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Nuts & Bolts - March 2014

Tow Bars Flat Towing
Trenton McGee | Writer
Posted February 3, 2014

Your 4x4 tech questions answered

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 (www.marlincrawler.com). 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.

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