Center differential + rear differential + front differential = confusion!

[badburro]

Help...I admit I am thoroughly confused as to the differentials in the 5th gen T4R. Is the Torsen center diff on the limited better than the part time 4WD rear diff of the SR5 and Trail? From my limited understanding, Torsen is great for hard pavement dry driving, but what about off road on a trail or in the snow? Is the rear diff on the SR5 and Trail "a step backwards" as some posters have claimed? How come people don't mention much about the front differential (is there one???)? And how the heck does the transfer case play into all this? What about "locking" the differential? Does a locked differential allow the front tires to rotate at different rates? Are the front wheels unlocked at all times regardless of the 4WD system?

Feel free to flame me because I don't know this stuff, but I'm asking for help from anyone who is willing to share their knowledge.

Thanks.

 

[Clemsonfan15]

The Torsen basically lets you run 4WD all the time. With the SR5 and Trail 4WD systems you can't take sharp turns, BUT you CAN run it on dry pavement.

The rear locker in the trail locks the rear wheels so that they will spin at the same rate. It does not affect the front wheels at all.

 

[Ryan_S]

Is the Torsen center diff on the limited better than the part time 4WD rear diff of the SR5 and Trail?

Not better as such. Just different. Some would consider it better because you get 4wd all the time, not just when you pull the lever.

From my limited understanding, Torsen is great for hard pavement dry driving, but what about off road on a trail or in the snow?

With the center diff locked the torsion and the manual TC are basically the same thing.

Is the rear diff on the SR5 and Trail "a step backwards" as some posters have claimed?

Rear diffs are all the same with the exception if the TE adding an electronic locker.

How come people don't mention much about the front differential (is there one???)?

There is one and it is the same across the board. The only thing to say about front diffs would be if there was a locker (ala Jeep Rubicon) however Toyota does not offer that, primarily due to the front being independent suspension.

And how the heck does the transfer case play into all this? What about "locking" the differential? Does a locked differential allow the front tires to rotate at different rates?

The transfer case is the "meat and potatoes" of the 4wd system. It controls connecting the front wheels to the back ones. "locking" the diff directly connects the front and rear. "unlocked" in the limited allows the viscous coupling to allow the front and rear to turn at different rates, i.e. When going around a sharp turn.

Putting the SR5/TE in 4wd is the same as locked in the LE.

Are the front wheels unlocked at all times regardless of the 4WD system?

The front diff is considered "open" which allows the front wheels to turn at different rates. I believe there is electronically controlled hub disconnects that engage when you put it in 4wd.

 

[DRC]

Okay, I was typing my reply when I saw Ryan S's pop up...so just to add to what he is saying:

I had the same confusion when I bought my first 4x4. I have an 08 limited so it’s not a 5th gen, but the principle is the same. You basically have 3 open differentials. An open differential allows the wheels to spin at different rates so when you are turning the inside wheel spins slower then the outside wheel. This keeps the vehicle from hopping on high traction surfaces like a dry road where the tires don’t slip. In 4 wheel drive mode, or full time 4 wheel drive, the center differential is again an open differential to allows the front wheels to spin at a different rate then the rear wheels. So when you are in 4 wheel drive and turning each of the 4 wheels can spin at a different rate. Without open differentials you would bind the differentials causing damage.

Now when you are in “all time” or “full time” 4 wheel drive, e.g. open differentials, you can still get stuck because power will be sent to the wheel with the least traction. So you could basically have 1wheel out of the 4 spinning, be it a front or rear wheel. This is where locking differentials come into play.

A locking differential is just that. It locks the two drive shafts together such that the drive shafts turn at the same rate. Take the center locking differential. When the center diff is locked, both the rear drive shaft and front drive shaft will spin at the same rate. In this case if you were stuck you would have 1 front wheel spinning and 1 rear wheel spinning. This is because you still have open differentials in the front and rear.

Same goes for the rear locking differential. Locking a rear differential will lock the two rear wheels so they spin at the same rate. If you had your center differential locked and also had the rear differential locked you would effectively be a “3” wheel drive vehicle, the two rear wheels and at least 1 front wheel. Add a locker to the front differential and you would be a “true” 4 wheel drive vehicle.

Remember when you lock a differential: rear, center or front, you take away the ability for the drive shafts to spin at different rates which is needed for turning on high traction surfaces. So you should only lock a differential when your wheels can slip to release the binding.

I hope helps and makes sense.

 

[03_4x4Runner]

The lack of a torsen center diff on the sr5 and trail is a cost cutting measure by toyota. If you ever has one and then had it taken away you will miss it if you use 4x4 at all. With out the torsen diff when you turn in 4x4 the driveline goes into a bind. This is noticable even on dirt roads. With the torsen diff you can run 4x4 all day long on hard surfaces and snowy roads and not have to worry about it. This is a reason a lot of poeple are complaining about the 5th gens. There has been a lot of features taken away. I guess toyota thought no one would notice and would buy whatever they make regardless.

 

[Ryan_S]

It's not that people wouldn't notice, it's really that most people don't need full time 4wd. I don't need 4wd all the time because I know how to drive. I need 4wd for certain conditions. Not for driving in the highway to work.

If you are someone that needs 4wd all the time then the LE is a great option, just know that there is a cost to everything. The system is more complex, not much but a little bit, and since you are in 4 wheel all the time you will get worse gas milage. That's why they put the big narrow low profile 20s on the LE, to offset the mpg cost of full time 4wd.

 

[badburro]

The muddy water is slowly becoming more clear...

 

[GeD]

Thank you for the info in this tread! very timely for me I just bout a 1998 4runner and my heart sank when I did a sharp turn in the parking lot in 4wd and felt the binding my mechanic tried to explain it but kind of just trailed off to mumbles no doubt he saw the glazed over look of confusion on my face lol
Thanks again
GeD

 

[Deep Snow Commuter]

Torsens, MPG loss and Skinny Tires

We have all heard as a possible explanation for the Conestoga wheels on the newer Limited Editions that Toyota was trying to compensate for the fuel economy loss which comes with all time 4WD.

My question has to do with the 4th Gen 4Runners on which even the SR5 and Trail Edition had the Torsen center diff. They were not equipped with skinny wheel / tire combinations. So one might casually make the argument that "Torsen and all time 4WD doesn't require skinnier wheels / tires..."

Is it that the 5th Gen 2WD 4Runners get better fuel economy than the 4th Gen Torsen equipped trucks? I haven't seen the EPA numbers.

 

[Jhalko]

I have to disagree with folks saying that the full time 4wd and pizza cutters are purely for mileage. I put SR5 wheels and the stock 265 size on my limited and saw zero difference in mileage.

 

[wfo9]

We have all heard as a possible explanation for the Conestoga wheels on the newer Limited Editions that Toyota was trying to compensate for the fuel economy loss which comes with all time 4WD.

My question has to do with the 4th Gen 4Runners on which even the SR5 and Trail Edition had the Torsen center diff. They were not equipped with skinny wheel / tire combinations. So one might casually make the argument that "Torsen and all time 4WD doesn't require skinnier wheels / tires..."

Is it that the 5th Gen 2WD 4Runners get better fuel economy than the 4th Gen Torsen equipped trucks? I haven't seen the EPA numbers.

The 4th gens v6s had a part time system along with a center diff. I think all the v8 versions were full time 4wd with the locking center.

2wd (not 4wd capable) 5ths are going to get better mpg for a couple of reasons. One being that they are almost 500lbs lighter Part time 5th gens will get a slightly better mpg than full time 5th gens when in 2wd mode.

I doub't the limited wheels and tires have anything to do with mpg. They were targeting a demographic.

 

[Masaro]

I have to disagree with folks saying that the full time 4wd and pizza cutters are purely for mileage. I put SR5 wheels and the stock 265 size on my limited and saw zero difference in mileage.

Same here. I put 18" 4th Gen LE wheels and 265/65s and did not notice any difference in MPG at all.

 

[Bilbo]

Help...I admit I am thoroughly confused as to the differentials in the 5th gen T4R. Is the Torsen center diff on the limited better than the part time 4WD rear diff of the SR5 and Trail? From my limited understanding, Torsen is great for hard pavement dry driving, but what about off road on a trail or in the snow? Is the rear diff on the SR5 and Trail "a step backwards" as some posters have claimed? How come people don't mention much about the front differential (is there one???)? And how the heck does the transfer case play into all this? What about "locking" the differential? Does a locked differential allow the front tires to rotate at different rates? Are the front wheels unlocked at all times regardless of the 4WD system?

Feel free to flame me because I don't know this stuff, but I'm asking for help from anyone who is willing to share their knowledge.

Thanks.

No flames. I'll talk about the full-time 4WD with the Torsen differential. About whether full- or part-time is better, you'll get lots of opinions.

The Center Differential. When unlocked, the Torsen center differential sends more power to the axle with traction.

Actually, two things happen with the Torsen center diff. When unlocked, more power is sent to the axle with traction and the front and rear drive shafts are allowed to rotate a different rates. When locked, 50% of the power is sent to each axle and the front and rear drive shafts rotate at the same speed (just like a part-time when 4WD is engaged).

The unlocked Torsen center diff will never send all the power to one axle. The front drive shaft can vary from 53% down to 30%. The default is 40% to the front axle. The ability of the unlocked center diff to allow different drive shaft rotational speeds is what makes it possible for a 4WD vehicle to turn tight corners on dry pavement.

The Front and Rear axle differentials. In 4WD-HI, the 4Runner has the TRAC system for the front and rear axles. This is similar to a limited slip (LSD) system. According to Toyota, "Toyota’s TRAC sensors are activated when one of the drive wheels starts to slip. TRAC limits engine output and applies the brakes to the spinning wheel. This transfers power to the wheels that still have traction to help keep you on track."

In 4WD-LOW, the 4Runner has the ATRAC system, which functions in a similar fashion. Both full-and part-time 4WD 4Runners have TRAC and ATRAC.

Locking Axle Differentials. Only the Trail Edition, a part-time 4WD, comes standard with a rear differential locker. Some people install after-market lockers.

Hope this helps.

 

[wfo9]

Check the date on this thread, I doubt he still needed an answer on diffs... but maybe it will help someone else.

 

[NoDak]

dam that zombie is alive and kicking, should put him on the "walking dead" show.


anyway, I did gleam some great info early in the thread.

 

[Bilbo]

Check the date on this thread, I doubt he still needed an answer on diffs... but maybe it will help someone else.

Guilty! Won't it be great when the 6th gen arrives? Then all the threads will be new again. Assuming you get one.

Actually, I've planned to hang on to my current for a long time. But then I start looking at the resale prices discussed on this forum. I swear some used trucks must be selling for more than new.

 

[Jhalko]

Great info in this thread and half this stuff will get asked in a month or two in a new thread. Maybe this will pop for someone that searches, dont feel bad [MENTION=101428]Bilbo[/MENTION]

 

[3wbdriver]

Guilty! Won't it be great when the 6th gen arrives? Then all the threads will be new again. Assuming you get one.

Lol. My very first post in here resurrected a 3 or 4 year old thread. At least it shows we're willing to search for it. :becky:

 

[CSix]

It's interesting to see people had similar issues and confusion surrounding four wheel drive strategies in 2010... and they still do today. And, there are good people assisting!

 

[JoshKY]

Very informative. I was not clear on the differential differences either.