We’ll let you in on a dirty little secret. Every modification you make to your rig has a downside. That flexy suspension might work great on the trail but be a handful on the freeway. And those aggressive tires may hook up in the mud but howl like a propjet going down the pavement. What’s acceptable on a flatfender is not necessarily acceptable on a new JK, with higher levels of refinement expected from the new vehicle. Ideally the only downside to a product should be cost. Many high-end products are designed with the purpose of minimizing compromises.
Despite the clickbait title (hey, it worked if you’re reading this online), there aren’t a lot of single modifications that will render your vehicle incapable of safely traveling down public roads. Slower acceleration? Yes. Increased turning radius? Sure. But you can adapt your driving style to compensate for these changes. Most issues compound, though, such as worn steering joints and a bad alignment resulting in death wobble, or drive flanges with square driveshafts creating vibrations.
Here are our top 10 modifications to avoid if you want to daily drive your 4x4 while sipping a latte and streaming music on your way to work.
Drive slugs are simpler and less expensive than quality locking hubs, but they cause the internal components of the front end to turn all the time. This accelerates the wear of axle and driveshaft U-joints, potentially makes steering more difficult with a front locker and increasing noise and vibration if the front driveshaft is not perfectly balanced. Stick with locking hubs if you drive a modified 4x4 on the street.
Welding together the spider gears in a differential is an inexpensive way to ensure that both tires turn at the same speed. Drawbacks include increased tire wear and a larger turning radius, but a welded differential is predictable on the streets. The strength is directly related to the quality of the welding job. Do a poor job and you’ll have to replace everything inside the differential when it lets go.
An old rockcrawling trick is to take two pieces of box tubing that fit inside each other and welding yokes on the end to make a driveline with a super-long slip. Inexpensive? Yes. Strong? Absolutely! But don’t try to drive fast with a square driveline. There’s no way to balance them and you will wipe out your T-case and pinion bearings and seals in short order.
Beadlock wheels have become so popular that many standard wheels now emulate their style. True beadlocks allow you to air down your tires to single-digit pressure on the trail without fear of losing a bead. Weld-on beadlock kits accomplish this just like wheels designed as beadlocks. The differences with DIY kits are that they are often not perfectly balanced on the wheel when they are welded on, and they also don’t center the tire on the wheel rim.
The advantages to full-hydraulic steering include added power to turn big tires, but removing the mechanical system also allows more freedom in suspension design without concern about bumpsteer. Fully hydraulic steering can be driven on the street, but it doesn’t provide the same steering feel and return to center as a traditional mechanical steering box, so your full attention is required at all times to keep your rig traveling straight down the road.
“Wait, my Wrangler came with coils and links,” you might say. That’s true, but lift a TJ over 3 inches with factory control arms and it’s common for the rear end to try and walk under the vehicle when climbing ledges. Even worse are many homebuilt suspensions that just put links wherever it is convenient without regard for length, angle, or vertical separation. If you must build your own suspension, stick to a kit from a reputable manufacturer or research proper suspension geometry so you know where to weld your control arm mounts on the axle and frame.
Some GM trucks came equipped from the factory with a Quadrasteer system, but that doesn’t mean that you can (or should) just add rear steering to your vehicle. While the added maneuverability greatly improves trail prowess, the complexity of rear steering makes it impractical to retrofit onto street-driven vehicles. Leave rear steer for the competition rock buggies.
If you have a leaf-sprung 4x4, go ahead and throw the sway bars in the trash. The internal friction of the leaves provides stability that coil springs lack. If you have coils, coilovers, or air shocks, you will likely want to run a sway bar on at least one end of your vehicle. Sway bar disconnects are a great way to get more articulation on the trail without any compromises to handling on the street.
Older four-speed transmissions like the SM465 and NP435 have a reputation for being bulletproof, and their stubby length makes them perfect for short-wheelbase vehicles. The shifting is far from perfect, though. These transmissions lack an overdrive and in many cases a synchronized First gear. The granny gear is of no use anywhere but the trail, essentially turning these into three-speed transmissions.
Adding water to your tires is an old trick that farmers use to keep their tractors stable. The same applies on the trail, where the added weight down low increases stability and traction. At low speeds the water is all at the bottom of the tire, but as you speed up it goes for a ride. What happens when you encounter a bump or hit the brakes? The water can move unpredictably and cause a loss in handling.