Is TRAC as good as a locker?

Was following a '12 Taco over some uneven humpties, and he high sided his right rear. The tire spun to a complete stop in less than a quarter turn, in about a half a second, and all power was diverted to the grounded wheel. Nice...very nice.

But that begs he question...is TRAC (computer controlled wheel braking) as good as a locking diff? I mean, lockers can be hard on drive lines, and cause steering issues. Seems to me our TRAC is actually better than a locker. Opinions?

 

Only a small percentage gets transferred.

Not anywhere near as good as a locker, but it does help.

 

So to start with, TRAC is the system that is engaged all the time. ATRAC is essentially your 4 wheel drive version.

Depends on the use though if you ask me...

On pavement: TRAC is what is used and it the best for pavement. Using a locker will RUIN your drive train. Just the same if you were to engage 4wd on the pavement. (unless its raining and your tires can slip a little bit) If you want to go in a straight line and never turn, then a locker is fine, but if you intend on turning at all do NOT turn on your locker.

Off-road: Lockers are AMAZING to use for a hill climb if you're gonna flex out. BUT I would turn my locker off after a hill climb because of how hard it can be on the drive line if used excessively. ATRAC is on 24/7 in 4wd UNLESS the driver turns it off (lil button) and it will help you with those small little pucker moments. There are times where ATRAC just doesn't do the job for me and I have to turn on my locker. But ATRAC is pretty freaking awesome. I can't think of a single time (man I want Atrac turned off for this section)

I do turn TRAC/VSC off when i'm doing donuts on icy parking lots though...

 

The high side wheel was completely stopped.

 

He must've not been on a very steep climb/ been light on the gas. Cause it's not too hard to throttle through the ATRAC braking.

 

I should have videoed it...I was behind him on a class 2 trail, low speed, and he crested a small but sharp hill sort of off kilter, but leading into another. lifting his right wheel completely airborne, and within a quarter turn and a half second ATRAC (thanks for the correction) had completely braked the lifted wheel, sending all the power to the planted wheel and off he went.

 

Haven't owned personally anything with A-TRAC but it's pretty amazing when you see it in person. I don't know that it's as good as a locker when you lift a wheel completely but I also don't feel it's a 1-for-1 comparison. If I had the choice of one it would be a locker, though. Doesn't take any wheel slip for the controller to engage it and doesn't require the driver to do anything special. A-TRAC seems to work best when you're steady on the throttle and travel at a constant speed.

I don't feel lockers are hard on drivetrains and probably the opposite if for no other reason it allows you to walk stuff more controlled rather than needing so much skinny pedal all the time. I actually broke fewer front CV axles on my old truck with a front ARB because of that I think.

 

What?

Lockers do not ruin your drivetrain in any way. You can leave a locker locked in on pavement for forever and you’re only going to wear out tires quicker. Off road they typically reduce breakage because you don’t need momentum and all the bouncing from diffing out. Locker (lunchbox or selectable) wins every single time over atrac.

 

the thing people need to realize here is there are a few different terms getting thrown around that mean different things.

TRAC (auto LSD) - this is standard on all 09+ trucks, a simulated LSD that uses brakes to transfer power to the non spinning wheel.

ATRAC - ONLY found on 09+ TRD OR 4x4's. ATRAC can ONLY be enabled in 4lo (with locker its active to 5mph, without locker there is no speed limit) ATRAC does the same thing as TRAC, but MUUUUUUUUUUUUUCH more aggressively and efficiently thanks to the electric boosted master cylinder / 4 channel abs all in one unit found on these trucks only.

Atrac does a damn good job, i have been impressed with it. I have been "stuck" unable to get over an obstacle without being a dick to the truck without it active and rear locked (so spinning the 2 rear tires and a front). Hit the atrac switch and the thing chomps forward using the grip of the one non spinning tire up front.

ATRAC is no substitute for a locker, but its the closest thing you can get to one without actually having one. TRAC / Auto LSD found on non 09+ TRD OR 4x4's does decent, but its about half as effective as ATRAC.

A locker is definietly hard on the drivetrain in high grip situations, it binds the rear axle up quite a bit. That stated, if used right, it will be easier on your drivetrain as you dont have to spin a bunch of tires which breaks things.

Also.... a locker in 2wd makes for great doughnuts.

 

In an open diff the power is always 50/50. TRAC braking one side does not transfer more power to the other wheel, there is always equal power to each wheel.

 

uh no. An open diff, power takes the path of least resistance. Hence why if you lift one tire in the air you are going no where. Only a locker / spool does a 50/50 split all the time.

 

So you're saying if I lock my center diff and do several turns, my drive line is going to be 100% fine? Not trying to argue, I'm genuinely curious. That was what I was taught when I was younger, that locking diffs together is harder on the drive line when turning because of the extra stress caused by the resistance of the longer turning radius (whether it be front to back, or side to side)

 

Exactly what I was about to type up lol

 

It will buck and chirp the tires some but it won’t hurt it. Toyota t-cases and axles are stout. I wouldnt hammer on it at full lock with the center locked but parking lot speeds are fine. Rear locker being enganged will just make the inside rear tire chirp too

 

That's correct, an open diff will see all the torque on the wheel in air and none on the wheel on the ground. That's why do you don't go anywhere, there's no torque on the wheel with more friction. A locked diff guarantees you have 50/50, both wheels are locked together so they both spin at exactly the same velocity.

A-TRAC is functionally the same as touching the brakes with an open diff or using a limited slip, which slows the wheel in the air and splits the torque a little bit. A-TRAC works better because the system can apply a single brake so the stuck wheel doesn't lose anything like it would if you touched the brakes lightly (this was the age old trick to driving stock trucks).

A-TRAC is better than a locker in the sense that by applying the brakes on one wheel the other can see more than 50% of the torque in theory, although in practice this isn't really possible because there is a limit to how much force a single brake can tolerate (the wheel not pushing the truck forward is just generating heat). I suspect Toyota isn't using that much braking to prevent loss of torque in the stuck wheel, so a locker is better than A-TRAC in the real world. But as I've mentioned, A-TRAC I've seen in action is pretty effective and operating on both axles is a major advantage over a rear-only locker.

 

It all depends on the situation. Last winter when we had 3 feet of snow on our streets i drove around my block twice, once 4wd regular, once 4wd rear locked (not 4wd low). Locked 4wd was way worse (spinning tires) than 4wd with the auto LSD. I have the "anytime locker mod" on a 2015 DCSB OR. I drove a lunch box locked vehicle for years as a daily driver in non-snow country and loved it FWIW.

 

Now we are splitting hairs, but this is a good point. A locked diff is never the best option in an on road situation. That's why we have VSC/ TRAC. Locked differentials are for off road situations where traction is minimal and you want to make sure both wheels on the axle have power.

The OP was talking off road situations. TRAC and ATRAC are not as good as a locked diff in an off road, low traction/ extreme terrain, situation.

 

I'm thinking a muddy trail would be similar situation

 

Is there any way to add ATRAC to an SR5 4x4?

 

I'm gonna be the contrarian here. On my '09 I did the 4lo Trac mod and thought it was the coolest thing I had ever seen in the snow, and it was. Not so good on dry ground and rocks. When I decided to move to a newer truck, based on my experience with the 4Lo Trac I assumed that ATRAC would be that much better and sought out the TRD OR to get it. After wheeling it hard for a year I found myself stuck in a number of situations I thought should not be. Since I had the TRD OR it had the rear diff locker and I decided to add the Eaton/Harrop front elocker as well. I have compared both many times in the same spot while stuck with ATRAC and then activating the lockers to get unstuck. I rarely use ATRAC anymore.