[olllllllo]

Okay, whatever. It sounds like you've got a superiority complex about anything other than a Jeep. ...

I think that since this a "Jeep Commander" forum, not a general SUV/Off-road forum you will find that most of us here feel that way.

Actually, I'm a member here longer than any of you that posted so far... and I don't brag about the superiority of the 4Runner.

What does the amount of post you have made have to do with anything. Congrats on that I guess... And contrary to that statement;

It seems like the only system that compares to the 4wd system on my current SUV.

Which I can only assume you are referring to your 4-Runner. Kind of seems like your braging to me... Maybe not, you did say that it compares.

4-Runners are probably great vehicles, just not the kind of vehicle people want to talk about in this forum.

 

[HemiCommander]

Somehow you failed to find any information about the 4Runner's ATRAC system, which is exactly what makes it shift power side to side like the QDII system. It's great to do research, but please make sure it is complete if you want to be an authority on the subject....

T4 - I have searched the net trying to find a good description with not much luck. why does Toyota not have something similar to Jeep explaining exactly how A-Trac works?

The best I could find was from this site: http://www.toyota-4runner.org/showthread.php?s=&threadid=5036 - I have inserted a quote below which attempts to explain how A-Trac works. From what I can tell, I'd rather have QDII - It seems that A-trac would necessitate frequent changing of brake pads. Also, if I am understanding what I am reading, A-Trac only has the capability to "virtually" shift torque from left to right - QDII monitors all wheels and reacts accordingly.

I/We (Jeepsters) welcome your research and thorough explination of exactly how A-Trac works.

Here is the quote from the Toyota-4runner.org site:

"Excellent response! This is commonly mistaken and misleading in a lot of manufacturer's literature, including Toyota and Mercedes (for the ML). ATRAC is there to PREVENT loss of torque to the wheel with traction.

For example, if one wheel (in mud) is spinning on an axle, then the other wheel (on dry land) LOSES it's torque because power is routed to the wheel with least resistance (the one in mud). So, power is being transferred to wheel in mud. Now, with ATRAC, the ABS sensors will sense this slippage and apply the brake to the spinning wheel. It will apply the brake UNTIL the two wheels are spinning at the same speed (in theory)...that is, it will apply the brake to slow the spinning wheel to the same speed as the wheel that is on dry land. By doing this, it tricks the differential into thinking that the slipping wheel is also on dry land...thus, preventing all power from going to the slipping wheel. It evens out the torque distribution to both wheels. This prevents the wheel with traction (on dry land) from losing torque. Thus, it will have power to move your truck forward.

Does ATRAC really allow for 50% split?? Well, in theory, yes. However, in real life, i would say that it helps prevent torque from TOTALLY going to the spinning/slipping wheel. However, because of the stress on the brakes (brakes have to go against the power flow...aka HEAT LOSS) AND powertrain (remember, ATRAC can be quite sudden in it's operation), i doubt it. I would say that it is somewhere less than 50%. That is, ATRAC will prevent most of the torque from going to the slipping wheel. So, the wheel with traction will receive less than 50% of torque, but enough to keep your 4runner moving forward.

Thus, this is the role of ATRAC...it prevents the loss of torque from the wheel with traction...to allow that wheel to get enough power to move your 4runner forward.

This is why the 4runner has big brakes with multi-pistons and 4-channels. You need good brakes in a vehicle with ATRAC for effective ATRAC operation. In addition, 4runner powertrain needs to be beefy to take the stress of ATRAC.

How good is ATRAC?? It is as good as any limited-slip differentials (LSD) on the market. It will only lose to a true locker over rocky terrain, hill climbs, and deep mud. But then again, it is less stressful on the axles than a locker in most circumstances.

With ATRAC, it's like having LSD on the front AND rear axles. With the center diff locked, the 4runner is quite capable! ATRAC is such an elegant and simple design...no extra stuff...it just uses the existing technology (4-channel ABS, ABS sensors, etc.) to create a LSD.

Hope this makes sense...and sorry about the length.

 

[TR4Runner]

What does the amount of post you have made have to do with anything. Congrats on that I guess... And contrary to that statement;

Which I can only assume you are referring to your 4-Runner. Kind of seems like your braging to me... Maybe not, you did say that it compares.

I don't have a lot of posts... I've just been a member of the forum for a long time. Almost from the beginning. The point here is that I'm not a noob to the forum.

And yes, I was comparing the QDII to the system in my 4Runner. That's not bragging. Nowhere did I say that the 4Runner system was superior... just similar.

 

[rubicontrail.net]

T4 - I have searched the net trying to find a good description with not much luck. why does Toyota not have something similar to Jeep explaining exactly how A-Trac works?

The best I could find was from this site: http://www.toyota-4runner.org/showthread.php?s=&threadid=5036 - I have inserted a quote below which attempts to explain how A-Trac works. From what I can tell, I'd rather have QDII - It seems that A-trac would necessitate frequent changing of brake pads. Also, if I am understanding what I am reading, A-Trac only has the capability to "virtually" shift torque from left to right - QDII monitors all wheels and reacts accordingly.

I/We (Jeepsters) welcome your research and thorough explination of exactly how A-Trac works.

Here is the quote from the Toyota-4runner.org site:

Sounds like the A-Trac is what the Patriot uses for directing torque. It is a fairly decent system. However, it means power is being sent to a wheel that is not using it. It is then being braked to keep from unnecessarily spinning. The ELSDs send power only to the wheel that is moving (meaning 100% of the power minus driveline inefficiences are directed to that wheel(s).

 

[TR4Runner]

HemiCommander,

For a great flash presentation on ATRAC, go here:

http://www.toyota.com/fjcruiser/specs.html

Click on "click here to see A-TRAC in action"

For some reason, Toyota put this in the FJ Cruiser section and not under the 4Runner section, although the systems are identicle.

BTW, the system doesn't work virtually... it really works to transfer power from the side without traction to the side with traction. The beauty of the system is its simplicity, as it doesn't require anything other than the regular stuff used in traction control and anti-lock braking. Brake pad wear isn't a concern, especially considering that the amount of braking used is absolutely minimum. I'd guess far less than 1% of brake pad wear could ever possibly be a result of ATRAC.

I recently got back from a bit of a snow wheelin' trip up in Syracuse, NY, and I've gotta say that the system has an amazing ability to let the 4Runner find traction at any wheel. The combination of the locking center differential for power split front/rear and the ATRAC on both axles to handle power split side-to-side makes it nearly unstoppable on snowy terrain.

 

[TR4Runner]

The ELSDs send power only to the wheel that is moving (meaning 100% of the power minus driveline inefficiences are directed to that wheel(s).

Are you sure about that? I don't see how a locked differential (of any kind) can possibly send 100% of the power to just one wheel. I would think that a locked differential would do just that--lock the differential, meaning both wheels on the axle would receive an equal amount of torque.

Does the ESLD actually lock anything, or does it just redirect torque? Either way, the end result is the same in that power is directed to the wheels with traction.

 

[rubicontrail.net]

Are you sure about that? I don't see how a locked differential (of any kind) can possibly send 100% of the power to just one wheel. I would think that a locked differential would do just that--lock the differential, meaning both wheels on the axle would receive an equal amount of torque.

Does the ESLD actually lock anything, or does it just redirect torque? Either way, the end result is the same in that power is directed to the wheels with traction.

The ELSDs are NOT a locker. They are an electronic limited slip differential. You are right, a locker would lock them so they are turning at the same speed. This is fine for rock crawling but awful for on-road use because it will wear out a driveline quicker than anything. Hence why the Rubicon's lockers automatically disengage at a certain speed.

But no, it is not the same. When you direct power down an axle shaft you are losing power efficiency. In the case of the A-TRAC system (and the system in the Patriot) you are still sending 50% of the torque to the left side and 50% to the right (in the case where 100% is being directed to the front or rear). That means 50% of the power is being sent to a wheel that you then apply the brakes on (eliminating wheel spin essentially burning off 50% of your energy). On QDII the power is not sent down the shaft that doesn't have traction. Meaning 100% of the power is sent down the shaft that does have traction. That means 300+ lbs of torque is being sent to the wheel that needs to move vs. 150+. If you are stuck on a rock you would rather have 300+ lbs of torque to kick you over it.

 

[TR4Runner]

Okay, that makes sense. But keep in mind that torque is being split front to rear and side to side. That means the power is already split 50/50 front/rear (with the center diff locked). So even if the QDII system diverts everything to the wheel with traction, it is still only a max of 50% of total engine torque. Unless the center diff has a way of diverting 100% of the power to just one axle (while locked) and the ELSD can then divert that same 100% to just one wheel.

I'm sure even that is more than necessary under most conditions to keep the vehicle moving under low traction situations. Especially considering that torque is multiplied in low range.

 

[jeep5253]

TR4Runner, please go to post #1 of this thread and click on the link and follow the directions that I posted. You can see an animation with narrative that explains the QDII (and all of the other Jeep 4x4 systems).

 

[rubicontrail.net]

Unless the center diff has a way of diverting 100% of the power to just one axle (while locked) and the ELSD can then divert that same 100% to just one wheel.

I'm sure even that is more than necessary under most conditions to keep the vehicle moving under low traction situations. Especially considering that torque is multiplied in low range.

Yes, that is the advantage of the QDII... that is can direct 100% to an individual wheel. It can also simultaneously direct say 50% to the front left and 50% to the rear right if need be, all in milliseconds.

The A-Trac is a decent system. It is probably on par with the 4WD performance of the Quadra-Trac II system. In fact, the new (Trail-Rated version) Patriot uses essentially the same concept as the A-Trac and it has been getting rave reviews on how well it does off-road.

 

[JeepCollector]

Unless the center diff has a way of diverting 100% of the power to just one axle (while locked) and the ELSD can then divert that same 100% to just one wheel.

A locked diff can send 100% to one axle - if the rear is on ice and the front is on rock, then 100% goes to the front (the rear can provide 0 resistance and therefore 0 torque goes to it - or near 0 anyway).

The 4Runner 4x4 system is the same as the QuadraTrac II system on the Commander. The QD II system has a front and rear differential to transfer torque and does not use the brakes to "virtually" transfer torque. Might want to do a little more research...

 

[TR4Runner]

Already looked at the animation. It's a good demo.

Go to the Toyota website I mentioned and watch the demo for ATRAC. You'll see that the combination of a locking center diff and ATRAC on both axles will in fact allow the Toyota system to direct power to the wheel or wheels with traction.

My only claim here is that the QDII system is the only system available on the Commander that will do direct power front/rear and side/side to the wheel or wheels with traction, like the system on my vehicle.

 

[JeepCollector]

My only claim here is that the QDII system is the only system available on the Commander that will do direct power front/rear and side/side to the wheel or wheels with traction, like the system on my vehicle.

That's not true - even the QT I system uses the brakes to transfer front/rear and side/side - like your 4Runner.

 

[TR4Runner]

The A-Trac is a decent system. It is probably on par with the 4WD performance of the Quadra-Trac II system. In fact, the new (Trail-Rated version) Patriot uses essentially the same concept as the A-Trac and it has been getting rave reviews on how well it does off-road.

According to the Jeep website, QTII uses a multidisc clutch pack to transfer power between the front & rear axles. It doesn't appear that the QTII system has the ability to transfer torque from side to side on the same axle, which leaves it at a disadvantage to the ATRAC system.

The ATRAC system uses a LOCKED center diff (not a clutch pack) to equally split torque front & rear, and ATRAC to split torque side to side on both axles. Completely different, in my opinion.

BTW, the Hummer H3 and the Mercedes G both use ATRAC and are both known as very capable vehicles.

 

[TR4Runner]

That's not true - even the QT I system uses the brakes to transfer front/rear and side/side - like your 4Runner.

What? the QTI doesn't even have low range!

Let me clarify:

QDII is the only system Jeep offers on the Commander that has similar abilities to the 4Runner system. This includes the following:

Low range gearing
Locking center differential
Ability to transfer torque from side to side on both front and rear axles.

Thus, my claim that the QDII system is the only system I would choose for a Commander, since it has similar capabilities to the system on my 4Runner.

 

[jeep5253]

TR4Runner, you just don't get it.

TR lives in Georgia so how about some of you GA guys going over and explaining it to him in person? PM me for his address.

 

[TR4Runner]

That's not true - even the QT I system uses the brakes to transfer front/rear and side/side - like your 4Runner.

BTW, I don't see any mention of the ability to transfer torque side to side on the QTI system. Only front/rear, from what I see on the Jeep website. This system reminds me of the 4wd system on a Ford Escape.

 

[TR4Runner]

TR4Runner, you just don't get it.

TR lives in Georgia so how about some of you GA guys going over and explaining it to him in person? PM me for his address.

Actually, I live in New York. Born here, raised here, and lived here all my life. And if you really want my address, just let me know. I'll be more than happy to give it to you.

 

[JeepCollector]

BTCS on QT IIHere is where it talks about BTCS (similar to ATRAC). Remember that's the mid-package on the Commander.

 

[TR4Runner]

BTCS on QT IIHere is where it talks about BTCS (similar to ATRAC). Remember that's the mid-package on the Commander.

Does the system have the ability to lock the center diff? I can't seem to find any Jeep literature that says it does... but I could be wrong. Point me in the right direction...