How important is locking rear differential?

[jhmoore]

I'm on an overly long and convoluted journey to having a vehicle to take off-road... not for the purpose of off-roading, but for the purpose of photographing places that are hard to get to--mostly in the Southwest United States (I'm in San Diego). Had been looking at a new 4Runner, but am now feeling more like I don't want a car loan and buying something used.

The 4th Generation 4Runners don't appear to have had locking rear differential as an option. I'm not an experienced off-roader, but I've been given lots of advice that this is one of the must-have options. Yet it's not even available for many years in 4Runners.

So... for getting down bad gravel and sometimes bad sand road in the SW United States, and maybe occasional snowy roads in the mountains... not rock-crawling the Rubicon trail, how important is locking rear differential?

Thanks for any advice!

 

[Barry694]

Locking rear Diff

I Spent eight years crawling through the Sierra's in Northern California and got into many rough places. Most of the time in 4HI, If it got to where I could not go anymore I used 4LO and it always got me out. I had locking rears and never had to use it. But it was comforting to know that if I ran across certain situations it would be available. I also pulled a heavy boat out of Lake Oroville each season and by that time the lake had dropped below the end of the ramp and I was in mud, wood chips, bark, and other small garbage. The ramp was close to 45 degrees when that low and I never needed anything but 4LO to get moving and as soon as I was on the solid surface of the ramp I changed over to 4HI and went on up. The ramp can get pretty long at the end of summer with a lot of the water being sent down river for irrigation and drinking water.

 

[chaz]

09 trail edition has rear locker, if you can find one. http://autos.msn.com/research/vip/overview.aspx?year=2009&make=Toyota&model=4Runner

 

[Clemsonfan15]

I don't think it's necessary for your intended use.

However, like chaz said, some of the 2009 models have a locking rear differential.

 

[03_4x4Runner]

A locking rear diff can be added to about any vehicle with companys like ARB. They make lockers for all model 4runners. You may never need one but that one time you do when you are many miles from help and you are by yourself it will be well worth it. Check out the videos of me in the photobucket in this link. http://www.toyota-4runner.org/4th-gen-t4rs/83068-trac-concerns-1st-attempt-video.html A locker would have had no problems here when the atrac was limited.

 

[KCcarguy]

Why not a FJ cruiser?

I'm not sure if FJs appeal to you at all, but rear lockers are much more common on FJ's and there's some pretty decent prices on used ones. They have ATRAC as well. I think you have to get the offroad package, but there are plenty of them out there. The '09 TE 4runner is damn near impossible to find and you'll pay more for it. Good luck and let us know what you go with!

:cheers:

 

[KidVermicious]

I'm on an overly long and convoluted journey to having a vehicle to take off-road... not for the purpose of off-roading, but for the purpose of photographing places that are hard to get to--mostly in the Southwest United States (I'm in San Diego). Had been looking at a new 4Runner, but am now feeling more like I don't want a car loan and buying something used.

The 4th Generation 4Runners don't appear to have had locking rear differential as an option. I'm not an experienced off-roader, but I've been given lots of advice that this is one of the must-have options. Yet it's not even available for many years in 4Runners.

So... for getting down bad gravel and sometimes bad sand road in the SW United States, and maybe occasional snowy roads in the mountains... not rock-crawling the Rubicon trail, how important is locking rear differential?

Thanks for any advice!

Lockers are nice, but it doesn't sound like you'll need one. High clearance and good gears are enough for most "bad" roads, and about any 4WD setup will get you through sand if your tires are decent. Where lockers most often come into play is when you're on trails, and even then it's a burly trail that a stock 4Runner can't handle.

If you change your mind and decide you need one down the road, installing a selectable locker can be as easy as getting an axle from a donor vehicle with the right gears and bolting it on.

 

[fourwd1]

Lockers are not a "must have" for your average wheeler.
But they are nice to have, and can always be added later.

 

[Thai]

Like others, i think that you don't NEED it for your purposes, but it is nice to have...and if your budget allows for it, then i would get it. After getting it (or before), i would read as much about it as possible, including what is the function of such and when to use it.

Personally, when i had my G-wagen, i almost ALWAYS lock my rear end when going off the beaten path. (My G had ATRAC also.) Unlike ATRAC, a locker is "proactive." ATRAC is reactive in the sense that your tires must slip to a certain degree before the system reacts/kicks in. And by that time, you might have lost momentum and traction. ATRAC is always playing "catch up" with traction (or lack of).

IMO, a locker is really NOT to be used AFTER you get stuck. It is to be used BEFORE you approach an obstacle. By locking an axle, you are guaranteeing that both tires on that axle gets power all the time. In this way, the rear axle tires don't have to wait for one of them to slip before the other tire gets power. Full power to both axles...no waiting for power shift...no loss of momentum.

 

[JB.]

So... for getting down bad gravel and sometimes bad sand road in the SW United States, and maybe occasional snowy roads in the mountains... not rock-crawling the Rubicon trail, how important is locking rear differential?

Thanks for any advice!

I've done a ton of what you're referring to (not for photography but exploring, hiking) with stock suspension and no rear locker. On the very rare occasions I've needed more capability, a quality suspension lift would have been of more use than a locker. 4WD with ATRAC works very well.

 

[KCcarguy]

I've done a ton of what you're referring to (not for photography but exploring, hiking) with stock suspension and no rear locker. On the very rare occasions I've needed more capability, a quality suspension lift would have been of more use than a locker. 4WD with ATRAC works very well.

My friend with an FJ says the same thing. He says he uses ATRAC all the time. He has literally never used his e-locker when wheeling.

 

[Thai]

My friend with an FJ says the same thing. He says he uses ATRAC all the time. He has literally never used his e-locker when wheeling.

Remember, A-TRAC on the FJ is a true off-road tool...it can ONLY be used in 4-LO and is very aggressive. ATRAC on the 4runner (4th gen, not named Trail Edition) is a much milder version.

My opinion is different than JB...i prefer having a rear locker + good tires over a lift. I don't like to modify suspension geometry from factory settings for reasons of durability.

 

[fourwd1]

... IMO, a locker is really NOT to be used AFTER you get stuck. It is to be used BEFORE you approach an obstacle...

Well that takes a lot of the fun out of wheeling

If you always engage the locker first, you'll never know what the truck is really capable of doing. You can learn it's limits, then get out of it.

 

[Thai]

Well that takes a lot of the fun out of wheeling

If you always engage the locker first, you'll never know what the truck is really capable of doing. You can learn it's limits, then get out of it.

Haha, that's ok...I have had my share of being stuck...no need to torture myself and my group with my stupidity!!

 

[JB.]

Remember, A-TRAC on the FJ is a true off-road tool...it can ONLY be used in 4-LO and is very aggressive. ATRAC on the 4runner (4th gen, not named Trail Edition) is a much milder version.

My opinion is different than JB...i prefer having a rear locker + good tires over a lift. I don't like to modify suspension geometry from factory settings for reasons of durability.

Just to clarify for the OP, my view is based on more than 5000 miles of almost exactly the kind of wheeling he's referring to. Picking lines down miles of clearance challenged tracks is hugely different from playing on recreational obstacles.

Additionally, I don't believe the difference in atrac aggressiveness between vehicles is as large as you think. Based on how it acts in my truck, there just isn't a huge amount of room for additional aggressiveness without getting to a point where the brakes would be just be virtually clamped to the rotors. Also, in the case of the V8, there's more torque to offset the slowing effect of the pulsing brakes on steep slopes.

 

[Thai]

Additionally, I don't believe the difference in atrac aggressiveness between vehicles is as large as you think. Based on how it acts in my truck, there just isn't a huge amount of room for additional aggressiveness without getting to a point where the brakes would be just be virtually clamped to the rotors. Also, in the case of the V8, there's more torque to offset the slowing effect of the pulsing brakes on steep slopes.

I don't think that V6 4runner lose momentum because the V6 engine does not have torque to overcome the braking action of ATRAC. That is not an issue i don't believe. The fact is that ATRAC lags behind real-time traction...and thus may be late to the party in determining which wheel(s) needs traction. And by virtue of it being late, you lose momentum...which does not have much to do with torque (or lack of).

Again, remember that the A-TRAC in FJ is ONLY used in 4-LO and ONLY at low speeds. It is not used at higher speeds because the aggressive clamping down of the slipping wheel would make it hazardous at higher speeds. There is a reason why it is a 4-Lo tool and not an all-season traction control (like that in most 4th gen 4runners).

 

[KCcarguy]

Remember, A-TRAC on the FJ is a true off-road tool...it can ONLY be used in 4-LO and is very aggressive. ATRAC on the 4runner (4th gen, not named Trail Edition) is a much milder version.

My opinion is different than JB...i prefer having a rear locker + good tires over a lift. I don't like to modify suspension geometry from factory settings for reasons of durability.

Is the 5th gen's ATRAC same as the FJ's?

 

[Thai]

Is the 5th gen's ATRAC same as the FJ's?

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

 

[JB.]

Again, remember that the A-TRAC in FJ is ONLY used in 4-LO and ONLY at low speeds. It is not used at higher speeds because the aggressive clamping down of the slipping wheel would make it hazardous at higher speeds. There is a reason why it is a 4-Lo tool and not an all-season traction control (like that in most 4th gen 4runners).

I don't follow what you're saying here (higher speed, all season?), but the operation has to be similar in low range.

If I put my truck in low range on an ice hill that it has no chance to climb and try to go, the wheels turn slowly with a choppy motion from the brakes. If the FJ atrac is more aggressive, that's great, but there's not room for too much more aggression without stopping the wheels completely.

The 4th gen atrac works well but left room for a little tweaking.

 

[Thai]

I don't follow what you're saying here (higher speed, all season?), but the operation has to be similar in low range.

If I put my truck in low range on an ice hill that it has no chance to climb and try to go, the wheels turn slowly with a choppy motion from the brakes. If the FJ atrac is more aggressive, that's great, but there's not room for too much more aggression without stopping the wheels completely.

The 4th gen atrac works well but left room for a little tweaking.

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!