mrtifftiff
New member
How does the locking center dif interact with either a front or rear locker? Does the center dif need to be locked or unlocked when operating a front or rear or both?
Front/Rear lockers - LE
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BigredTEX
New member
Locking the center dif is no different than switching a normal, part time 4WD system into either 4Hi or 4Lo. The TE, the only model with a factory locker, won't let you engage the locker unless you are in 4Lo, but it would work the same if it was possible to use it in 4Hi or even in 2WD if you removed the interlock.
The center dif mechanically locks the front and rear axles together when locked, allowing no differentiation between then. A locking dif, either front or rear, locks the left and right axle together. You could lock the front, rear, or both without locking the center dif. It would still split the torque 40/60 (or whatever the factory setting is) between the front and rear axle.
The center dif mechanically locks the front and rear axles together when locked, allowing no differentiation between then. A locking dif, either front or rear, locks the left and right axle together. You could lock the front, rear, or both without locking the center dif. It would still split the torque 40/60 (or whatever the factory setting is) between the front and rear axle.
bimrunner
New member
You would lock the center before ever needing the rear or front. The order goes, center locked for keeping the power going to both front and rear for loose rock, dirt, sand... you only engage the rear locker when you need to make sure your rear wheels turning for more challenging technical parts or fun drift driving in the snow! The front locker is engaged when the other two aren't enough to get trough very difficult portions. Once I'm through it, I unlock at least the front depending on the situation. However, the lockers can be engaged at any point. Just don't do that. The order should always be... center locked, if not enough, lock the rear... if not enough, lock the front too. Unlock the diffs when you don't need them.
It is pretty easy if you think about it.
When you lock a differential, both output shafts turn at the same speed. Therefore, when you lock the center diff, both the front and rear driveshafts turn at the same speed.
When you lock the rear diff, both the left and right rear halfshafts turn at the same speed.
Same for the front diff.
I believe the typical procedure is to first lock the center diff, then the rear diff if needed, and finally the front diff. Once you start lock diffs, it becomes hard to turn.
When you lock a differential, both output shafts turn at the same speed. Therefore, when you lock the center diff, both the front and rear driveshafts turn at the same speed.
When you lock the rear diff, both the left and right rear halfshafts turn at the same speed.
Same for the front diff.
I believe the typical procedure is to first lock the center diff, then the rear diff if needed, and finally the front diff. Once you start lock diffs, it becomes hard to turn.
phillyd2
Senior Member
Assuming you are talking about a Limited with aftermarket ARB air lockers? If so, it's independent of OEM systems, including ATRAC. The other guys are talking about the Trail Edition with factory electric rear lockers.
That said, common sense comes into play on when to engage the air lockers. I can't think of why you would want to lock up while not already be in 4L. If going with both front and rear it should be wired where you can't lock the fronts unless the rears are already locked. If only picking one, lock the rears which should handle most of the common situations. Locking the front should only be the very last resort since it really does change how the truck steers, and not for the better.
That said, common sense comes into play on when to engage the air lockers. I can't think of why you would want to lock up while not already be in 4L. If going with both front and rear it should be wired where you can't lock the fronts unless the rears are already locked. If only picking one, lock the rears which should handle most of the common situations. Locking the front should only be the very last resort since it really does change how the truck steers, and not for the better.
mrtifftiff
New member
Thanks for the clarification. I was unsure if there were any mechanical reasons why one would not want to have all three or any combination of the two activated at once. Don't see myself seriously needing a front anytime soon but I can hopefully add a rear locker in the not too distant future. Thanks again!
wfo9
New member
One thing I've been wondering about with a single air locker is this.
If you were in 4wd Lo and had a rear air locker, what would happen if you tried to engage ATRAC. Seems like this would be non optimal as the system would be trying to limit wheel spin on a locked diff (just heating the brakes up and stressing the drive-train for no good reason).
I thought I read somewhere that the trail edition only allows the e-locker and A-Track to both be on below 4mph. If that is the case it might also be performing a-track front and rear at the same time. Otherwise, I'm not sure why it would be speed limited like that.
Ideally, you would want rear diff locked and atrac active in the front only?
Also, if you spend the money on a rear air locker, you are 75% of the way (in terms of cost) to adding a front. Just seems logical to do both if your doing air lockers. The smooth controlled power of fully locked front and rear seems to really make a difference in the potential for on-trail damage compared to the lurching a-trac. The a-trac can get you through a lot but it is not always graceful. Maybe the locked rear with no a-track up front would be enough for 99%.
If you were in 4wd Lo and had a rear air locker, what would happen if you tried to engage ATRAC. Seems like this would be non optimal as the system would be trying to limit wheel spin on a locked diff (just heating the brakes up and stressing the drive-train for no good reason).
I thought I read somewhere that the trail edition only allows the e-locker and A-Track to both be on below 4mph. If that is the case it might also be performing a-track front and rear at the same time. Otherwise, I'm not sure why it would be speed limited like that.
Ideally, you would want rear diff locked and atrac active in the front only?
Also, if you spend the money on a rear air locker, you are 75% of the way (in terms of cost) to adding a front. Just seems logical to do both if your doing air lockers. The smooth controlled power of fully locked front and rear seems to really make a difference in the potential for on-trail damage compared to the lurching a-trac. The a-trac can get you through a lot but it is not always graceful. Maybe the locked rear with no a-track up front would be enough for 99%.
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jbstrd
New member
Correct me if I am wrong, but if you have any axle (front, rear, or both) locked, then A-Trac will never kick in since it detects wheel slippage between the left and right wheels on the same axle. So, with the locker engaged, there will never be a difference in slippage between the left and right wheels.
If just one axle is locked (the rear for example), then the front will engage A-Trac if it senses one front wheel slipping.
Intruder
New member
Exactly.
Centre diff locked only - ATRAC can kick in on both front and rear wheels
Centre diff + rear diff locked - ATRAC can kick in on front wheels
Centre diff + front diff locked - ATRAC can kick in on rear wheels
Centre diff + front and rear diff locked - ATRAC should not kick in
harper7
Senior Member
That's the way I understand it too,if ATRAC senses a wheel slipping compared to the opposite wheel it applies brakes to the slipping wheel and switches torque over to the opposite wheel on that axle.If your rear locker is on, you won't have a slipping wheel compared to the other side and thus ATRAC will never activate for that axle.
The computer is comparing the two wheel speeds with the ABS sensors and they will be the same when locked just like you are going down the trail with no slippage and thus no activating/heating of brakes . The front and rear axles activate separately with ATRAC so you still have ATRAC in the front even when the rear is locked as I can attest to with the ARB air lockers.
As far as if you have the rear locker and that you are 75% there. I can tell you the rear locker can be installed in about an hour or two as the 3rd member is really easy to pull on these and can be done by one person. The front clamshell diff on the other hand is much more labor intensive as the CV axles have to be pulled after you pull the hubs , the front drive shaft bolts are a biatch to get to and not to mention that it's awkward shaped and heavy as hell to get back into place. There's plenty of finesse work on the front too getting things lined back up so you don't screw up the seals for the CV and wheel bearings.
Not sure what your talking about ATRAC not being graceful ,on mine at least, it's very graceful and you can barely tell it's working and a very, very good system. Maybe your talking about HAC,DAC and crawl control that are all weird sounds and jerking ,braking and not graceful. TRAC and VSC ,which are on by default,when your are in 2 and 4 HI are a little awkward because it cuts the engine RPM, switches torque between wheels and applies brakes.If you are ever in 4LO and don't have ATRAC on these things don't hardly have any traction and really appeciate ATRAC and I think it should have been ON by default rather then off in 4LO. If you have it on and turn the truck off in 4LO ,it switches it back off and I almost got stuck several times as I got back in and forgot to turn it on. I am going to look into the switch wiring one day and mod it so it's on by default in Low.
Rear lockers aren't really needed unless you know that it's a hard loose climb ,mud or you think think you there's a good chance you'll get stuck so not that often as ATRAC will take you through 99%. Front lockers are for last resort or almost stuck while going slow,easy on the gas and you'd best be going straight or there's a better then even chance you'll break a CV axle if one side suddenly gets all the traction.
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FrontRange4Runner
New member
You might consider getting into some situations where you think that a locker would be needed. Truth be told ATRAC will get you through a lot of stuff. Probably more than you will be comfortable going through at first. The expense of aftermarket air lockers makes it worth wile to figure out if you will actually ever need them. It would be fun to take a poll of all Trail owners, asking who uses their locker and how ofter they do. My guess is that most people rarely, if ever use their locker. The ones that do are most likely the most experienced (and crazy 
) people we have in the 5th gen section. Truth be told, most people are simply not going to take a new $35-40k truck out and get into many situations where a locker is required. Every time I have used my locker, it has been in a situation where I wanted to - because I had one - and was never even close to actually needing it.
) people we have in the 5th gen section. Truth be told, most people are simply not going to take a new $35-40k truck out and get into many situations where a locker is required. Every time I have used my locker, it has been in a situation where I wanted to - because I had one - and was never even close to actually needing it.
phillyd2
Senior Member
I’ve actually talked to ARB about this. The Air Lockers know nothing about ATRAC and ATRAC know nothing about Air Lockers. If the rears are locked ATRAC simply does not engage for the rears because there is no slippage but will for the front, if they are not locked. Two completely independent systems.
And I also agree with Harper (good to see you around, btw!) about ATRAC. Not only is it graceful but it’s very robust and works. Unlike with lockers one needs to push the skinny pedal to create wheel spin to get the most out of the ATRAC system. Here is a completely stock 4R where you can see how ATRAC kicks in when you are not shy about giving it some gas.
<iframe width="640" height="360" src="https://www.youtube.com/embed/7Rlt-Rhythg?feature=player_detailpage" frameborder="0" allowfullscreen></iframe>
I can count on one hand the number of times I’ve used the front lockers but when I did they were priceless. For most people just having the rears locked plus ATRAC will handle almost everything you would ever need. With just ATRAC you will out drive 99% of the vehicles out there.
And I also agree with Harper (good to see you around, btw!) about ATRAC. Not only is it graceful but it’s very robust and works. Unlike with lockers one needs to push the skinny pedal to create wheel spin to get the most out of the ATRAC system. Here is a completely stock 4R where you can see how ATRAC kicks in when you are not shy about giving it some gas.
<iframe width="640" height="360" src="https://www.youtube.com/embed/7Rlt-Rhythg?feature=player_detailpage" frameborder="0" allowfullscreen></iframe>
I can count on one hand the number of times I’ve used the front lockers but when I did they were priceless. For most people just having the rears locked plus ATRAC will handle almost everything you would ever need. With just ATRAC you will out drive 99% of the vehicles out there.
wfo9
New member
This is good info. I did not realize A-trac detected wheel to wheel slippage across the axle. I thought it was trying to limit slippage on any wheel vs vehicle speed, but this explanation makes way more sense.
I'm not down on a-trac at all. It does work great. I just don't like the fact that the throttle control is not 100% smooth with it for slow crawls. You end up going faster and using more throttle than what would be necessary with a locker; leading to more damage on the trail.
As far as my comment about the cost of both vs rear, I was mainly referring to the air system itself. That seems like a significant part of the cost and labor, but I did not realize the front was that much more labor.
I'm not down on a-trac at all. It does work great. I just don't like the fact that the throttle control is not 100% smooth with it for slow crawls. You end up going faster and using more throttle than what would be necessary with a locker; leading to more damage on the trail.
As far as my comment about the cost of both vs rear, I was mainly referring to the air system itself. That seems like a significant part of the cost and labor, but I did not realize the front was that much more labor.
STX4Runner
New member
I don't know if anyone has or not, but I don't think its cost effective as you need a new third member (or at least a modified one) to accommodate the e locker motor, a dashboard switch and ecu I think. Much more reasonable to get the ARB.
wfo9
New member
There is a good video of open diffs vs Atrac vs dual lockers, in this video at about the 1 min mark.
https://www.youtube.com/watch?v=YNFacsKnswM
There is also a part 1:
https://www.youtube.com/watch?v=C2wkW05Pc6c
They're obviously trying to sell lockers, but it is a useful demonstration.
https://www.youtube.com/watch?v=YNFacsKnswM
There is also a part 1:
https://www.youtube.com/watch?v=C2wkW05Pc6c
They're obviously trying to sell lockers, but it is a useful demonstration.
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