We hear a lot of questionable advice thrown around these days, particularly in Internet forums, where it is often difficult to tell from a username who is a grizzled old wheeling veteran (unless the name is something like WeldsInSandals62) and who is a kid in his parents’ basement who has never even shifted into low range. Instead of just repeating what we read on the web about “Cummings” and “Vortex” engines, we have been there, done that, and have the T-shirt to prove it. So we put together this list to set the record straight on some technical items that you might take as gospel. We tried to avoid subjective matters like “You need Dana 60s for hardcore wheeling” and instead focused on genuine, useful tech. Do you have your own doozies that you would like to dispel? Send them to us at firstname.lastname@example.org.
Myth 1: You can’t Steer with a Detroit in the Front Axle Having an automatic locker in the front of your rig does make it more difficult to turn, but with power steering it is perfectly manageable and with hydraulic assist it is imperceptible. We often see people install a selectable locker in the front axle and an automatic locker in the rear axle, under the premise that the vehicle will turn better. What competition rockcrawlers have learned is that a locked rear axle tends to push the vehicle straight regardless of what direction the tires are turned. A selectable locker in the rear and an automatic locker up front actually provides better turning ability than with the automatic locker in the rear.
Myth 2: Unit Bearings are Junk
Critics will point out that there is no way to replace the bearings in a unit bearing, or inspect them for wear. It is true that you cannot rebuild a unit bearing, but without starting a discussion about our disposable society, we will say that unit bearings have proven to be light, compact, and easy to replace if necessary. Like most parts, the key is to buy quality components, not the knockoffs from overseas. Spidertrax even offers unit bearings constructed from heat-treated chromoly that accept 40-spline axleshafts. If they have to live under a diesel engine, winch, and steel bumper with 37-inch-tall tires and wheels with minimal backspacing, a Dynatrac Free Spin kit is probably for you. Unit bearings are a reasonable choice for the rest of us.
Myth 3: Tubing is Stronger than Solid Rod
This is a topic that usually has a lot of qualifiers, such as “per pound,” which can cause confusion. The strength of a tube is derived from two dimensions: outer diameter and wall thickness. Beyond a 0.500-inch thickness, the strength increase from a thicker wall (all the way up to solid) is negligible. When it comes to bending, the strength comes from the distance of the outside diameter from the center of the tube. Wall thickness provides greater resistance to denting. A 1 1⁄4x0.120-wall tube will have the same strength as a 1-inch solid rod of the same material but will only weigh half as much. And while we are on the subject, DOM tubing is not seamless. It starts as normal Electrically Resistant Welded tube and then is drawn through a tube and die to cold-work it and create a uniform thickness.
Myth 4: Grade 5 Bolts Stretch While Grade 8 Bolts Break
We call this the Butter Bolt Theory, where the claim is that since Grade 8 bolts have a higher tensile strength, they can be brittle. Shear strength of steel fasteners is approximately 60 percent of the ultimate tensile strength, and Grade 8 bolts have a 50 percent higher tensile strength than Grade 5. In addition to greater tensile strength, higher grades of hardware have better shear strength and resistance to fatigue, and they can be torqued to higher values for greater clamping force. The only advantage to Grade 5 is the marginally lower price.
Myth 5: A Spring-over is Cheaper than a Lift Kit
It is true that a new set of spring perches costs less than new leaf springs, but unfortunately spring perches are only a small part of the cost and complexity of a spring-over conversion. In front, the draglink will likely want to share space with the spring during articulation, requiring the steering to be relocated above the springs or at the very least a Z-shaped drag ink (which itself is a bad idea). In the rear, a traction bar is often needed to keep axlewrap to a minimum and avoid breaking U-joints and bending leaf springs. Sorry.
Myth 6: Beadlock Wheels are not DOT Approved
This myth stems from past construction methods where the lip of a conventional rim was cut off and replaced with a beadlock ring. TrailReady, BAD, Raceline, AEV, and Hutchinson all make DOT-approved aluminum beadlock rims that are cast specifically as a beadlock. Additionally, the Department of Transportation does not have any regulations directly related to beadlock rims, but the above rims meet the standards set forth by the DOT. That said, any beadlock rim requires additional maintenance when compared to a conventional rim, and the bolts should be checked and retorqued regularly.
Myth 7: You can Flip a Normal Axle to make it High-Pinion
Reverse-cut (often called high-pinion) differentials are great for decreasing driveline angles and adding ground clearance under your vehicle. These axles have their own design, with ring-and-pinion gears cut the opposite direction. You cannot use a low-pinion gearset in a high-pinion housing, or vice versa. Some confusion comes from the fact that both gearsets use the same carriers. If you tried to flip a low-pinion housing to move the pinion about the axle centerline, it would turn the tires backwards instead of forwards. High-pinion axles also have special oiling features since the pinion does not sit in the gear oil in the axle. High-pinion axles are stronger when used as a front axle than when used as a rear axle because of the gear design, and low-pinion axles are just the opposite: stronger in a rear axle application.
Myth 8: Wheel Spacers are Unsafe
Wheel spacers get blamed for nearly as many problems as President Obama, from death wobble to hashed ball joints and worn-out wheel bearings. They are typically added to widen the track width of a vehicle when larger tires are added and rub on steering or suspension components. In order to remedy the rubbing, your choices are to run either rims with less backspacing or wheel spacers. Neither is a dangerous option, but both can increase leverage and can decrease the lifespan of front-end components.
Myth 9: My Fill in the Blank Would make a Great Engine Swap
Just because you have a Cummins 4BT diesel lying around doesn’t mean that it is the perfect powerplant for the Suzuki Samurai sitting in the back lot with a blown head gasket. In our experience, the actual engine is only a small part of the overall expense once you have factored in wiring, transmission adapters, radiators, motor mounts, fuel delivery, exhaust, and more. The same goes for 2WD to 4WD conversions. If they already offer your vehicle as a 4WD, you are almost always money ahead to sell your 2WD and just buy a 4WD rather than convert what you have.
Myth 10: A Colder Thermostat will make more Power
Modern engines rely on a variety of sensors to determine how much fuel an engine needs to maximize power and efficiency. One of the parameters used is coolant temperature, so the premise here is that by using a thermostat that opens at a lower temperature the engine will run cooler. The problem with this theory is that the thermostat only controls when the coolant begins circulating through the engine, but once the thermostat is open it has no more control over the temperature that the engine runs at, and the temp sensor will read the same value regardless of what thermostat you are running.
Truths you may think are Myths
Truth: Lower Gear Ratios are Weaker
Most people agree on this topic by now, since as gear ratios get lower (higher numerically) there are fewer teeth on the pinion gear. A vocal minority still claims that lower gears are not weaker, but just consider: When fewer pinion teeth are making contact with a ring gear at any given time, the load is spread over a smaller area.
Truth: Electric Fans Free up Horsepower
We have heard people say that the alternator has to work harder to power an electric fan, negating any power gains from the horsepower freed up with the front drive does not have to turn another pulley. But electric fans generally only draw high amperage when they are turning on, and the alternator is already spinning and energized regardless of what accessories are drawing from the system. The amount of gain varies between different vehicles, but it is no coincidence that electric fans are used almost exclusively on all new vehicles.
Truth: Copper Radiators Conduct Heat Better than Aluminum
The thermal conductivity (heat transfer efficiency) of brass is 70 percent, and copper is 92 percent, which is why these materials were used in radiators in the past and are still common in electronics today. Compare that to aluminum, which is approximately 49 percent. So why do we see so many more aluminum radiators on new vehicles and in the aftermarket and so few copper and brass ones? Copper is expensive and heavy, but it also requires that the copper fins to be soldered to the brass radiator tubes with lead solder. This solder has a much lower thermal conductivity than the copper, lowering the overall efficiency of the radiator.
Truth: Synthetic Cable is safer than Steel
While synthetic cable does not just fall to the ground when it breaks, it is 80 percent lighter than steel cable, and as such it stores much less potential energy. Synthetic cable is also safer to handle and does not kink. And while older synthetic lines were susceptible to heavy abrasion and deterioration from ultraviolet rays, the newest offerings, like MasterPull’s Superline XD, address all of those issues and offer breaking strength far beyond steel cable.
Truth: Dana 35s are Weak
Sorry, YJ (and some XJ, ZJ, and TJ) owners. Not only does rear axle only have a dinky 7.6-inch ring gear with 1.18-inch, 27-spline axleshafts, but the axleshafts are held into the diff with C-clips, so when one breaks that whole corner of your Jeep goes off on its own direction, wheel, tire, and all. The aftermarket has parts to address these weaknesses, but you are still left with the small ring gear and a weak housing that is prone to bending. Before investing any money into your Dana 35, consider swapping in a Chysler 81⁄4, Dana 44, or Ford 8.8 rear axle. All offer increased strength with the correct width and bolt pattern.