Brother you’ve got that right. It takes at least two: one with that guy with the white board, and a second one with 3D X-ray animation to see what he’s explaining.

I always loved this video’s simple explanation of a differential.


https://www.youtube.com/watch?v=yYAw79386WI&feature=youtu.be

The Limited 5th gen 4Runner is Full-Time 4wd.

What gives it that ability is that there is a differential in the transfer case which allows the front and rear driveshaft to turn at different speeds.

Using the traditional terms, it is Full-Time 4wd because it has a differential, (which can be locked in the 4Runners) in it's two-speed (high and low range) transfer case.

A vehicle that doesn't have a two-speed (high and low range) transfer case, but can send power to all four wheels, would typically be called AWD.

Anyway, that is how vehicles with variations of "Four Wheel Drive" were traditionally described. The terms have been used and misused, to the point where one has to educate themselves if they care to know the difference.

Great thread. I still after all these years dont get how brake systems send power from one wheel to the other in an open diff.. I thought you need a LSD to get power to the other side. That GM video is a help.

Much appreciated for all the input and perspective here! Love these chats with the community.

Learned a lot, and misspelled axle about a million times. I omitted the gear reduction function, and it being for some, the biggest distinguishing feature of a 4WD, and Full-Time 4WD system. one of the goals of having this conversation was better establishing what full-time “4WD system” means and how for some, these terms are interchangeable with AWD. Thanks to everyone for chiming in and helping work towards that goal! We may not completely see eye to eye on what exactly is featured in the limited’s system. Im speaking specifically about my differing understanding of the way power is distributed (or not) via the brakes on the limited. I know ATRAC does this under 5mph, but not above that, as I feel you;re implying - just as the audi would. im not as certain that this system is on the limited. All the same I appreciate the education on the Audi’s @stiles_s . i still think we got much closer to fleshing out what full-time 4wd means, or is meant to mean vs AWD, and the nuance, (or maybe just my cluelessness, lol). Thanks!

A little more: based on my understanding of an "open" diff, both wheels get power as long as both wheels have traction. As soon as one wheel loses traction, it gets all the power and you... lose forward thrust while one wheel spins. Back in my '60s muscle car days, we'd make fun of the guys who did the one wheel burnouts.

With a limited slip, there is either a clutch setup or a rear torsen (yes, they are used as limited slip diffs too). With the clutch setup it keeps the wheels at roughly the same speed (with some slip) when one wheel slips. Sometimes we'd test for Posi-traction (limited slip) by putting one wheel on pavement and one on the grass and then punching it. Open diff: you'd go nowhere. Posi: both wheels would spin. With a torsen I believe it actually transfers torque to the wheel with more grip (again, example is a rear diff). With either a clutch/disc based or torsen based mechanical limited slip, you'd get two stripes if you did a burnout With too much abuse the discs wear and you eventually have what amounts to an open diff.

With braked "fake" limited slip, it's an open diff, but when that one wheel starts whizzing away (loses grip), it gets braked (single wheel braking due to the wonders of ABS tech) and then power is "forced" across the axle. In this case you'd probably melt your brakes if you tried to do a burnout.... But, it would very effectively get you off of that grassy shoulder.

Yes. One of my opening statements was something to the effect of: “all systems send power to all four wheels until grip is compromised. It’s how each responds that really distinguishes them.” I think there’s a popular misconception that in a traditional 4wd vehicle, only one wheel on each axle gets power. Thats only true when grip is completely lost at each axle.

Is the the “Center Differential” for the AWD on the Limited truly a separate differential (from the transfer case) or merely clutches in the transfer case altering the distribution of power front and back?

This describes the NVG 246 “Autotrac” transfer case in my 1999 K2500 Suburban:

Attached Images

2006_07_10.pdf (1,011.7 KB, 67 views)

Another video on the torsen center diff in the 4r limjted and gx. Planetary gears, not clutches. Too bad Toyota removed it from the other 4r trims in the 5th gen.

https://www.youtube.com/watch?v=pvF_P3vxzGM&feature=youtu.be

Does anyone know if it is physically housed in the transfer case? I would bet it is, but I don’t know.

This guy seems to imply that it is: https://www.youtube.com/watch?v=sOXDMynalbY&feature=youtu.be


Sent from my iPhone using Tapatalk

From info derived in this discussion, its both. Its well-established that there's a torsen t3 center diff on limited. Toyota has referenced it many times. According to @02SE , the torsen-t3 center diff is a component of the transfer case.


@02SE has stated its located in the T/C. Most repair information ive found regarding servicing the center diff is tied to servicing the T/C as well. Would be awesome to have some diagrams to point all this out, but in the absence of that, i think its a safe assumption at this point.

This is a good question. There's some engineering math that explains it. I get the general idea behind the math but can't go deeper than that.

The idea is that with an open differential, both wheels get equal power all the time, no matter what, even if one has no traction. The math goes something like this. It's based on torque times RPM. In the case where you're stuck with one wheel not moving and the other spinning and you're going nowhere, the math is like this:

Stopped wheel:
High torque times zero RPM = zero power

Spinning Wheel:
Zero torque times high RPM = zero power

With zero power to each wheel you're going nowhere fast.

When you brake the spinning wheel, you lower the RPM of the spinning wheel. The driveshaft RPM remains the same. This means some driveshaft RPM needs to go to the stopped wheel. Since it has some torque, once it gets RPM you now have some power on that side.

Yes, the center differential is integral to the Full-Time 4WD transfer case.

Here's a cross-section of a Full-Time 4WD transfer case such as is used in the 5th gen Limited 4Runner:

Attached Images

 

wow this thread has flourished , damn there are some good replies here

*chefs kiss* perfect! Thank you!