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Nuts & Bolts - March 2014

Posted in How To: Tech Qa on February 3, 2014
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Towing Flat
Q: I closely read the Dec. ’13 Nuts & Bolts column about tying down a tow vehicle, as I have been searching for a trailer for my ’76 Toyota FJ-40 for quite a while. But then I realized I need another trailer like I need a hole in my head. My problem is that all my trailers are for my masonry business and seem to never get unloaded for other things. Then I saw the “Splitting the Atom” article with a fine picture of an FJ with a tow bar. I know very little about using these tow bars and the pros or cons of them. I have an ’05 Cummins, so the tow vehicle is not a problem. I mainly would like to tow my rig up to my cabin 70 miles one way on weekends to use for coyote hunting. School me on this subject if you would.
Phil Kendall
Shiocton, WI

A: Tow bars and flat towing have been around for a very long time. Lots of people do it every day, often behind motorhomes. It’s an efficient way to get a vehicle from one place to another because you don’t have to mess with loading and unloading the vehicle from a trailer and you’re not lugging around the extra weight of the trailer itself. However, flat-towing does take a bit of preparation and extra equipment on your rig.

The first thing you’ll need is a tow bar, and they come in a bewildering number of shapes and sizes. Most of the ones you see these days cater to retirees and their motorhome “dinghies” and have all sorts of features like being collapsible. All you really need is a basic tow bar and the brackets to attach it to the bumper. Fortunately the bumper on an FJ is usually flat and strong enough to tow with, so basic angle brackets should be all you need to make a secure connection. Stick to a reputable name-brand tow bar manufacturer, and be sure to use quality hardware to attach the tow bar to the front of your FJ-40. Don’t forget the safety chains, which are required to make a legal connection to any towed vehicle, whether it’s a trailer or a 4x4.

Next up is wiring. You will need to either wire a pigtail into your FJ taillights so that they’ll work when connected to the trailer plug on your truck, or you’ll need some magnetic taillights that you can mount on the Toyota when it’s being towed. Wiring a pigtail into the factory taillights is a much cleaner and easier option in the long run. All you need is a universal flat-four trailer harness (available at any parts store) and some diodes to splice into the Toyota’s taillight harness. Diodes are basically one-way valves for electricity, and they’re necessary to prevent the tow vehicle’s stop/turn/park circuits from backfeeding into the Toyota’s wiring and causing problems. These diodes are available at any store that specializes in RVs and are inexpensive. It will be up to you to identify each of the circuits you need to tap into on the Toyota, but there should be some instructions with the diodes, and the whole procedure is pretty straightforward.

Now we can turn to the mechanical stuff. You didn’t mention what drivetrain is in the vehicle, but we’ll assume stock axles and transfer case. If the vehicle is equipped with a locking steering column, you’ll need to make absolutely sure it’s unlocked when you flat-tow. This can be done by simply using a spare key and clicking the ignition switch to the position where the column is unlocked but not turning on any power to other vehicle systems or accessories. Unlocking the column is necessary so that the front tires will follow the truck when turning; if you forget to unlock the column, you’ll know fairly quickly when the front tires on the towed vehicle start squealing around the first corner.

Perhaps most important of all is figuring out what gear you need to position the transmission or transfer case in when towing. Because the tires of your FJ will be rotating when flat-towed, they will also be driving the axles, driveshafts, and transfer case. The answer to the transfer case/transmission question varies from vehicle to vehicle, but it’s a critical because getting it wrong can cause oil starvation to vital moving components and major drivetrain carnage. For newer vehicles, I recommend consulting the factory service manual or even contacting a dealer. Since that’s not really a good option in your case, we turned to the Toyota transfer case experts at Marlin Crawler ( A representative there said that the safest bet is to unbolt the driveshaft from the rear axle and use a bungee cord to tie it up and out of the way. While placing the transmission and transfer case in neutral would not theoretically cause any damage in your case, Marlin Crawler says that flat towing tends to be hard on transfer cases, and since the driveshaft is held on by just four bolts, it’s the safest bet. I agree. I’ve heard a few horror stories of something going wrong while flat towing and taking out the entire drivetrain of a vehicle. The 10 minutes it takes to unbolt the driveline are worth it when you consider the potential consequences.

One last thing is to observe the behavior of your FJ the first few times you flat-tow it. If it sways back and forth or wants to lock the front tires in one direction when going around a corner, most likely there a caster problem that needs to be addressed. You should also be sure that the tires are all at the same pressure and that the steering components and kingpin bearings are all up to snuff. Sometimes adjusting the toe slightly in or out can calm down a fidgety flat-towed rig. Don’t forget that because your towed vehicle is touching the ground when flat towing, it must be properly registered just like any trailer in most states.

Bump It
Q: I have an ’03 Ford F-250 4x4 with a 3-inch suspension lift and 315/75R16 tires. The question I had was regarding extending the bumpstops and how much to extend them. I like the idea of a low center of gravity while still running a decently tall tire, so I don’t want to lift it anymore. The truck sees moderate trail wheeling and is not a rockcrawler obviously, but I would like to maximize trail performance. I have seen guys extend their bumpstops down until they are very close to touching, or should I just extend them 3 inches to match the lift?
Duane McHenry

A: Conservative lifts with big tires are a popular trend right now, and I wholeheartedly approve! Sticking with a mild lift kit has all kinds of advantages, including easier vehicle entry and egress, better ride and handling, and less complicated lift modifications.

You are right to be concerned about the bumpstops, however, even with the relatively mild lift on your truck. It has always been a pet peeve of mine that lift kit companies often don’t address bumpstop clearance with their lift kits, whether it’s replacing the factory bumpstops with longer ones or simply relocating the existing ones to work effectively with the amount of lift in question. It leaves the suspension unfinished and customers such as you scratching their head. Addressing the bumpstops is one of the indicators of a quality lift kit, and it’s exactly the kind of stuff I look for when comparing one lift kit to another.

Bumpstops serve two functions: They keep tires from contacting fenders under suspension compression, and they serve as a cushion to slow down the suspension as it reaches the limit of its compression travel. In some suspension designs they take an even more active role and almost act like a supplemental spring, but on your truck they’re pretty straightforward. A lift will increase the distance between the bumpstops and their landing pads, which means the suspension has to travel farther before the bumpstop becomes effective. If you’ve added larger tires to match the lift height, it can mean wrinkled sheetmetal if the bumpstops are left in factory configuration.

There are a couple of different ways you can address the bumpstops on your truck. As you mentioned, you could simply lower the factory ones on the frame the same amount as your lift via simple spacer brackets and call it a day. Or you could install extended aftermarket bumpstops. If you want to be a little more scientific about it, however, you can figure out exactly how much to move the bumpstops by cycling the suspension in a controlled environment. To do this, you’ll need a ramp (loading docks are often handy for this depending on their design) or a similar type of terrain that will allow you to flex the suspension a little bit at a time. Forklifts work great for this if you have access to one. Flex out the suspension until either the tires are about to make contact with fenders or the suspension has reached the limit of its uptravel and things are starting to bind up. With the truck flexed out, measure the distance between the end of the bump top and its landing pad. Voilà! You have the measurement you need to make the bumpstops work with your specific vehicle, lift, tire, and wheel combination.

As you make your calculations, don’t forget to take into account that the bumpstop will compress somewhat depending on the material it’s made out of, and that you may need a little more room for the front tires when they’re turned. Universal and application-specific aftermarket bumpstops are widely available, but we’re a fan of using the factory ones if they’re made out of rubber or microcellular foam. Foam bumpstops are especially desirable because they’re very progressive (they get firmer as they compress) and they can withstand impacts for a long time without degrading.

Nuts, I’m Confused
Confused Location
Q: I’m swapping a late-model fuel-injected engine in my truck, but I’m not sure where I should place the computer. Should I put it somewhere that will keep it protected from the elements, such as inside the cab, or is it OK to put it under the hood? I’ve done a lot of searching, but there’s not really a clear answer.
Richard B.

A: Where you need to put the computer depends a lot on the computer itself. While you are somewhat limited by the length of the harness you’re using, the determining factor is whether or not the computer is weatherproof. If the computer doesn’t appear to have a sealed case, such as the computers used with TBI Chevys, then it should be placed in the safest place possible. Usually this means inside the cab, but if you have an open-air vehicle like a Jeep, then we’d recommend putting it up high somewhere under the cowl or in the center console. This will keep it protected from the elements and reduce the chance of its taking a dip if you decide to dive off in a big mud hole one day.

Conversely, if the computer case appears to be well sealed and the connectors have O-rings as well as other weatherproofing features built in, like late-model Chevy LS computers, then under the hood is just fine. While mounting the computer to the bottom of the oil pan probably isn’t a good idea, anywhere reasonably high on the firewall would be fine.

We like to use the donor vehicle’s computer location as a rule of thumb. If the original location was inside somewhere, then that’s where you should put it on your rig. If it’s under the hood, then anywhere in the engine compartment would work. In underhood situations, I still recommend a location that’s going to be reasonably clean and dry. Avoid if possible mounting it in a location where it’s going to be subject to heavy spray from the front tires or down low where it could be submerged.

Submission Information
Confused? Email your questions about trucks, 4x4s, and off-roading tech using “Nuts, I’m confused” as the subject and include a picture (if it’s applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I’ll be checking the forums on our website (, and if I see a question that I think more of you might want to have answered, I’ll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes. Write to: Nuts & Bolts, 4-Wheel & Off-Road, 831 S. Douglas St., El Segundo, CA 90245 fax to: 818.566.8501 Email to:

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