Upgrading your gears and adding locking differentials can help maximize your adventure vehicle’s off-road capabilities
There’s no denying the penchant that most of us have for modifying our vehicles. Aside from the obvious benefits, there is also the aesthetic aspect of tricking out or building up a favorite overlander. Big tires, lift kits, light bars and bumpers all have their place, but what about the unseen modifications? They may be even more important than the ones we can show off at the trailhead.
Weighed against our love of all things that look cool, the initial cost of re-gearing and installing lockers presents a dilemma on how to spend hard-earned dollars. These upgrades are not cheap and it’s extremely important that the work is done correctly. Installing lockers and re-gearing a vehicle will make it perform better on and off the pavement, help you tackle harder obstacles and even improve performance and gas mileage, but is it right for you? If your tires are larger than stock, the answer is probably yes.
Installing differential lockers such as ARB Air Lockers gives you the ability to physically lock the wheels together at the differential so they turn at exactly the same time and speed. We’ve all seen what happens when you try to navigate a rutted section of trail and weight is shifted around, resulting in tires that just spin and tires that receive no power. That’s called an open differential. Each wheel is free to turn and spin at its own speed. That’s exactly how it’s designed and it works perfectly until you need power to the wheel that isn’t doing anything in the dirt. An open differential is designed to allow both wheels (front or back) to spin at different speeds while still transferring power to the wheels. When you make a turn, the outside wheel needs to spin faster than the inside wheel because it’s covering more distance.
Locking the wheels together at the differential forces them to spin at exactly the same speed. That’s great for getting yourself out of that rutted section, as power is being applied evenly to both wheels, but it presents a real problem when you’re trying to make a tight turn and both wheels are trying to spin at the same speed. Attempting a tight turn with the front differential locked will result in a broken axle or severe binding and scrubbing. This damages your equipment and tears up the trail. An ARB Air Locker allows you to instantly lock the wheels together at the differential and apply power to both wheels simultaneously. Once you’ve cleared the obstacle or section of trail, you’re able to instantly unlock the differential and allow all wheels to spin independently of each other again. You can choose to install a locker in either differential, or just one. Since installing a locker requires disassembling the differential, that’s the best time to address the gearing issues created by installing larger tires.
As soon as you install larger tires on a stock vehicle, you’ve essentially changed the gearing. Going from a 31” tire to a 35” tire will result in what feels like a huge power loss. It represents a 13% increase in gearing which can require as much as 10 additional seconds to go from 0-60. It’s not the lack of power but the lack of torque that we notice. While faster 0-60 times are not overly important to us as backroad travelers, that loss of torque can make a profound difference when climbing hills or obstacles. Installing lower gears into the differentials is the most beneficial way to allow the vehicle’s drivetrain to operate as it was originally designed. Re-gearing can bring back the pep lost after installing larger tires and improve gas mileage by allowing the engine to operate at optimum RPMs.
When it came time to re-gear our vehicle, we sought advice from Carl Montoya, owner of Nitro Gear and Axle and Just Differentials. Carl explained that the general perception is that only the rock crawling crowd needs to worry about lockers and gears, but that simply isn’t the case. Most of today’s vehicles, especially the newer vehicles being used for overlanding purposes, are equipped with very tall overdrives and gearing from the factory. This means better fuel mileage and evenly distributed torque to soccer practice and the grocery store, but doesn’t transition very well to larger, heavier tires, and gear strapped to every free inch of space on the roof rack. “Whenever you increase tire size, you should consider re-gearing. It’s the only way to regain lost RPMs, and improve performance, drivability and fuel economy,” Carl explained.
Not only will re-gearing benefit low-end performance (torque) and relieve the strain on the transmission and other drivetrain components, it will also improve highway driving. With the RPMs in optimal torque range, vehicles equipped with automatic transmissions won’t be constantly “searching” for the right gear to maintain a steady speed on the highway. If you’re shifting for yourself, this becomes even more of a hassle, as you’re constantly depressing the clutch and shifting gears just to maintain a steady speed over a small rise on the highway. Again, re-gearing allows you to maintain a steady pace and causes less wear and tear on your drivetrain. Few modifications to our vehicles can actually pay for themselves over time, but re-gearing is one of the few mods that make perfect financial sense.
For my personal vehicle, a 2004 Toyota Land Cruiser, I chose ARB Air Lockers and Nitro Gear 4.88 gears. The stock gearing for my Land Cruiser is 4.10 and I went from a 31” tire to a 35” tire. The larger tires had a profound effect on my ability to maintain speed when driving the highways. The Land Cruiser is known for having weak front differentials, particularly the ring and pinion gears. I had the unfortunate experience of breaking mine on a mild trail far from paved roads or recovery vehicles. Since upgrading, I’ve drastically improved the strength of the Land Cruiser’s differentials and I’ve also made my vehicle drive like it did in stock form. My fuel economy increased by 2 miles per gallon as well.
Installation cost and lack of understanding are the usual impediments to adding lockers and lower gears, but when you examine the benefits, the modifications should be very high on the priority list. This is even more important on vehicles that are susceptible to differential failure. The cost of recovering your vehicle from a remote area due to differential failure can be high. Strong gears and lockers from manufacturers such as Nitro and ARB will give you peace of mind and improve your vehicle’s ability to handle a wide range of situations on and off the highway.
Resources:
www.arbusa.com
www.nitro-gear.com
OutdoorX4 Magazine – Promoting responsible vehicle-based adventure travel and outdoors adventure
