Regearing Guide: The Benefits and the Lowdown On Diff Gears

How often have you wondered what is it exactly that makes a proper off-road vehicle.

It should be an easy recipe, after all: a 4×4 with big beefy tyres, a massive lift kit, rock sliders, an alloy tray and a few other pieces of kit that scream serious off-road action. We’re talking about a vehicle that should fly through just about any obstacle course as quickly as a V8 through a litre of petrol, right?

We’ve overlooked something that’s pretty important here, though: just how well does it actually perform. We’ve certainly checked all the right boxes for the appearance of a real 4WD performer, but maybe we need to roll up our sleeves and talk about the most important piece of the entire puzzle … and it has absolutely nothing to do with appearances. It’s the drivetrain.

Getting in Gear

Let’s be honest: drivetrains – differentials in particular – don’t make very exciting talking points. They’re not glamorous, they’re not even visible, and they really do sound just a bit too technical for most people to want to delve into. Nothing could be further from the truth, though; and nothing can make or break a 4×4 driving experience quicker than what’s happening inside the differential – which is why crown and pinion regearing kits are the off-road accessories that every 4×4 owner needs to consider.

A complete regearing kit is going to contain everything that’s needed to completely regear a 4WD vehicle, including:

• Matched front crown wheel and pinion;
• Matched rear crown wheel and pinion;
• Master install kit for both axles;
• For extreme off-roading, solid pinion spacers to minimize gear separation.

And with their availability in popular ratios like 4.1, 4.3, and 4.56, regearing kits remove the guesswork from attempting to match an armful of differential components that may not be completely compatible.

The question though, is what are the benefits to anyone needing – or even wanting – to spend the time or money on regearing. The answer, however, couldn’t be any clearer.

The Rationale Behind Regearing

Take those bigger, beefier tyres we mentioned earlier: if you can imagine swapping a stock Hilux’s 29” tyre for a meatier 33” tyre, what’s really happening is comparable to changing the vehicle’s factory 3.3 differential gear ratio to a taller ratio of 2.9. It may not sound like much, but what it actually means is that the engine and transmission are not only working harder to overcome the increased weight, mass and friction of a bigger tyre, but using a taller (numerically smaller) gear to do it with. It’s the equivalent of putting bigger wheels on a bicycle and then trying to ride it uphill using the highest gear.

Those beefy tyres – as good looking as they are – have effectively thrown the manufacturer’s optimally calculated performance and economy out the window. Even the speedometer’s not going to read accurately now. Add to that several inches of lift, a host of other bolt-on power-drawing mods and a ton of camping gear loaded on the back, and you’re looking at a vehicle that’ll very likely have trouble getting out of its own way, much less getting itself over the trail … and all while it’s burning more petrol too.

To put it simple, the power’s just not getting to the ground anymore, and even more effort’s being spent to get what is available to the ground. Electing to go with a regearing kit is the solution that gives that performance back.

Forged to Last

When it comes to construction, a regearing kit can be expected to be just as tough as the OEM components they’re replacing. You’re looking at ring and pinion forgings that are:

• Manufactured from 8620 steel forgings;
• Precision machined;
• CNC triple-lapped;
• Heat-treated; and,
• Rockwell hardness tested.

In short, they’re gearsets that are designed to last, plus they’re available for virtually every make of 4WD out there.

(Re)geared for Success

When looking at regearing kits, it’s essential to remember that the heart of every kit consists of a pinion gear that connects to the vehicle’s driveshaft and a crown ring gear that resides inside the differential housing. At their most basic, gear ratios are determined by either dividing the number of crown ring teeth by the number of meshing pinion gear teeth; or, visualizing the number of times the driveshaft rotates relative to the number of times the wheels turn. On that same 3.3 geared Hilux, it means the driveshaft rotates 3.3 times for every time the wheels rotate.

For most vehicles, factory gearing information will most likely be affixed to a tab on the differential housing. Fortunately, manufacturers are generally also very good about stamping gear ratios onto the ring gears themselves. With 4x4s, this can be especially helpful as both front and rear axles need to be regeared; and as can easily become the case with any pre-owned vehicle, there’s just no telling whether a previous owner has been playing around inside the differential.

What’s certain, however, is this: that a vehicle’s guaranteed to perform better across its full operating range after regearing. And for the driver who should happen to decide to go back to stock-sized tyres afterwards, they’ll immediately notice the increase in bottom-end performance with that new gearset as well.

The Conclusion

At the end of the day, regearing underlines the most basic of custom vehicle realities: you can’t make a change to something, without it affecting something else. It means that even the simplest, most common mod an off-roader can possibly make – adding larger tyres – is much more than just a simple tyre swap.

Fortunately, the right selection of off road accessories are able to fix this; although it may not be a mod that most people would feel comfortable making on their own.

When speaking with a regearing kit seller, don’t hesitate to inquire about the availability of local expertise to assist with the installation. They’ll certainly know the folks that know the best products and will be glad to help.

If you haven’t done it already, now’s the time to put regearing on your to-do list. Your 4WD will feel like a brand new vehicle afterwards.