I get a ton of Nuts & Bolts questions each month, but some just keep returning and returning. Rather than address individual readers’ questions, this month I’m going to answer the top eight I see all the time.
Keep those letters and emails coming, because we’ll be back to business as usual next month, and I have a huge list of prizes that I’ll be awarding to each month’s best Nuts & Bolts question.
Q I just bought a (any make and model of 4x4 here), and I want to get into four-wheeling. What is the first upgrade I should do?
A Before you drop a dime on your 4x4 you should roll underneath it. Going four-wheeling is about more than just buying stuff and bolting it to your 4x4. You should really get to know your rig, and a great place to start is in the driveway or garage. Get under there and notice things like driveshaft locations, shocks, springs, engine/ transmission/transfer case height, and exhaust pipe routing. Is this stuff well protected? Is anything leaking? Could a rock smash any of the aforementioned items? If you are driving and come up to a rock or tree stump, could you straddle it with your vehicle? Or should you try to go around it or drive over it with a tire? You need to figure out how low the parts are, if they’re protected, and how well.
Now get up out of the dirt and climb inside that new off-road monster machine. Grab the owner’s manual and read all about shifting into 4x4. Do you need to lock the hubs? Can you shift while moving, or do you need to come to a stop?
Once you’ve read about that, go find dirt or gravel and go through the steps. You shouldn’t drive in high or low four-wheel-drive lock while on a hard surface such as asphalt because the drivetrain can bind while turning. Take some time and get to know your 4x4, how it shifts, how slow it goes in low range, how well it steers in 4x4. Then shift back into two-wheel drive and go home.
At this point you’re almost ready to start off-roading. I recommend you find a buddy with a 4x4 to go with you. It’s always good to go wheeling with a buddy (preferably one with his own 4x4) so you have a spotter, someone to help if there is a problem, and someone to take pictures if you get stuck. Stop worrying about getting stuck; we’re not there yet.
If you have a buddy and you’ve found a spot to go four-wheeling (a local trail, mud hole, and so on) then you’re probably about ready to buy something. Let’s start with a towstrap. But first, while you were checking out your 4x4, did you notice whether it had front and/or rear recovery points? If not, you should get some, at least for one end but preferably for both. Also, order an appropriate towstrap. We’re fond of the BubbaRope (www.bubbarope.com) here at 4WOR, but you can surely find other brands at your local 4x4 shop.
Now that you’ve got a towstrap and at least one recovery point, throw in a fire extinguisher and a first aid kit. I’d expect you could buy all these for a couple hundred bucks. If you don’t have a buddy or really feel like spending some extra dinero, then I see nothing wrong with getting a winch, but as with anything, you get what you pay for. I recommend a good American-made winch for when the going gets tough.
Now the most important thing: Go wheeling. We have many advertisers that will sell you parts to upgrade your truck, but first you need to go drive off-road and start upgrading your off-road driving skills. Get out there and play in the dirt. Start in two-wheel drive and then try for 4-Hi, then 4-Lo. If your vehicle has selectable lockers (like a Jeep Rubicon, Power Wagon, and some Land Cruisers and Hummers) then try them both on- and off-road. The more you try, the more you’ll see what it can or can’t do. Just have fun and pay attention to the trail, your truck, and how it is working. The more you learn from driving, the better you’ll be as your truck grows in tire size gearing and with upgrades—but more on that later.
What Rubber Fits?
Q I have a (any make and model of 4x4 here), and I am ready for some bigger tires. What tires will fit on my 4x4?
A Bigger, more aggressive tires are the epitome of the off-road vehicle. A winch is cool, bright lights are neat, and lower gearing is important, but nothing gives your truck that “I’m ready to wheel” look like big rubber. But looks and performance are two different things. You must decide what you want to do with your 4x4, what type of tires you want (aggressive mud-terrains or more streetable all-terrains), how much you are willing to invest, and how much tire you want.
I usually recommend a mud-terrain tire for off-road use. They have drawbacks in that they are usually more expensive and can have a shorter lifespan than all-terrains, but they work much better over a larger variety of terrain and often have much stronger tread and sidewall construction.
At this point I’m going to send you to our website, 4wheeloffroad.com, to find two specific pages. The first is “How to Measure for Bigger Tires” from our Feb. ’11 issue (“Time, Tires & Tape”). This has a step-by-step procedure to help you determine exactly how much taller and wider a tire you can stuff under your 4x4 as it sits. The next page is the “4x4 Off Road Truck Tire Fitment Guide,” which Feature Editor Ali Mansour wrote for our Nov. ’08 issue (“Just a Guide”). This is a rough guide to help you narrow in on what tires will fit with a certain amount of lift.
level, lift, or trim?
Q OK, I know I can fit bigger tires on my (any make and model of 4x4 here), but I’m still confused. I have heard I need either a body lift, a suspension lift, or to trim. What does this all mean?
A Yes, bigger tires often need clearance. This is to prevent the tires from rubbing the body or frame while you’re driving or under full compression of the suspension. One of the simplest and most common upgrades is a leveling kit. Many 4x4s come from the factory with a slight rake to the body, so if you add a leveling kit (usually a spacer above the front suspension coil or strut) the truck will sit level and can usually clear a slightly taller tire.
Another spacer type of lift is a body lift, but they only work on 4x4s that have body-on-frame construction. Where the body bolts to the frame, there are usually small bushings to keep road noise out of the cabin. Body lifts increase the size of these bushings, in effect lifting the body slightly off the frame a few inches. Body lifts can require lengthening or relocating parts like brake lines and shifter or steering columns that run from the body to the frame. I like to see no more than 2 inches of body lift for off-road use. Anything more than that results in long mounting bolts and unsafe shifting possibilities between the body and frame.
The next type of lift is a suspension lift. The 4x4’s suspension is the spring that supports the body and frame over the axles. A suspension lift uses a taller coil spring, an arched leaf spring, or lower mounting points to raise the vehicle. I like the suspension lift, as it not only raises the body but also the frame to give better ground clearance.
As with anything, there can be a problem with too much suspension lift. Off-road, it is usually good to have a low center of gravity. Oftentimes any suspension lift over 8 inches can harm vehicle handling. Some extremely tall lifts have very stiff springs and can reduce wheel travel, making for a rough ride. Imagine your 4x4 is a pyramid. The taller you go, the wider you should be for more stability. But this can also have issues, as you may eventually need custom axlehousings and you might not be able to fit down the road or trail.
Trimming is when you cut or trim fender openings and bumpers to clear bigger tires. Trimming is a personal decision that many 4x4 owners are not comfortable with, while others are ready and willing to cut with abandon. If your truck is old and rusty around the wheel openings, then trimming may not seem so bad. If it’s brand-new and has a hefty monthly payment, then you may not be as keen on firing up the plasma cutter or Sawzall. I have often found that a lift kit will say it can clear one size tire—say, 35s with a 6-inch lift—but you can often go up 1-2 inches in tire size by slightly trimming the back of the front bumper or by pounding flat the inner-fender pinch seams.
My personal preference is as low a lift as possible, maybe a 1-inch body lift max and some slight fender trimming to clear as big a tire as possible.
Big Tires, Low Gears?
Q So I lifted my (any make and model of 4x4 here), and I went to buy big tires. The guy behind the counter asked me if I was going to regear my truck. I told him I have plenty of gear, I have a recovery rope, a fire extinguisher, a first aid kit, and a full cooler. (That last one was my own idea.) He shook his head and said, “No, I mean regear the axles.”
What is he talking about?
A You’re moving right along with your 4x4, Freddy. Gears are an important consideration when going to taller tires, but let’s lay some groundwork first.
Your engine, when running, turns gears in your transmission. The lower gears multiply the torque of the engine to get the mass of the truck moving. As you go up in gears, the multiplication reduces until you get to a drive gear of 1:1 or an overdrive gear of some fraction (usually around 0.75:1). In your transfer case the gearing is usually 1:1 in high range, but low range increase the multiplication of torque to something lower. Most factory transfer cases range from 1.95:1 to 2.73:1 low range. Some go as far as 4:1 low range, but those are rare. The lower the gearing, the more torque multiplication applied to the driveshafts and down to the axles, which is good for most off-road situations.
In addition to all the gearing in your transmission and transfer case, there are also gears in your axles. These are known as the ring-and-pinion gears, and they have a ratio the describes the number of rotations the pinion (which is attached to the driveshaft) turns for each single rotation of the ring gear (which is attached to the wheels and tires). Increasing the size of the tires requires more torque to get them moving, whether you are in low or high range, so it helps to “lower your gear ratio.” This means you want to increase the number of times the pinion turns for each ring gear rotation. An axle with 3.73:1 gears means the pinion turns 3.73 times for each rotation of the ring gear. If you go to taller tires, you want more rotations of the pinion gear, so you want a higher number such as 4.10, 4.88, 5.13, or 5.38. Going to a higher number is known as getting lower gears.
A simple tire gear calculator is to multiply your new tire diameter and your old gear ratio, then divide by your old tire diameter. Say you have a Ford with 30-inch tires and 3.50 axle gears, and you just lifted the truck to fit your new 35s:
(35 x 3.50) ÷ 30 = 4.08
This is very close to the common gear ratio 4.10, but we don’t stop there. Because you not only have a taller tire but also have a heavier tire and more rolling resistance to get it moving, I recommend you go down at least one gear ratio just to get back to factory performance, in this case a 4.56:1 ring-and-pinion. (If fuel economy is a priority, I would stick with the 4.10 ratio.) If you are going to spend more time in the dirt and crawling over rocks and stuff, then you may go even lower, such as 4.88:1.
To recap, you will need to know your current tire diameter and gear ratio and your new tire diameter to determine what your new gear ratio should be.
Locker or Limited Slip?
Q I went back to the 4x4 shop and told them I need lower axle gears. We discussed the best ratio for my (any make and model of 4x4 here), and as I was getting ready to order they asked if I wanted to keep it open, get a limited slip or maybe some lockers or a spool. I kind of went crossed-eyed with confusion. What are all those things?
A Freddy, now you’re getting to the good stuff. Lockers, limited slips, and spools are some of the most interesting components you can put in your 4x4. In fact, they are what make your vehicle into a true 4x4, where all four wheels are turning and clawing for traction.
Believe it or not, most two-wheel drive vehicles are only one-wheel drive because they have what is known as an open differential in the rear axle. This allows the wheels to turn at different speeds when rounding a corner, but it also sends driving power to the wheel with the least traction. So if one tire is on ice or in mud, it will spin, but the other tire will not, and you will go nowhere. Same thing if your 4x4 has open differentials front and rear. You really only have two-wheel drive (one wheel in front, one in the rear), even when you are locked in four-wheel drive.
To get true four-wheel drive, you need some sort of differential that evenly distributes driving power to each wheel. These are known as limited slips, lockers, and spools.
A limited slip has a system of clutches or gears that notice wheel spin and attempt to lock together both axleshafts for even drive distribution. A limited slip often requires special axle lubricant additive and can work great, but because of the clutch-style design they can wear out or lose their locking ability under hard load, and you may be back in two-wheel drive.
Lockers are the next step up the ladder from limited slips. These are designed to lock both axleshafts together, either automatically or by your selection, to evenly distribute power without clutches to fail. Now, some people get confused by lockers, locking hubs, and a locked transfer case. These are three very different things. Locking hubs are found on some front axles inside the wheels, and they allow drive power to turn the tires. A locking transfer case either locks the case to distribute power evenly to both front and rear axles, or unlocks the case to send power only to the rear axle, or has a variable all-wheel-drive setting. These AWD and 2WD settings are for use on hard surfaces, such as asphalt roads.
Within the locker or locking differential syndicate, we mentioned automatic or selectable lockers. Automatics sense any tire spin and lock the axles together automatically. They can unlock when you’re making turns, but can also produce odd on-road characteristics if the tires are not identical in size, so watch those tire pressures. Selectable lockers use a cable, air pressure, or an electric switch to engage the lockers, allowing zero differentiation between wheel speed from side to side and even power distribution to each wheel, even if one is off the ground. Selectable lockers are better on-road because you can turn them off, resulting in an open locker, but they are often more expensive and rely on cables, hoses, or wires, which can be misinstalled or damaged. Plus, you may simply forget to switch it on.
A spool is a locking device that allows for no differentiation between wheel speeds, and it cannot be turned off. Spools can result in difficult steering and increased tire wear, but they are tough and cheap. Spools are either purchased, or made by welding up the internal part of an open differential, but in that case they are only as strong as the welds and original carrier.
I prefer a selectable locker if the driver is skilled, knows how and when to use it, and can have it properly installed. But an automatic locker is hard to beat for “install and forget about it” off-roaders. Spools are best for 4x4s that only go off-road or drive minimally on the street.
More Power & mileage?
Q I have big tires, low gears, lockers, and a towstrap in my (any make and model of 4x4 here), and now it is slow and gets bad mileage. What can I do to get all that power and economy back?
A Some things are just not possible. Big tires, big fuel economy, and big power are three things that do not like to live happily together, but there is hope.
Big tires are heavier tires and thus have a greater resistance to rolling. Their larger front face reduces aerodynamics too. The requirements to fit big tires often also reduce aerodynamics, in turn reducing mileage. Plus, it saps big power to start turning and continue turning big tires. With correct gearing you can usually get back to near-factory power feel, but it gets difficult as the tires grow. We have found that higher tire pressures can help in mileage numbers though.
The two simplest steps for power and mileage are “air in, air out”. The gasoline combustion engine likes to breathe. The easier it breathes, the better it works, the more efficient it is, and the more powerful it feels. Fresh, clean, cool air and easy-flowing exhaust will help with both steps. Superchargers and turbos can increase power also, but with additional costs to install and run higher-octane fuel.
Additionally, unlocking your front hubs, removing heavy tools and spare parts, and driving slower and less aggressively on-road can all improve mileage.
Reducing weight is also important for power. The less truck the engine needs to move, the more powerful it feels.
Engine swaps are a can of worms I’m not going to get into at this point, but here are some guidelines to consider before you start exploring engine swaps.
1. Just because you have the engine doesn’t mean it’s a good candidate for an engine swap.
2. The Rule of 2: Swapping in a new engine always costs twice as much, takes twice as long, and requires twice the radiator to cool it.
3. Just because a foreign engine runs well doesn’t mean it is right for an American-made 4x4. Yes, it has been done. Yes, they run great. But it’s just wrong.
4. A Jeep 4.0L is a great engine in whatever it came in, but not good enough to swap into something else (not even a four-cylinder Wrangler).
5. If the vehicle you are building is already available from a manufacturer, just sell your project and buy one. It’ll be cheaper. (This also goes for 2x4-to-4x4 swaps.) For example, see No. 4.
6. You will need custom exhaust to make it work and fit well under in the framerails.
7. Before you remove the old engine, take pictures and mark every wire and hose.
8. Don’t be scared of fuel injection if the engine you are swapping in has an aftermarket wiring harnesses available (for example, TBI GM, 5.0L Ford, LS series GM). But be afraid of trying to make a junkyard fuel-injected engine run with the original wiring harness.
9. Oil pans can cause problems with front axles. Driveshafts can cause problems with starters.
9. Swapping to a diesel engine will cost more than you will save by swapping to a diesel engine.
10. GM V-8 swaps are boring, but there is a reason everyone does it. The cool, unusual engine is also expensive to fix and keep running.
Vibration & Wobble?
Q I have been driving my lifted and locked (any make and model of 4x4 here) and wheeling it with my buddies. We’re having a great time. But now for some reason I am beginning to notice a weird vibration. Any idea what that is?
A Vibrations come in every shape and size when you start modifying a vehicle. The original equipment manufacturers (OEMs) spend millions of dollars to alleviate unwanted NVH (noise, vibration, and harmonics), and everything we do, from bigger tires to everything associated with getting them on and working, can add to unwanted NVH. Raising the vehicle can increase driveshaft angles, and this can cause driveshaft vibrations. Worn-out steering or gear-train components from adding larger tires can cause steering vibrations and possibly the notorious death-wobble. And larger tires themselves can cause issues if unbalanced or at low air pressure, or if they’re packed with mud in the wheels or lugs from your latest off-road excursion. There are fixes for almost everything, but the first step is diagnosis. Diagnosis is nearly impossible in the pages of a magazine, but here are some starting points.
Clean the truck well. This will remove mud and dirt, allowing for better investigation. Concentrate on the bottom side.
Air up the tires and look for missing wheel weights if the wheels were balanced. Also notice whether the tires seem to have spun on the rim, as can happen when they have been aired down for off-road use.
Check the driveshafts for loose connections, dents, or worn-out U-joints.
Have someone turn the steering back and forth while you watch the wheels. Is everything turning smoothly? Anything popping or not moving that should be?
Any leaks between gearboxes? That may be a sign that the bolts holding everything together are loose.
Any cracks around the steering box mounts, leaf spring mounts, shock mounts, body mounts, and link arm mounts along the frame?
Check steering knuckle joints and suspension joints for any slop.
The dreaded Duo of Questions: best & cheap
Q My buddy Freddy has a (any make and model of 4x4 here), and I really like it. I want to be able to keep up with him or, better yet, pass him on the trail and in the mud. I recently purchased a (any make and model of 4x4 here), and I want to lift it, lock it, put on big tires, and have more power. What is the best part for each? Also, how can I do this cheap because I am a (student, burger jockey, magazine writer) and have no money?
Freddy’s Friend Frank
A Though I test a lot of parts and see a lot of trucks and wheel (or hike while others wheel) a lot of trails, I still cannot tell you what the best parts are. I have not driven every vehicle, tested every lift kit, nor driven every tire over every terrain, though I’m working on doing just that. Hopefully, I won’t die first.
The best advice I can give you is to talk to guys with similar vehicles and ask them what they have used. Read reviews of parts and ask your local 4x4 shop owner. Discuss what you have learned and take everyone’s advice into consideration. Then go wheeling with your stock vehicle, learn to drive it the way Freddy did, and you’ll quickly find out what parts you need to upgrade from there.
As for how to do it cheaply, I’ll start by saying four-wheeling isn’t a cheap hobby. It can be done inexpensively and on a budget, but if you want a cheap hobby, try Frisbee. Watch classified ads for slightly used parts, build stuff yourself, and buy the best parts you can afford. Slowly but surely you’ll have a good truck. I always recommend buying American when possible, but that’s more a patriotic feeling than anything else, as I do number a Toyota amongst my other old battered 4x4s and it’s a pretty darn good truck.
Also stay in school, get a degree or three, study a little business, and work hard wherever you end up. If you become a doctor, spend your coin in the four-wheeling community instead of golf. If you’re a fabricator or 4x4 mechanic, build cool stuff. And don’t knock the new guy getting into the sport, as he may be a doctor with a lot of money who just wants to go four-wheeling.