / front axle vent
  • Thread Starter
It's because the vent is on the far end of the axle. If the tractor's on a tilt and the vent's on the downhill side, all the oil in the tube ends up on that side along with some from the wheel gears and diff. I've got it at the factory level on the dip stick. I think it's high enough so there's oil in the tube for the diff gears and shaft bearings.

I'll have to look for the new factory vent now. It's too bad that the big red's on line parts lookup is gone and Branson US's one is not up yet.
   / front axle vent #7  
and is that the fill point as well? or just a vent?
   / front axle vent
  • Thread Starter
You can fill from either side. One side has a plug with the dipstick, one has a plug with the vent. They're on what Branson calls the "knuckle" which is the part that turns to steer, and passes the drive to the wheel gear.