Explain the locking differential to a Layman

What does the locker do?

 

In an unlocked, or open, differential, the torque will go to the path of least resistance. Meaning, if you have one wheel on dry pavement, and one wheel on ice, all the torque will go to the wheel on ice, and the wheel with traction on pavement will just sit there.

With a locking differential, both wheels are mechanically locked together by a mechanism inside the differential, resulting in both wheels receiving equal torque regardless of the traction of each individual wheel.

 

So what happens to the front wheels of the 4Runner? What if they are in such a situation?

 

Same thing.

Now this is discounting ATRAC and any traction control features. So technically on the 4Runner, even if both diffs were open, ATRAC will step in and apply brakes to the uselessly spinning wheel, which will help to divert some torque to the wheel with traction, which may be enough to keep you moving.

I'll give you another example of how open differentials behave. When I was a kid I had a '70s Chevy four-wheel drive pickup. Zero electronic features on that at all, lol.

This truck had open differentials, and one time I got the passenger side buried in the snow. Meanwhile, both driver side wheels were on dry pavement. Despite being four-wheel drive, only the passenger side wheels were spinning in the snow, the driver side wheels were just sitting there, not moving at all.

If I had front and rear lockers on that truck, the driver side wheels would have spun at exactly the same rate as the passenger side wheels, despite the vastly different traction that they had. That probably would have been enough for me to be able to drive right out of that, instead of having to spend an hour and a half digging snow out from under the truck in order to get out.

I'm kind of surprised, having owned one, I thought you knew all this. Or are you just getting some conversation going on a boring Friday night? Lol

If you're genuinely interested in things like this, I would recommend checking out some Ronny Dahl videos on YouTube. He's one of those Australian guys, he has a lot of great videos on topics like this.

 

I swear I totally had the opposite idea all this time. I thought that when you locked the differential, then the wheel that was not having traction would be given the whole torque, and the wheel which had the traction would just be told to go to hell
I had my 4Runner for only 2 months, so I didn't get too much time to play with the locker more. The one time that I used it, it kicked ass with street tires.

 

Now another question arises, what is the central differential lock? That Mercedes SUV has it. Does that Locker lock all four wheels to spin at the same time?

 

It is so interesting, that even the best all-wheel-drive systems cannot function like the four-wheel drive systems with lockers and everything. Maybe one day AWD systems will become very advanced.

The new all-wheel-drive system on the RAV4 Adventure is pretty decent, my friend has one of those, does awesome in snow

 

It's a nice little capable and good looking machine.

 

Center differential lock is 4wd. It's only applicable in full time 4wd or AWD vehicles.

Part time 4wd vehicles, like the 4runner (except the Limited) don't have a center differential. 4wd is either off or on.

 

To many, lockers are the single biggest advantage you can have, off road. If you are so inclined, locking the rear, can get you into some serious trouble,... because it will go, damn near anywhere you point the thing. 99.99% of owners wont ever use, nor need the rear locked up. But, for those of us, that damn near bought the thing, because it has a well working rear locker, its the bee's knee's.
(Id love to have a selectable locker up front also)
Dont get over excited, and lock up on pavement. As im sure your aware. Cheers, and happy froading mate.

 

Center differential basically works the same way, except that it locks the front and rear axles together. With an open center differential, you could get more torque going to the front or the rear, depending on traction.

First generation V8 Grand Cherokees were full-time 4WD, similar to a Land cruiser, except they did not have a lockable center differential while in 4high. So, if the front two wheels were in mud, and the rear two wheels were on pavement, it was possible for all the torque to go to the wheels with the least resistance, meaning the two front wheels in mud would spin and you would go nowhere. Theoretically, it was actually possible for all the torque in your 4wd vehicle to go to one single wheel.

Now lock that center differential, and you get 50% torque going to the front, 50% going to the rear regardless of traction. However, if the front and rear axle differentials are open, the torque will still go to the wheel with less resistance. This is why 80 series Land Cruisers that are triple locked are so prized. Not only did you get the 50-50 torque split front and rear, you also got it side to side. (,When all 3 lockers are engaged) Certain generations of the Mercedes G wagon also have this, I'm not sure if the current one does.

Now when you're old 4Runner, that was part-time four-wheel drive, you did not need the center differential. As soon as you put it into 4WD, you had 50/50 torque split front and rear.

Now some people consider the center center diff lock to be an asset while off-roading, however, a locked center diff performs no differently than a normal part-time transfer case. In my opinion, the main asset to having a center differential is the ability to run 4WD on dry pavement. Now not that one would necessarily want to do that, however, in the type of inclement, weather where you go back and forth between snowy and dry pavement, you wouldn't have to worry about switching in and out of 4WD as you would with a part-time system. The Open center differential allows for different wheel speeds front to rear, and does not bind up like a part-time system would.

 

Before I ever actually needed the rear locker, I tested mine in a gravel parking lot. It's impressive to be driving through an area with minimal traction (loose gravel) and still feel the tires binding.

 

Reading all this my love for 4Runner grows even more. What a complete vehicle. Why people spend $50,000 and $60,000 on Acura MDX and other luxury crossovers is beyond me. Get a 4Runner instead

 

They probably could very easily, they're just different applications and as of now the automakers haven't seen a market for it. Most people who want 4WD capability are not buying AWD crossover type vehicles. Some do, but that's not the majority of the market.

 

It is crazy that the new Highlander Platinum cost as much as a TRD Pro

 

You said it yourself, luxury. People buy the vehicle that suits their needs, if you want to go off-roading, a 4Runner is great. If you have no interest in going off road, an MDX, Highlander, etc would be better.

 

Well, other than off-road capability, the Highlander outperforms the 4runner in pretty much every metric. It can even tow the same.

 

Different market, really. To us, crossovers don't seem that great. But, to anyone who's mostly concerned with paved roads, a Highlander is a much better vehicle.

 

Exactly.

 

The thing that is rad, is, its not just that it has a rear locker, its that it WORKS. Adding a locker to set up, will introduce a shit ton of stress to drive line components/shafts/ring/pinion gears/Ujoints, and will very quickly expose any weak points. The ability to lock the rear, at the push of a button, from a oem, is cool. The fact it stays together religiously, and you can 100% count on it,....... is AWESOME.
The amount of snapped shafts, spit ujoints, ive seen, right after some one has lincon locked/poor mans locker (welded) their weak stock dana 30's, or weak 10bolt rears, is insane. Its basically just a matter of time, not if, but when. This rig, i dont even think about it when in the shit.

 

Cool old video on the subject:
https://youtu.be/yYAw79386WI

 

My dad's 3rd gen(1998) 4Runner is approaching 400,000 miles, no major issues whatsoever. 4Runner is a freaking Legend. I've driven it many times and recently, the four-wheel-drive on the thing works like a clock. And the third gen is so handsome.

 

Crossovers have another limitation, wheel articulation. A little uneven surface and boy their wheels are in the air I wonder how they will solve that problem.

No way the RAV4 could do that, right foot up, Left Foot Down

 

Now I know what is that bulgy round thing in the rear of the 4R between the two wheels. The Rubicon has one in the front too, right?

 

Same! And my 4Runner was 6 years old when I bought it, so I was actually just excited that it still worked, lol. I really don't think had it ever been used before.

 

Yeah, that's differential housing, some people also refer to it as the "pumpkin". The 4runner clearly has one in the back, it's a characteristic of a solid axle, and the Wranglers and Gladiators (or any solid axle vehicle I should say) have one in the front as well. The 4Runner actually has one too, it's just a different setup because of the IFS and it's tucked up inside the frame rails.

Also, you were talking about locking differentials, the Rubicon models have locking front and rear differentials. Also the Bronco Badlands, and Chevy Colorado ZR2.

 

But nobody is buying the Rav4 for that.

If we all had the same wants and needs, there would only be 1 model of vehicle available.

 

There are a few SUVs that have low range and independent suspension all around. All of the Land Rover models, and the Jeep Grand Cherokee have that set up. They just make up for it with traction control systems similar to ATRAC. I think in certain years on Rovers you could get an actual locking rear differential, and on the first generation Volkswagen Touareg which had independent suspension and low range, you could get one in the rear as well.

To clarify, in my opinion, a vehicle that has a low range gear in the transfer case is an SUV, regardless of the suspension setup. If there's no low range, then it's crossover.

To muddy the water's a little bit, the new Subaru Wilderness models are fully independent suspension with no low range, and they actually seem pretty capable off-road.

 

Trying to define truck/suv/crossover always brings up problems. For example, with your definition, a 4WD 4Runner is an SUV but a 2WD is a crossover.

 

Yeah, everybody has a different opinion on this.

On a two-wheel drive 4Runner though, there is no transfer case so that's really not part of the conversation.

I was actually going to make a comment about being rear wheel drive based too, but decided I didn't want to get into it.

I guess you could consider a two-wheel drive 4Runner basically like a tall station wagon lol.