From Dale Wickell,
Your Guide to Trucks.
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Your truck's transmission, transfer case, and front and rear differentials must be vented to compensate for changes in air pressure as temperatures go up and down when you drive, but when you're off-road in wet conditions the most likely place for water to enter is through those vents. Water that gets into vents contaminates the lubricants that protect parts, and that can lead to bearing and gear damage as well as total failure of the component.

The solution--keep water from getting into areas where it shouldn't be. It's not that difficult. Use this easy technique to set up your truck to drive off-road in water and mud.

Elevate the Vents

Before you go off-road, you'll attach tubing to at-risk vents, then extend it to a high location on the truck. Use rubber hose, such as vacuum hose, to vent each component. The total length of tubing required depends on your vehicle, but 12-15 feet is probably enough to extend all the vents.

Before you begin, locate the vent on each component. Determine if each vent is a tube or a cap-type vent before buying supplies.

Tube Type Vents

Buy rubber hose that fits snugly onto vent tubes. You'll need to secure it to each tube with a small hose clamp, leaving excess hose length to route it upwards.

Cap-Type Vents

These mushroom-shaped vents usually screw-in. Remove the cap from each one by unscrewing it. Take the cap to an auto parts store and buy a nipple-vent with the same thread size and pitch. Replace the cap vent with the nipple.

Buy rubber hosing that fits snugly over the new vent tube and secure each location with a small hose clamp, leaving plenty of excess hose length.

Routing the Tubes

Transmission & Transfer Case Vents

1. Route the hose from the transmission and the transfer case along the frame or body to the firewall.

2. Secure the hose with clamps or wire-ties along the route as necessary.

3. Bring the hose to the upper area of the firewall and secure again, leaving a 4-5 inch tail.

4. Bend the tail into a downward curve--like the top of a walking cane--and secure it near its end to keep the curve intact. Check to make sure the hose isn't pinched shut along the curve.

Front Differential Vent

1. Route the hose from the front differential to the frame, allowing enough slack for axle movement. Secure as necessary.

2. Bring the tube up the engine side of the radiator for support, attaching it as high as possible with a clamp or wire-tie.

3. Leave a tail again, then curve it downward and secure its end.

Rear Differential Vent

1. Route the tube from the rear differential to the frame, allowing enough slack for axle movement. Secure as necessary.

2. Bring the tube to the front of the truck bed, then up between the bed and the cab to a point where you can secure it to the bed with a wire-tie.

3. Leave a tail again, then curve it downward and secure its end.

Check All Tubing

Check the tubing to make sure it's free of kinks and positioned away from hot exhaust or engine parts. Now you're ready to go through creeks and mud holes with very little chance of water entering the vents.

Remember that water can enter components through other routes, so be sure to check the color of your differential grease and transmission fluid after each water excursion.

Detecting Water:

• Axle grease turns light brown--like chocolate milk--when it's mixed with water.

• Automatic transmission fluid turns pink when mixed with water.

Most manufacturers recommend you check the wheel bearings if you've been in water deeper than the hub. Re-pack the bearings if there's any sign of water entry.