We're going to let you in on the secret on how not to get stuck in the mud. The key is not to let any part of your rig-besides the tires-come in contact with the mud. As far as we're concerned, when you are in mud, you never want to dig down into it. You want to skim across the top of it. If your tires dig down, your axles drag through the sticky goo, slowing you down and causing you to dig down more. By the time your transfer case gets in the mud, you're pretty much doomed to a tow strap. Before you know it you've lost all forward progress and dug the tires down deep enough to leave the truck resting on its framerails and you're hopelessly stuck.
How do we know all this? By making lots of mistakes, of course! To research this story we recently took our Ultimate Super Duty (USD) out to Azusa Canyon in the San Gabriel Mountains to see how our 9,000-pound F-250 riding on 46.7-inch Michelins would do in the mud. By no means did we master the mud (or anything else, for that matter), but we did learn a lot about what makes a truck work in the mud...and what doesn't. If you were there you know we broke an axleshaft and a 35-spline hub, smoked our 15,000-pound winch, and had to get dragged to safety. But it was all in the name of research and if you can use what we learned to help you build your own ultimate mud truck, or at least improve what you've got, it was worth it. OK, it was worth it even if our ideas don't help you.
Tires/Wheels/Air PressureChoosing the right mud tires is a matter of matching the size and tread to your vehicle's level of horsepower. The better your power-to-weight ratio, the more aggressive you can get with your tire choice. Tall wide tires that will give you floatation and keep your axles out of the mud are your best bet. Trucks with a lot of power may benefit from a set of Interco (337/334-3814, www.intercotire.com) Super Swampers or Boggers because their fierce paddles and huge voids will move more mud than any DOT tire out there. If your rig lacks power, or you find that Boggers and Swampers dig too much, consider a set of Denman (www.denmantire.com) Ground Hawgs with the less aggressive paddles. You might even try running Boggers in the rear for thrust and Swampers in the front for better steering and to keep the front end floating on top of the mud. No matter what tire you choose, we think it's key to use the widest size you can and run them at a low air pressure, creating the widest footprint. Forget about running tall skinny tractor tires that you hope will dig through the mud to find traction at the bottom. Sometimes there is no bottom. Wheel choice is easier, as it won't matter whether you run a cast-aluminum or steel wheel, but the lighter the better. You might want to consider running bead locks to support the low tire pressures we're recommending because reseating a tire full of mud is next to impossible.
Axles/Differentials/SuspensionThe best axles for your mud truck are ones that won't break during 99 percent of your wheeling, have good ground clearance, and will let you run a locker/spool in the rear, and a limited slip/selectable locker (so you can steer) in the front differential. If you can keep them together, 10-bolt, Dana 44, IFS, portal, or even Ford TTB axles may have an advantage over a Dana 60 because they don't have huge differentials that hang down and drag through the mud to slow you down. Remember, anything that makes contact with the mud (other than your tires) will slow you down and cause you to get stuck. For rear axles all of the full-float eight-lug axles are fine, but the 1011/42-inch 14-bolt gets bonus points for its strength and low price. Equip your axles with gears that will give you power to spin the tires without hitting the engine's redline.
To keep you moving though the goo, your wheels and tires need to be in contact with the mud as much as possible and transmitting power to the ground whenever they are. That means mud trucks should have softer-riding, longer-travel suspensions than other 4x4s because this terrain can require momentum and speed to make it through some obstacles. Soft-riding leaf springs may be the best suspension design for mud because they will tolerate the harsh, wet, grimy environment better than fabricated four-links with coilover shocks and rod ends.
Body/InteriorMud bogging does not require body armor. It requires very little sheetmetal at all if you don't mind getting slimy. Ideally the body of a mud truck would only enclose the engine and driver and concentrate the weight of the truck on the middle-to-rear portion of the frame. You want to keep as much weight as you can off the front end to help the truck float over the mud. Some of the most successful mud trucks don't even run winches up front because they weigh too much. Instead they rely on others or use a rear-mounted winch when they get in trouble.
To build a mudproof interior, the carpet should be torn out and any wires/computers on the floor should be rerouted to higher ground. We like the idea of covering the floor with spray-in polyurethane (it's not just for truck beds!), but a rubber mat or a few layers of thick paint will work too. You're going to be hosing the interior out when you get home, so put a drain hole in the lowest part of the floor to make cleanup easier. If you care about your seats, cover them with a waterproof seat cover like those available from Wet Okole (888/24OKOLE, www.wetokole.com). Even if you don't get stuck yourself, you will be tracking mud into your 4x4 when you get out to help others with trucks that are less capable than your own.
Engine/Transmission/Transfer CaseThe trick here is to have enough power or gear reduction to keep the heavy mud from bogging the engine down to the point that it can't turn the tires anymore. Small-block V-8s won't handle the stress as well as a big-block of the same horsepower level, and they need lower axle gearing to generate the same results. Don't rule out modern diesel engines that are capable of tons of torque (our Power Stroke loves the mud!), but do keep in mind that the extra weight will push the front end into the mud. Fuel injection is nice if you already have it, but we don't think it's necessary for mud. Instead focus on keeping globs of crud from getting thrown onto the air cleaner, or even add a snorkel if you cross through deep water.
As always, transmission preference is up to the driver, but if you run though long bogs and need to shift, an automatic has advantages. Make sure to install an auxiliary cooler where it won't pack with mud, and keep an eye on the ATF temperature with a gauge. Regardless of what kind of transmission you do choose, don't waste your time with an overdrive unit because you won't need it. Take a few minutes to install the factory flywheel or converter dust shield to keep everything clean.
We know few of you will have enough power to spin mud tires in high range so don't go crazy with a 4:1 transfer case, as it won't give you enough wheel speed. And remember to run vent tube lines from all drivetrain components to the highest point in the engine compartment.