Repairs and Maintenance

An Inside Look at Tacoma Differentials

As we all know, a differential can make all the difference when it comes to driving. Given that there are many different types available, we’re going to look at some of the differences between them and compare how they would preform in different scenarios.

Tacoma Differential

What is a Differential and Why Does it Exist?

When your truck’s engine turns the driveshaft and sends power to the rear wheels, that rotation along the driveshaft is basically “turned” 90 degrees and split between the rear wheels. This turning and splitting of power from the driveshaft is accomplished by the rear differential.

On most vehicles, a differential is a compact mechanical gearbox. It’s designed to both channel power from the driveshaft to the wheels, as well as to prevent the axle or the driveshaft from binding when the wheels rotate at different speeds.

This video – which was made perhaps 70 years ago – does a fantastic job of explaining how differentials work.

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NOTE: Skip ahead to the 1:45 mark to see the explanation. Trust us – it’s worth watching.

To summarize, a differential has two missions:

  1. Translate power from the driveshaft to the wheels
  2. Prevent binding when the wheels turn at different speeds (as they do any time a vehicle turns)

The Three Main Types of Differentials:

1. An Open Differential

Open differentials are relatively simple pieces of gear. While they prevent binding in a driveline, they have a serious design flaw in that they send torque to the fastest-turning wheel. This means that vehicles with an open differential tend to “dig in” whenever one of the wheels breaks traction, as the wheel without grip tends to spin faster, and that in turn means more power goes to that wheel (which is pretty much the opposite of what you would want). This is why very few modern vehicles feature an open differential.

Having said that, Toyota has offered something called “Auto LSD” on their trucks in recent years, which is basically an open differential system modulated by traction control. Toyota’s system measures wheel speed electronically, applies the brakes to the wheel that’s spinning faster, and then the “dumb” open differential does a better job of sending power to the wheel with traction.

Functionally, Toyota’s Auto LSD and a real limited slip differential (LSD) generate about the same result…but they are different.

2. A Locking Differential

A locking differential is the mainstay of most truck 4wd systems. They “lock” the two wheels on the axle together, thus making it impossible for one wheel to spin faster than the other. Locking differentials are very valuable off-road, as they’re more predictable and easier to control at low speed.

Most 4wd trucks have a locking front differential as a standard feature. However, some vehicles – like later model TRD package Tacoma’s – have an electronically controlled front differential that can be locked or unlocked as needed.

3. A Limited Slip Differential (aka LSD)

A limited slip (aka LSD or Positraction) differential is designed to send traction to the slowest-turning wheel, the thinking being that the slowest turning wheel has the best traction. This is usually accomplished with a clever gearing arrangement, only some limited-slip differentials use hydraulics or electronics to send power to the slowest-turning wheel.

For most trucks, a limited slip rear differential is a standard feature. On some newer Toyota trucks, the standard limited slip has been replaced with Auto LSD, which is described above.

Tacoma Differential

Which Differential Is Best?

While there’s no “best” differential setup for all situations, there are some reasons to go with one type of differential over another.

If you want to take the vehicle into some seriously tricky off-road conditions, for example, then a locking differential (or even better, an electronically controlled locking differential) would be the ideal choice. This gives you the ability to chose when the differential locks, letting you chose when and to which wheels the traction is applied to. This has slight advantages over the limited slip differential as you can chose where and when the traction is applied.

For normal driving, on the other hand, a limited slip differential (or an open differential with traction control, like Toyota’s Auto LSD system) is just fine. You don’t really need to worry about locking a differential if all you’re going to see is wet or icy roads. Same goes for light-duty off-roading, like driving up a sand boat ramp or tackling a poorly maintained dirt road.

Finally, the most important thing to remember about differentials is that they’re most effective when you’ve got the right tires. If your tires aren’t capable of maintaining traction, your choice of differential is largely academic. Therefore, it’s a very good idea to buy the best set of tires you can for your Tacoma before you start worrying about what kind of differential you have.