Fording

The Ocala Jeep Club of Florida

The Science of Fording by Ron Tyrie, II

Jeeps since the beginning of production have been built as capable off-road vehicles. When the US military first put out the call to automotive manufacturers for a vehicle to replace the horse, they gave many guidelines that had to be incorporated into the design. The vehicle had to do many things and it had to have certain equipment. The vehicle had to be four wheel drive, it had to weigh less than a certain amount, it had to have so much horsepower, and it had to be able to traverse streams nearly equivalent to what a pack mule could do. American Bantam answered the call with Willy’s bringing its example to bear shortly thereafter.

War production military Jeeps had an interesting device designed to aid the vehicle to cross deep streams without fear of damage to drive train components. Whenever a GI was presented with a deep body of water that had to be negotiated, he had a lever on his Jeep’s dash that simply read pull for fording. What this lever did was introduce a slight positive pressure on the front-end, transmission, transfer case, and rear-end that would not allow water in. In extreme applications such as amphibious assaults where the Jeep may find itself totally submerged in water, mechanics would coat the entire engine with grease mixed with asbestos fibers shielding the ignition system and other electrical components from failure. To make a long story short, as long as the engine could get air, Eugene’s namesake could practically swim.

When Willy’s decided to introduce the M38 into civilian production with the designation CJ, the fording option was nixed. The reason for its removal was due to the possibility that the lever would not be returned to its original position once it was no longer needed. The engineers rightfully feared that if this valve were kept open, positive pressure would eject lubricants past the seals resulting in worse damage than what would have occurred if a little water got into the system. As a compromise designers kept the Jeep in a configuration where it could accommodate conquering a “reasonable” amount of the wet stuff. However, reasonable to them was water level not exceeding the centerline of the hub.

Maintenance and Prepping for "Unreasonable Fun"

According to the May 1995 issue of Fourwheeler magazine, engineers state that the Jeep Wrangler (YJ) in stock configuration is rated to ford 19 inches of water at a top speed of 5 mph. While 19 inches isn’t all that bad for a stock Jeep especially if you consider that with the addition of a 4” lift + 33” tires, the Jeep can now ford up to 26”. Regardless of that, how did the engineers come up with this figure in the first place? Basically, they calculate the lowest possible point of water entry that has the potential for mechanical damage.

One could fill a book with all pertinent information regarding waterproofing. Due to time and space restraints, I’ll do my best to inform on some basic points that could possibly inspire some brainstorming. Purely as an example, let’s say I have a newly lifted 1993 Jeep Wrangler equipped with a manual transmission and a four cylinder. Ok, the next thing that I personally want to do is equip it for what I consider to be reasonable water fording capabilities. Starting at the front and working my way back, I notice that my good ole Dana 30 front-end has its vent tube extending nearly to the top of my radiator. I don’t plan on water to rise above my headlights, so for the time being, I’d say that it’s good to go. The next thing that draws my attention as I’m working my way to the rear is the engine’s air intake. Extending from the intake’s air filter box is a trumpet shaped device. The minimum that I would do here is remove the trumpet, and install a K&N air-filter. The reason I personally like the K&N is that it will continue to hold its form and filtering capabilities even after it is drenched with water. A standard paper filter just can’t compete with that. However, in the case of the “example Jeep” I’m going to go ahead and install Turbo City’s air-filter relocation kit and have the air taken in above my engine’s valve cover.

Ok, now on to the transmission, hmm, on to the transmission. Wait a minute! Where is my transmission’s vent tube? Searching by hand I find the transmission’s vent is right in front of my shifter. There is no tube connected to it, only a tiny cap that fits loosely. There is a vent tube that runs along the side of my transmission, but that is for my transfer case. I think that all I’ll need here is to pry the small cap off, get a small section of 5/16” fuel line and a three-way tee in order to just attach the transmission vent to the transfer-case vent which finds itself high and dry on the top of the firewall. Taking my section of new vent line, I place it over the vent, not forgetting to use a small hose clamp of zip tie to hold it tight. Next I’ll cut the transfer case’s vent at a point where the new section of line will reach it and connect all three ends to the tee. The only thing left now on my drive train is the rear end, and similar to the front it already has a vent line, which extends high into the Jeep’s fender.

Interior modifications and other things to consider:

The thing to keep in mind when you are planning to delve into water is to expect for a little H2O to enter the vehicle. Water can get in from many different places from the doors all the way to the shifter boots. Simple planning can prepare your vehicle to be filled with water and still not interfere with the normal functions of your Jeep. The first thing to do if you find that your Jeep always gets water inside during a trail ride is to remove all the carpeting. The reason for this is that combined with a soft top and the Florida heat, mildew can easily develop making your Jeep smell rather foul. Not to mention mud is extremely difficult to vacuum out. Once the carpet is removed, the “body plugs” become exposed. These plugs cover up holes in the body whose sole purpose is to eject standing water. Removing these plugs is sort of a double-edged sword. By removing them, water is expelled efficiently. However, while driving in rainy conditions one quickly finds that water can enter through these holes in a fashion reminiscent of the “Old Faithful” geyser.

Shifter boots are another location where water can find its way into your trusty steed. The best way to ensure that this does not occur is to make sure that the shifter boots are free of tears and in as good of a condition as new. Another benefit of a good shifter boot is that it will prevent any more heat from entering the vehicle.

Damage to electronic equipment in Jeeps can become costly. So, plan ahead and keep your CB up and off of the floorboard. Also, if you have an aftermarket ECM, make sure to keep it clear of any water intrusion. While handheld GPSs are convenient, they can also find themselves in certain locations where they can become exposed to the elements, so make sure that they are stowed in a location that will keep them out of harm’s way.

Lastly, here in Florida, water is usually combined with a bottom consisting of mud. So make sure to keep your momentum going and lock those hubs in before you go in. Nothing is worse than falling into a giant puddle while trying to turn that lock-in on the hubs.