How does the A-TRAC stack up?

I'm trying to solicit opinions from those with experience. I know how it's *supposed* to work. Theoretically it's totally kick-ass. But in real-world usage, how does it fare?

I have an '09 OR edition with it, but honestly I'm just sort of getting into this stuff, and am curious about what I have and what I should watch out for. I've never run with a full-locker diff before, and this truck has it in the rear which is cool, and even cooler the '09's can run with the locker engaged AND A-TRAC working up front. That is, so long as A-TRAC works worth a damn...

I've found myself stuck in some icky situations in the last couple of months. I don't have much going on, the truck is mostly stock, put on some Cooper Discoverer S/T's is all. Found myself stuck along a mucky (I mean MUCKY too) river bank not once, but TWICE in a two-month span, latest was today .

What are the pros/cons of A-TRAC? Where does it work best? Where is it so bad that I should just turn it off? How does it stack up to other options? ARE there other options for the Tacomas?

Anyone else ridden in them and care to share their expert opinion? I don't know anyone personally that has the faintest idea, so I sort of feel like I'm treading new ground here by myself, and would sort of like to sponge information of the more-informed masses

 

It will not save you if you're bogging. If there's traction to be had it'll help you. It's badass in the rocks and loose shit. It limits wheel slip so your tires stay gripped. I wheel in 4Lo with ATRAC on all day and only kick on the rear locker for mud. I've lifted tires and rolled through rocky sections that jeeps on 35" tires got pulled through.

There's a couple ATRAC threads. Try finding'em. It's a night and day difference from an open diff and I'd say in some ways better than a locker since you have an open diff for tight turns.

 

Yeah I've spent some time trying to 'think' about the logical applications of it, and technically it SEEMS superior to even a locked diff, in that locked diffs apply 50% torque to each wheel 100% of the time whereas A-TRAC theoretically 'locks' the spinning wheel and diverts 100% of the torque to the planted wheel. Of course, theory & application aren't always the same, hence the post... I mean, further thought and you realize that the truck only knows a wheel is slipping if it's actively slipping, so how long will it lock the free wheel for? say it kicks on at 1-sec. intervals, and the wheel is up in the air or otherwhise without traction for a length of 5 seconds? Then every other second, you're losing momentum because A-TRAC releases the wheel to test if it's spinning, you lose forward momentum during this as the other planted wheel loses torque application, and THEN A-TRAC kicks in again... At this point I'm just guessing though, because I'm not well-versed in the more technical points, lol, hence the post...

I tried searching for "A-TRAC" & "ATRAC" both on the site, came up with only three threads, and none of those three really laid it out well, I felt, which is why I posted THIS thread. The only one that was of half-value was one about YOU (Luni) in a mud pit on stock rugged trails but If I'm doing it wrong, could you direct me to some good threads on the debate? I'd be interested to read & learn, for sure.

PS: Yeah I didn't reallly blame A-TRAC for the mud issue, it's just that it was kicking on during the fiasco and it got me thinking about it; seems to me that once my A/T's effectively became slicks I was forked anyway. At the time I knew the Rugged Trails were carp, but I didn't feel I really "needed" to go to M/T's so went with Cooper Discoverer S/T A/T's. This mud though, it's not just mud. I can't quite explain it right now, it's too early in the morning. But suffice to say that once you find it, it's well, well too late.

My Bad

 

luni crawled up what my lsd non A-track had to back off of and get momentum

 

it really does work... but as stated before it only works IF there is traction to be had. if your in the rocks or really dry conditions it will become your best friend.... however in the mud leave it turned OFF!! i dont personally have it on my truck however i wheel with alot of FJ's that have it and it ceases to amaze me what it can do!

 

Silver: Yeah those videos are all pretty cool. But they just touch on it, no real technical details (for instance, how long does A-TRAC lock up a wheel, under what cicrumstances, etc). And I wish that they'd have made some of those links available from their Tacoma pages, seeing as how the 2009's have the same goodies. Would have made my research easier last year!

But see, as far as mud is concerned, I haven't yet come to a conclusive "off" or "on" decision. I can't see where it's any real harm per se, though yeah it makes perfect sense that rocky, hilly, even loose & slippery stuff (at least under one tire) would really benefit most from A-TRAC...

But in mud, is it really detrimental? I mean it's not braking the engine like VSC, it's braking the disproportionately spinning wheel and diverting all applied torque to the one with "more" traction (though yes I realize that in mud, "more traction" can be a fairy tale). So you're not really losing momentum, it would seem worst-case that you're simply alternating which wheel is pulling you forward – or, in my case, deeper & closer to the river

If "DEFINITELY OFF!" for the mud, why is that? Sorry to be a pain, but I like to KNOW! I like to try and understand all the minute technical reasons for things, even if they're sometimes beyond me, though this shouldn't be.

'Splain, Lucy

So, uh, at what point did you cease to be amazed haha sorry it stood up and asked for it. No hard feelings – between you & Silverback, those are the trucks I plan to become (except w/ A-TRAC & E-Locker, obviously...)

 

ATRAC runs off 2 wheel sensors, VSC/TRAC runs off one. It responds quick. As soon as the contact patch has been sheered the wheel brakes to regain traction by detecting the difference in wheel speed from the opposite wheel since obviously the wheel with less traction will be spinning faster. If the tire is in the air the braking will redirect some power to the planted wheel, if it just muscled the tire loose it resets the contact patch and braking keeps the tire from torquing loose again.

It is possible to throttle through ATRAC, the brakes can only stop so much. I've found it works best at 2,000 RPMS. In 4Lo that's plenty of power to put it up 30*+ embanks and rocks without defeating ATRAC. If you floor it ATRAC will try to engage, the wheel won't slow down, you won't regain traction and the wheel will slip until you ease off the gas.

Exactly. If the mud hole is hardbottom it will help you maintain forward momentum and if there's a ledge or a rut it will provide power to the wheels with traction to get you up and over instead of spinning tires and digging in.

http://www.toyota120.com/forum/showthread.php?t=25

I did most of my homework with those guys. The 4Runner/Prado crowd has had ATRAC for years. Some great videos there too.

 

thanks Luni. I'll read through that thing. I've already come up against conflicting information so I'll keep reading what I can. I've read, and perhaps improperly assumed true, that it can theoretically divert nearly ALL applied torque to the planted wheel, but I've since read otherwise this day, some stating that at best it can offer about a 50/50 split, and in real-world it's some measure less than that, basically putting its usefulness at about the level of a decent LSD...

More reading is in order, obviously. BUt hey with a rear locker and A-TRAC up front I guess I'm about as well-equipped as it gets.

Thanks for the info!

 

I like to see someone lift a tire with a LSD. Actually, I have. Dark Knight wheels a TRD Sport with mechanical LSD. I was right behind him and as soon as his back right tire lifted all his forward momentum was gone. Watch those videos. It'll make you a believer. I hunt out the off-camber lines where I can lift a tire now.

If I go wheeling and don't put a tire in the air and make ATRAC go off it was a sad day. When we went to URE I was chasing lines that would float a tire all day for that exact reason. Once you can roll those kinds of obstacles with confidence it's a whole new ball game. It also opens up a lot of new lines. You can stay off the big rocks if you can get crossed up with confidence.

 

It works great here in the Colorado mountains... It's taken me places you couldn't go w/o A-Trac or a locker... Lots of places w/ rocks and uneven terrain where only 2 wheels are on the ground...

 

Well I'm glad someone with experience is of that opinion... Most of the people I see saying otherwise seem to be "teching" it out. They dont' know but they're supposing based off of knowledge of some system they think they have (that's proprietary for all I can tell).

Good. MAN! I can't wait to get my lift & M/T's. It's gon' be fun. I figure the M/T's will help with the Mud situations ENORMOUSLY, and A-TRAC & lift will be the icing on the cake for everything else!

 

All you need is skids and sliders

 

the thing about ATRAC and mud is that that the whole way that it functions is to stop one of the tires. it does this so that it can send power to the other tire that has stopped pulling due to "to much traction". now in mud typically you are spinning all four wheels due to a lack of traction so if atrac starts stopping and starting wheel spin again your just slowing the process. when dealing with slick goopy mud its all about the wheel spin. thats why its important to have a tire that is good at self cleaning..

as far as comparing it to an lsd.... well for true offroading the lsd is junk. they wernt designed for offroad use, they were designed to aid with traction on wet slippery roads. in snow they are great but short of that they have no use offroad. i have a sport which came with the lsd rear which was replaced after 1500 miles with an arb.