Axle Vents

By Bill Cooke

This seems like a no-brainer, right? Well it is, but so many people don't check this before they take their trucks swimming. I know I didn't and when I checked the diff fluid I found what appeared to be a chocolate milkshake lubing my rear gears. Not Good! The stupid factory vent was letting way too much junk in the axle.

You see, the warm air in an axle expands as you drive. Without a vent it would have to find another way out, usually into your brake linings. As soon as you hit cold water a vacuum is created by the rapidly cooling air inside. If your vent is below the water level, bingo! water in your gear oil! Not good. The solution is easy, move the vent above the water level. Follow along and I'll show you how I did this on my '79 Dodge W150.

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The stock 8 3/8" rear axle in my Dodge is a little wimpy in a many ways, the vent was the most urgent. As you can see the vent just runs under a cover on the axle tube. This is only about 18" off the ground and I have been know to hit 30" of water easy. On an axle with the little stubby caps you will have to remove it and replace it with a fitting that let you hook up at least a 5/16" hose.

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I was able to just remove the cover and gently bend my vent tube up to meet the new hose. To insure a good seal, I put a double flare on the steel tube before slipping the new 5/16" fuel line over it. Use hose clamps! If you want to get really trick, use that accordion hose for air compressors. It comes in bright colors and all the women love it!

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I simply used plain old fuel line and ran it in an out of the way place along the frame rail. Leave enough slack for axle droop and make sure you secure it well.

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After that, just pick a spot that's high enough not to suck water. I picked this spot next to the heater fan motor. If the water gets this high, I've got bigger problems than just the rear axle. Add a filter ( I used a Fram G2 fuel filter) so you don't suck too much dust in. Sorry about the picture, the camera wasn't focused enough I guess. Don't forget the front axle, mine has never sucked water for some reason but that doesn't mean it won't. Better safe than sorry.
 

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