How important is locking rear differential?

[03_4x4Runner]

You're cherry picking the situation. On uneven surfaces where one tire gets traction for a split second before losing it, ATRAC can be a hindrance. In the 4th gen (non Trail Ed.), the ATRAC acts slow and does not aggressively brake the slipping/spinning wheel to a full stop for any length of time. In addition, the "regular" ATRAC is less effective when you're going slow/crawl because the speed differences b/w the tires on the same axle is less...thus, ECU takes a longer time to react to terrain changes.

With A-TRAC (the FJ and 4runner Trail), there is an actual button that you have to press while in 4-LO to activate it. FJs and 4runner Trails have the "regular" ATRAC system, just like any other 4th gen 4runners...but, by pressing the button, the system ECU goes into the more aggressive mode (again, ONLY in 4-LO). It will aggressively and quickly halt a spinning wheel as soon as speed differences occur b/w tires on the same axle. And this 4-LO only system (A-TRAC) is programmed/optimized to work when you're crawling so that torque transfer occur more quickly despite the slow speed.

I have seen both a 4th gen 4runner (non Trail) and a FJ go up the same path...significant difference. The A-TRAC (4-LO) system makes a good argument to not get a locker! My whole group was quite impress with it.

Now, is A-TRAC (4-LO) a substitute for a locker? For me, no...simply because, no matter how aggressive it is, it is still a reactionary system. But, yeah, it is pretty damn good. A locker allows you to cruise smoothly thru an obstacle/terrain with minimal loss of momentum (as compared to traction control-based system).

For me, once you've experienced what a locker can do off-road, there is no going back. Traction control systems are very good for what it is, but if you want control, smoothness, constant torque delivery to the appropriate wheel(s), then a locker is THE answer.

But, going back to OP, i agree with you JB...he probably does not need a locker. That is why I suggested a locker ONLY if he has the funds for it. In addition, if he ever decides to do more aggressive off-roading, then a locker is there for him to take it to another level.

PS> remembered after looking at JB's signature...i would get a nice pair of sliders too!! A must-have IMO!

Did you look at my videos from my post on the 1st page? You can see that the atrac is inconsistent. Works great at times but not always there when needed mainly when a tire is in the air. This was going up a hill that was steeper than the pictures make it look.

 

[Thai]

Did you look at my videos from my post on the 1st page? You can see that the atrac is inconsistent. Works great at times but not always there when needed mainly when a tire is in the air. This was going up a hill that was steeper than the pictures make it look.

Yup. It goes back to what i wrote above. V8 power does not mean that you can overcome ATRAC deficiencies in certain situations. ATRAC, be definition, lags in reaction time...thus, all that torque will just go to waste in the spinning/slipping wheel and when the wheel with traction gets the power, it may already be too late due to loss of momentum. ATRAC works great when you are going on level ground with good momentum. However, when you're going slow up uneven terrain (with wheel in the air), then this is where the regular ATRAC system can show its limitations with hesitation and loss of momentum.

In other words, if ATRAC on non-Trail 4th gen was so good for off-roading, then why did Toyota went out of its way to offer a driver-selective button for a more aggressive 4-LO-only A-TRAC version (and add a rear locker in the process) on the 4th & 5th gen Trail Edition and FJ Cruiser?

 

[JB.]

Check out the vid in this thread. This does all the describing for me.

http://www.toyota-4runner.org/off-roading-home-monst4rs/83301-short-vid-argentine-pass-atrac.html

 

[Thai]

Check out the vid in this thread. This does all the describing for me.

http://www.toyota-4runner.org/off-roading-home-monst4rs/83301-short-vid-argentine-pass-atrac.html

Exactly...notice that he lost momentum...notice that ATRAC did NOT stop the slipping wheel much at all...it only slowed it down somewhat in pulses. Did he make it up? Yeah, but it was far more eventful than it needs to be. Add more incline to that and he would have much tougher time.

See the difference:

http://www.youtube.com/watch?v=Ot0ve-SsjHo&feature=related

FJ Cruiser - Falcon Hill, Sept 2011 - YouTube

Stock FJ Cruiser Big Flexing - YouTube

My FJ on 3 wheels - YouTube

Watch the front wheels on these videos...notice that the 4-LO only A-TRAC is pretty aggressive...not much spinning is allowed...and it works very well at SLOW crawling speed...something that the "regular" aTRAC is weak at. With the regular ATRAC, you need to maintain enough speed (punch the gas pedal more) so that there will be enough speed differences b/w the tires (on the same axle) for the regular ATRAC to work. Doing this off-road is not really a good thing...because more speed = less control over your vehicle = asking for more damage/carnage.

JB, i know that you like your ATRAC, but until you see an FJ equipped with "super" A-TRAC, you just have to trust me AND Toyota. There is a reason why Toyota gave FJ Cruiser (and Trail Edition 4runners) the ADDITIONAL off-road tool with a separate button to activate it. It was not marketing.

 

[KCcarguy]

I don't know, but I know that the Trail has it.

All 5th gens have the ATRAC button that can only be used in 4LO; so I guess it's the same? :shrug:

 

[Thai]

All 5th gens have the ATRAC button that can only be used in 4LO; so I guess it's the same? :shrug:

Vey cool!!!

 

[JB.]

JB, i know that you like your ATRAC, but until you see an FJ equipped with "super" A-TRAC, you just have to trust me AND Toyota. There is a reason why Toyota gave FJ Cruiser (and Trail Edition 4runners) the ADDITIONAL off-road tool with a separate button to activate it. It was not marketing.

We may have to agree to disagree. Not on anything very substantial, though. I just think comparing apples to apples is very hard and trying to quantify the difference is even harder. I don't doubt it's more aggressive, but I see more similarities than differences.

Adding regular atrac to open diffs is a big step up in capability. Bigger than the subsequent improvement in atrac and big enough to qualify it for most applications. That is the basis for my statement that it works well.

 

[Thai]

Adding regular atrac to open diffs is a big step up in capability. Bigger than the subsequent improvement in atrac and big enough to qualify it for most applications. That is the basis for my statement that it works well.

I completely agree. No argument from me. Good point(s).

 

[Glock_19]

Getting back to the OP, the terrain listed was gravel, sand, and occasional snow. I highly doubt unless you're explicitly wheeling you'll even get out of 4-HI. You definitely do not need a rear locker. I can't even remember the last time I locked my center diff.

 

[Clone of the Mean]

For years and years (before I got a locker) when I was in a bind I would apply the brake with my left foot and use my right for the gas. You put equal pressure on the axles and kind of fool the diff into thinking everything is OK. Not foolproof, but pretty effective.