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Being an off-road enthusiast is not about buying the most expensive overland gear, clothes, and high-powered SUVs and constantly posting pictures of yourself anytime you go off-road. Nobody likes that guy.
Being an off-road enthusiast is about understanding nature, spending time in the wilderness, and conquering it with your four-wheel-drive. It’s about being capable of adjusting to challenging terrain and difficult conditions you encounter and enjoying every minute of it. Also, knowing a thing or two about vehicle mechanics helps.
That being said, today, we will talk about one of the most critical aspects of the off-road driving dynamics – adding gears to your overland or 4WD vehicle.
Off-roading is the only motoring discipline where having a high horsepower engine will not guarantee you success. On the trail, torque is far more important, and in order to utilize it, you will need the right gearing. Ideally, you want a set of gears that will perfectly transmit the torque to the ground and maximize the engine’s potential. Today, we will tell you how to achieve just that.
The Basics
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Before we go into details, let’s revisit the basics. Every vehicle has an engine, transmission, and some kind of differential. The engine produces the revs, which are distributed through the transmission to the differential. The wheels, through spline axles, are directly connected to the differential. This means that differential is the key to understanding the power delivery.
The differential ratio (also known as rear-end ratio) is a numerical value that tells you how many times the driveshaft rotates compared to one turn of the wheel. Having a numerically higher differential ratio makes your vehicle accelerate better but achieving lower top speed. Having numerically lower rear end gearing will result in slower acceleration but higher top speed.
Most vehicles are designed to have the right balance between acceleration and top speeds. This means that their gear ratios are between 2.73:1 and 3.73:1 making it good off the line and capable of decent cruising speeds.
However, if you are serious about your trips to wilderness and rock-crawling, you should consider re-gearing or adding gears to your vehicle, and here is why.
Pros of Adding Gears to Your 4×4
Re-gearing your overland or four-wheel-drive vehicle or truck is a relatively simple mechanical process but will reward you with much-improved driving dynamics off-road.
By installing a numerically higher differential ratio, you will be getting noticeably better acceleration and better access to the engine’s power band. In real-life conditions, especially on the off-road course, you will notice the better throttle response and lively acceleration. This is achieved by better use of the engine’s torque curve.
You cannot change the fact that the engine produces maximum torque at higher RPMs, that is just how internal combustion engines work, but you can change the way that torque is delivered with different gearing. High RPMs don’t mean that the vehicle should go fast.
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In fact, in off-road conditions (rock crawling, sand, mud), you want it to be slow but firm and powerful. Higher gearing will let you use the torque in a more controllable manner, which is precisely what you need on the trail. Using all of your engine’s torque is incredibly valuable if you need to pull a trailer up the hill or get yourself out of a sticky situation.
Lots of off-road enthusiasts install bigger all-terrain tires, which ultimately affects driving dynamics since it affects factory set up. However, if you want a bigger tire but you don’t want any loss in performance and acceleration, installing higher gears will iron out the difference. Also, since the bigger tires have more rolling resistance and wider grip surface, higher gearing will mobilize engine power better to cope with it.Â
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Downsides of Adding Gears to Your 4×4
Of course, there are downsides to this modification, most noticeably, change in vehicle behavior when in everyday traffic.
First of all, you will experience that the engine is revving higher at highway speeds. Since the differential ratio is numerically higher, it means that the engine needs to work harder in order to achieve the same speed. When the difference between stock and aftermarket gears is around 0.5:1, the change is not that significant, but if you radically alter your differential ratio, you will be surprised how different the vehicle behaves.
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Logically, the second downside is the decreased fuel economy. When the engine is revving higher, it uses more fuel. Add to the equation bigger and wider tires you will experience fewer miles per gallon after you re-gear your 4×4. As mentioned before, if the change in gear ratio is not significant, the increase in fuel consumption should not be big.
The third downside is the added stress to the transmission and engine. However, this is highly debatable. Some sources claim that higher RPMs will ultimately cause extensive wear to your engine and transmission instead of the people claiming that this will not happen.
Price of Re-Gearing
Adding gears to your off-roader is one of the more affordable yet more significant modifications you can do. The basic ring and pinion set for Dana 44 axles (standard on Jeeps) start at around $150, while the complete set for front and rear differentials along with all bearings, oil, and seals goes for about $600. Of course, there are more expensive products on the market, but the real question is, do you need to go that far.
Also, if you are mechanically inclined and handy with the tools, re-gearing your truck, SUV, or Jeep is something you can do in your driveway. It isn’t a job for a novice mechanic, but if you have some experience and know what you are doing, you can save yourself a considerable sum of money practicing your DIY skills.