ATRAC + Locker(s)

ErikM

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How does ATRAC work when a rear and/or front locker is engaged?

I have ATRAC, locking center diff and no rear or front lockers currently. Right now, slow and steady on the throttle, ATRAC kicks in and up the hill we go (also have center diff locked btw).

If, err, when I get a rear locker (or front or both), what changes where ATRAC is concerned? Is ATRAC thrown out with the dishwater?

Thanks,
 

AlpineAccess

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Rear locker with A-trac in the front is how a lot of the TRD Offroad 4x4s are setup from Toyota. I can't see a scenario where A-trac would be compatible with a locked axle as the locker is sending power to both wheels regardless of traction available. A-trac brakes the wheel that is spinning which diverts more power to the other wheel and then uses some tech wizardry to modulate the braking and spinning. It is amazing, especially on loose up-hill rock/dirt surfaces in my experience.

On my FJ and Tacoma, my understanding was that with the locker on A-trac was only active on the front axle. I'm not familiar how it would work with aftermarket lockers. I know there are scenarios where front and rear lockers combined are amazing, but for 95% of the offroading I have done, A-Trac and a rear locker were the best combination. My 100 series doesn't have A-trac or a front locker and I notice it more than I thought I would.
 
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Inukshuk

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Admittedly I do not have first hand experience (my truck didn't get TRAC/A-TRAC but I do have a factory locker).
but stayed at a Holiday Inn Express FWIW
On my FJ and Tacoma, my understanding was that with the locker on A-trac was only active on the front axle.
^^^ THIS is the answer. A-trac remains active on the front axle. Its a great combo because you get traction enhancement with minimal steering impairment.
 

Shuksan

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I am getting ready to put a locked rear axle in my 2000 LC which has ATRAC. My understanding is like what Dave and Dan are saying. When I lock the rear, then the ATRAC will have no reason to activate on the rear. However it will still function as normal on the front.
 

AimCOTaco

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I agree with @Shuksan and @DaveInDenver and I say they are compatible because a locked axle won't trigger A-TRAC as it won't sense any differential rotation when it is locked. When the locker is off, the system could detect any slip and actuate.. but won't be at odds with an open locker.
 

Romer

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I have front and rear ATRAC on my cruiser and Front a rear Lockers. 100 series and 200 series have them as well as some 4runners

One off road technique is power braking, where you put your foot on the brake, rev to 1000 or 2000 RPM depending on the situation and slightly release the brake to have easy and controlled forward momentum. If the brake is used, the ATRAC is disengaged

Playing around I have noticed that the ATRAC does well, but not as well as a locked axle for traction

I do think ATRAC does a pretty good job and if had to do it over again, would only install a rear locker. A rear locker covers 90% of scenarios in any case. The ATRAC on the front can help in some situations as well. The exception to this is some year 100 series that have a weaker pinion and the locker provides strength even when not in use
 

Inukshuk

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My 2006 100 has ARB lockers. I'll try to find a place this weekend to test what @AimCOTaco said and we all believe to be true.
 

nakman

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Depending on the terrain, you may find you're using the ATRAC more than you think as so often it takes a little while for things to line up and the locker to engage. So you see the big scary bumpy thing, push the locker button, drive up the obstacle, then look down and the light is still flashing... happens a lot in an 80 series particularly in back where the splines are bigger. ARB's engage a little quicker.

@ErikM I would recommend holding off on a locker as long as possible.. you already discovered that just a litttle throttle and line selection is getting you through a bunch of stuff, as you gain experience you'll just get better at this. Good tires, proper pressure, right amount of momentum, all stuff to master. that said, it's fun to aim for the big stuff also, and lockers are cool. :beer:
 

MountainGoat

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I don't know about the 4th gen 4Runners, but in our 2000 100 Series I almost always forget to lock the center diff when I put it in low range. I am used to the 80 and our 1999 100 Series where it locked automatically when you put it in low range.

I have "failed" to get up obstacles and taken a strap only to notice later that I never locked the CDL. Doh!

Otherwise I have been pleasantly surprised by how well ATRAC works. :)
 

ErikM

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Thank you all for the your thoughts and comments. I am pleasantly surprised at how well ATRAC worked last weekend.

Re lockers, I have a quote from Bullhide for front and rear air lockers, plus the "big" compressor and a 4way tire inflation system. Bit pricey for everything, obv, so I'm thinking just the rear, compressor and inflation system. Total just over $4k.

A much as I'd like to get both front and rear I, currently, think I'll hold off on the front but check with me in a week because I might change my mind. Part of the thinking is to get it all done now and focus on the "little things" over the next year or two.

Unfortunately, those "little things" come with a bigger-than-little price tag 😭.
 

DaveInDenver

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Are you planning to change gear ratios at the same time? That would be the only strong argument for really needing to do front and rear lockers at the same time.

You must be in Larimer County? I bought some stuff at Bullhide, nice guys and never had a lick of trouble with them but never had them do labor. I'd be maybe a little worried that they are Jeep guys, though. Just my $0.02 but you might think about throwing your hard earned cash at guys like Slee setting up diffs.
 

3rdGen4R

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Are you planning to change gear ratios at the same time? That would be the only strong argument for really needing to do front and rear lockers at the same time.

You must be in Larimer County? I bought some stuff at Bullhide, nice guys and never had a lick of trouble with them but never had them do labor. I'd be maybe a little worried that they are Jeep guys, though. Just my $0.02 but you might think about throwing your hard earned cash at guys like Slee setting up diffs.
Dave is correct. Really the issue becomes what tires are you running? Also how much trail time do you have on the system you have right now. I think you’d be pleasantly surprised on just how much you can do with the setup you have. And maybe waiting to do this big job in the future will be easier to spend a little more money on regearing at the same time.
 

Romer

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Erik,
I agree on waiting on the front. I think the rear will get you everything you want. Do get the big dual ARB compressor. It is great at airing up tires

Since you wont be doing the front, gearing really isnt an issue to considerer UNLESS as said above you want to run really big tires. If you do regear you have to work on both diffs and may want to add a locker at that time. decisions decisions

Ken
 

ErikM

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@DaveInDenver We live in Firestone (Weld country) so Bullhide is 30min-ish north of us.

That's an interesting point, Dave, re Jeep guys. Never crossed my mind. They are going to install a 3" lift, upper and lower control arms, rear suspension (200lbs-plus coil springs) and skid plate next month. We're getting some 285/70R17 KO2 6ply tires at the same time. Any concerns about Jeep folks doing this for us?

@3rdGen4R we've been doing this all of 2months now. A lot of it is thinking what we'll eventually need, real and/or imagined. Knowing what I now know about ATRAC I can see the benefit of using just that and seeing where we can and can't go. However, I really don't like the idea of going someplace to find out that I can't get past an obstacle cause ATRAC just ain't cutting it. In my mind's eye "if only I had a locker I'd be unstoppable etc, etc, etc."

I asked at the Newb run, re: needing to re-gear with the kit we were adding, etc, and I thought the consensus was no, not at that tire size. If we got the rear locker, would that change things? What does a front locker have to do with needing to re-gear?

@Romer Agreed, decisions decisions. I have decided to pass on the front locker for now. So, 1 less decision to make is a good thing, right? :)

I really do appreciate everybody's feedback. I don't want to drop a lot of cash if I don't need to.
 

DaveInDenver

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@DaveInDenver We live in Firestone (Weld country) so Bullhide is 30min-ish north of us.

That's an interesting point, Dave, re Jeep guys. Never crossed my mind. They are going to install a 3" lift, upper and lower control arms, rear suspension (200lbs-plus coil springs) and skid plate next month. We're getting some 285/70R17 KO2 6ply tires at the same time. Any concerns about Jeep folks doing this for us?
A good mechanic is a good mechanic, so "concern" isn't really the right way to put it. It's just that if a shop doesn't work on Toyotas (or whatever brand) a lot they won't know the gotchas to watch out for. One part about suspension lifts that I feel benefits from prior experience is the alignment done at the end.
I asked at the Newb run, re: needing to re-gear with the kit we were adding, etc, and I thought the consensus was no, not at that tire size. If we got the rear locker, would that change things? What does a front locker have to do with needing to re-gear?
If you don't change ratios then you don't have to touch the front diff at all. If you're putting in new front gears (both front and rear diff ratios have to be the same, not sure if you know that) then you might consider doing a locker at the same time to save paying labor again later. It's only the cost of the locker at that point, you're paying the same labor to set up a new ring & pinion either way.
@3rdGen4R we've been doing this all of 2months now. A lot of it is thinking what we'll eventually need, real and/or imagined. Knowing what I now know about ATRAC I can see the benefit of using just that and seeing where we can and can't go. However, I really don't like the idea of going someplace to find out that I can't get past an obstacle cause ATRAC just ain't cutting it. In my mind's eye "if only I had a locker I'd be unstoppable etc, etc, etc."
Many old timers started with completely open diff trucks without any traction aids, so A-TRAC puts you ahead of the game already. There won't be a lot of trails where you will have trouble, really. And if you do find hard spots trying stock just helps you learn line selection, momentum, etc. Makes you a better driver. If you're with club members worst case is you get a pull through a tough spot with a strap. As long as there's been 4WD trucks and clubs the first impulse has always been to max out the credit cards putting on everything but it's better to get experience first, see what you really need. I'd suggest sliders (just as insurance) and decent tires and go on some runs first, but that's just me.
 
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Inukshuk

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@ErikM I'd go full OCD when it comes to a lift. I have been wheeling 20 years and 240,000 miles in that 80 you saw Saturday with a simple bolt-on Old Man Emu (OME) 2" lift and OME shocks. I can run all but the absolute hardest Moab trails and still cruise the speed limit to Baja and back no problem.

I have factory lockers, I like lockers, I rarely "need" them.

I don't know that shop, but the first modification should be the nut behind the wheel (the driver). I run about the same tire size as you mention. I cannot speak to the particulars of lifting a 4Runner but my resources for a 4Runne would be Toytec and Cruiser Outfitters - people who know quirks. Many jeep guys just bolt crap on and hope it works. If not, they bolt on more. Maybe your shop is an expert, I don't know. 3" is a lot of lift.
 

ErikM

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You guys have some really good points. Talking with the Mrs, we're thinking what Dave said makes a lot of sense, that is hold off on either locker and ride it out for a few months and see what's what.

If we stick with the 3" lift, 33" tires, etc, realistically, and looking at the FunTreks books for Colo, where do you think we could go with our 4R (driver skill notwithstanding)? I would guess all the greens and most if not all of the blues and maybe some reds? All green and all blue and many reds?

FT Northern Trails:
FT - Northern CO.jpg


Southern Trails:
FT - Southern CO.jpg


I would like to think I could get to a point as an experienced driver with a capable rig where I would be able to do Hell's Revenge and the like so I am 99.9999% positive both lockers will eventually happen but maybe now is not the time.

Would it make sense to get the compressor so when, not if, we eventually get lockers we'd have that already done? Plus the air-up factor would be swell.

Thanks,
 

Inukshuk

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Your truck is capable for Hell's Revenge as it is set up today. Reading that trail list brings up so many great memories and the desire to complete the list!

I have not seen you mention sliders. I forget - do you have them? That is often the first recommended mod. Tires & sliders. Sure it is fun to have a modified rig that you can point and shoot, drive anywhere, not a worry. But it is also fun to learn how to pick the best lines and drive.

A compressor to air up is worth it now. The small ARB locker compressor is not so great for airing up. I find the ARB twin worth the cost. Buy once, cry once. I owned three compressors in 23 years of 4-wheeling. The first was a now-discontinued "Quick Air". Was expensive for 1998 dollars and I ran it 14 years. The second was $50 at Pep Boys and lasted two fills. (to be fair, some of the current less expensive compressors work really well) I have had the ARB twin now since 2013 and it gets used a lot.
 

MountainGoat

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My experience is that Wells has a tendency to be a bit over dramatic in his trail ratings. I have personally done about half of his "difficult" trails in either a stock 3rd Gen 4Runner or a stock 100 series with only tires as upgrades. Granted the Runner has a factory rear locker and the 100 has ATRAC. With those trucks I often wish I had some sliders, even if just for the peace of mind.

I ran my 80 with just tires and sliders for years before I ponied up for a mild lift.

With tires, a mild lift and sliders your truck would be capable of every trail on those lists except about 1/3 of the most difficult ones. A key point will be having someone else with you to help out when you make a bonehead mistake as a driver (which you will because that is how you learn). And honestly your truck could do all but a few of the trails on both lists, but you would have to disregard mechanical sympathy. That's a bad idea.

:)

I think your approach is correct. Make your decision on what to do next when you figure out what you need/want based on experience. That will also make you appreciate future mods all the more. :thumb:
 

DaveInDenver

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I think most people come to the same conclusion as Dan about Charles Wells' book and difficulty. Relative to a stock Toyota black (easy) probably doesn't need 4wd or low range, blue is a fun drive and red (difficult) usually described an actual 4WD trail that requires concentration but is almost always doable.

In any given book there might be a couple of red trails that are genuinely hard, like a Holy Cross or something like that. When you read the description he'll usually give you a clue and you can research it more. But even if not if you hit a spot that worries you just turn around or look for a bypass or detour.

Personally I'm cautious generally but in a group I'm much more likely to push the limits and, honestly, you are usually going to be fine. Which is a self-reinforcing training loop. The next time you're out alone you'll be more capable of doing something harder alone without issues or judging when you need to give up. You improve and get to know your truck better.

There is a scale here though. An experienced driver can probably get a RAV4 through something a newbie might struggle with even with a locker. Experience! But that's why you're part of this club. Go on runs, people will show and teach you stuff. You learn a lot watching someone else and listening to their spotting.

Regarding difficult. For example, one famous club first gen mini truck did just fine on one of the red trails at the higher end of his scale - Wheeler Lake. Just 30" BFG MTs. No bumpers, sliders, lockers, tons of lift and armor. Just an adventurous lugnut behind the wheel of a Toyota truck. There is a point where you need a bit more at the very end, but that's where you roll up the windows, park and walk the last few hundred yards to the lake. It's not a given you have'ta drive every foot of every trail in Colorado to enjoy it.

DSC00936_mid.jpg
 
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