Off-roading is a heck of a lot of fun. The thrill of hitting the rough paths and letting a beautiful breeze flow through you gives you goosebumps. But it’s all fun and games until you get stuck. Yup, it happens, and this is where you remember there’s something called a diff lock for off-roaders.
Most trucks use a locking differential or simply diff lock to maintain traction, especially on muddy, snowy, or rough roads. And because the choice of which diff lock to have depends largely on you, it is important to know which truck has which differential.
If you prefer a rear locker, or how a truck that has it performs, then this article will give you some insight.
What Trucks Have a Rear Locking Differential?
Most trucks, particularly the 4WDs come with a diff lock either at the front, rear, or center, but traditionally, two-wheel-drive systems have a differential in the rear axle because they are mostly either front- (FWD) or Rear-wheel drive (RWD). However, some modern 4WDs, such as the Toyota Tacoma and 4Runner (TRD Off-Road and TRD Pro trims only), Ford F-series and Ranger trucks, GMC Sierra AT4, Chevrolet Colorado ZR2, Dodge RAM 1500, among others, have a rear diff lock.
Despite these configurations, where to install diff locks in your truck is an option, thanks to the serious upgrades and enhancements modern vehicles have seen in recent years. But why would you need one in the first place?
What Does a Rear Diff Lock Do?
The working concepts of a rear locker cannot be fully fathomed without understanding what a differential in a vehicle means. Well, if you have a penchant for off-roading, your vehicle’s differential system will send power to the wheels to control how they behave under certain conditions, such as when you are stuck or driving on snowy or a slippery surface.
In what is referred to as an open differential system, your vehicle will always send power to the wheel that requires the least resistance, so, if your truck loses traction in such situations, the tire with the least traction will rotate ineffectively.
Getting unstuck won’t be easy, since the torque required by the stuck wheel with better traction to lift your vehicle is shared with the stuck wheel. With a diff lock, however, you can lock the axles together and drive more power to the wheel with better traction to get you unstuck.
This means that unlike in an open differential, during turns when traction is needed, a diff lock will have your truck’s wheels spinning at the same speed by mechanically locking the axles. As such, if you ever found yourself in a situation where one of the wheels is suspended, that wheel will not receive any torque since there is no traction. This will allow your vehicle to move.
Rear Diff Locks on Trucks
Rear diff locks, as I’d mentioned earlier, are popular in 2WD vehicles and some modern 4WDS. The term 4WDs, however, may be taken to mean that all 4x4s drive all four wheels all the time. There is a bit of truth to that, but that applies to full-time 4WDs or All-Wheel-Drive vehicles, and they use a center differential system to keep the vehicle on the road.
Part-time 4WDs, however, do not have that luxury. These types of vehicles are also known as selectable 4x4s since they can drive either in four-wheel-drive or two-wheel-drive. Although they are capable of being driven in 4WD, it cannot happen on-road. Instead, it drives on surfaces with better traction in 2WD, which for these 4WD vehicles usually means using the rear-drive.
Some of the popular part-time 4WDS include the Nissan Patrol GU, Toyota Fortuner, Isuzu MU-X, and Toyota FJ Cruiser, to name a few. Also, almost all utes except for the Defenders and Amarocks are part-time 4x4s. And the main difference between them and the AWDs is that they drive just the rear wheels on-road.
Now, is it such a big deal? That’ll depend on you, but here is some more insight while driving in the real world.
Driving in the real world
On roundabouts, especially the wet ones, and slower corners, your truck will begin losing traction at lower speeds. In such a scenario, your truck is left wanting traction, with some bit of increased rear wheel spin, and maybe with the current powerful engines. This is not such a huge drama today because the modern tech equipped in such vehicles may come with stability and traction control.
Still, with your truck’s rear diff lock, you can adjust the amount of power the outside and the inside wheel receives to better handle such a terrain. After the immediate problem has been solved, you can revert to open differential because you are on open roads.
Note that leaving your rear axle locked on a road with good traction may lead to some problems. Excessive pressure will be applied on your tires, the axle, and suspension, which could lead to damage.
Compared to a full-time 4×4, this whole process seems a little complicated. The 4WD will usually apply the center diff to channel more power to tires with more traction to get you out of the tricky situation. The good thing is that in both, even some 2WDs, the diff locks are automated, and they kick in when needed and disengages on better roads.
Driving on a road with traction also has better fuel efficiency compared to the full-time 4WD. More fuel is required to power all the wheels. In a 2WD, the drivetrain is focused only on the rear tires, which gives the front ones the push they need.
Does Diff Lock Position Matter on Trucks?
For those wondering whether to have a locker at the front or the back, the answer boils down to your vehicle. For example, if your truck comes with a conventional open-center diff at the rear, it would make more sense to have a rear diff lock as it’s more suited to a vast range of off-roading situations.
On the other hand, if your vehicle comes with a limited-slip differential (LSD) from the manufacturer, a wise decision would be to have a locker at the front and leaving the rear unchanged. An LSD’s job is to channel power away from a tire with less traction towards the opposite wheel on the same axle.
According to some experts, having a rear diff lock has more value, thanks to the flex it gives the rear suspension, allowing the vehicle to maintain contact with the ground. This is mostly all that is required to keep the momentum going. But others advise that if you are going hill climbing with your truck, or if you are struggling to get through your last bit of a muddy hole or the ledge of rock, a front diff lock is perfect.
Nevertheless, I wouldn’t forget that front diff locks can restrict how you steer your truck when the weight is over the front axle. This usually happens when you are on flat ground or going downhill. It is, therefore, recommended that if you cannot afford to use rear differentials, at least you should be careful when using the front ones.
Of course, you can also choose to have them both since it is entirely possible. While a locker on one axle gives you a negligible amount of the drive you need for the much-desired momentum, having diff locks on both axles will provide you with 100 percent drive!
Manual or Selectable Rear Locker?
Diff locks can be manual or selectable or automatic. The main difference between a manual and an automatic locker is how they are controlled. The manual one gives you control, but with the automatic type, the vehicle itself manages how it behaves under strenuous situations. Knowing when to activate and deactivate a diff lock is of utmost importance because it can release the stress built up by the vehicle’s drivetrain.
The driver-operated diff locks are engaged from a switch inside the truck and usually on the dashboard. They also require an onboard air supply for the function. The main benefit of this type of differential is that you remain in total control of the lock-up, and you can easily deactivate it when necessary.
The automatic diff lock, on the other hand, is locked when both wheels are making a turn at the same rate of rotation. It is activated or deactivated when during a turn, the outside wheel spins faster than the inner wheel. This increase in speed causes the internal mechanism to release power to that wheel. During the process, there is no time that a wheel can be driven faster than the differential center. The only thing that can happen is for the wheel to freewheel faster.
Meanwhile, as this happens, there is no external source for engaging the process it requires. And that is the biggest advantage – it doesn’t rely on the driver. In other circumstances, the automatic diff lock is quite disadvantageous particularly when wheels begin to lock and unlock alternatively as you circle through various corners or bends. This can cause some unpleasant noise, and sometimes backlash.
Also, the design of most automatic diff locks has become the culprit of most on-road behavior. Since they may constantly lock and unlock, they eventually lead to unnecessary wear on the vehicle’s suspension, engine, and axles, as well as the tires.
Well, there you go. A primer on everything you need to know about rear diff locks on trucks. Hopefully, this article was resourceful. Even if you don’t own a truck with a rear differential, you will at least know how driving one feels like as well as how it functions.
The key takeaway is for you to remember that most trucks with rear diff locks are rear-wheel powered – that is the drivetrain is in the back – and to better utilize it for off-roading, you can engage the differentials to handle tough terrains.
The only thing that will limit you is the kind of task you use your vehicle for. But regardless of whether it is for towing trailers, farming activities, going on road trips, or carrying other heavy loads, you can always find a truck with a rear diff lock that can handle that task.
Better yet, you can choose to upgrade it and install the front diff as well! Meanwhile, here is a resource for more insight on off-roading with your truck.