ATRAC damage, discussion.

[zimm]

heres a good discussion.

it was suggested in another thread that the shock of atrac engage/disengage would damage axles and gears before a locker....

i say poppycock.

first, the atrac works by braking an open diff, which by definition means the tires will see at best HALF the TQ at the tire and rock interface.

second, the stopping and starting, while fast, isnt instantaneous. fast, but not hammer to glass fast.

third, the programming in the abs system cuts ATRAC loooong before enough kinetic energy can build in the system to break anything. ATRAC doesnt engage at high speeds, and when it is engaged, while the stop start is rapid, the tires simply arnt moving fast enough to build enough resonance to snap an axle.

and lastly, i googled ATRAC axle damage, and gear damage, and whatnot, and cant find much there.

now, lockers on the other hand., well, they are the bane of any front birfield/cv off camber, turned, with a tire up. the bigger the wheel, the more powerful the motor, the steeper your gears, the more you have to be concerned about 100% of the forward TQ being applied at an odd angle.

so, while the apparent "grinding" of atrac in action can be disconcerting to the seat of the pants NVH impression, i maintain the system is a "soft" traction control, since it has give, whereas lockers bind all components together causing infrequent tragic consequences, when the rubber earth interface isnt the weakest link.

 

[Scott Brady]

It all depends on the driver and conditions. In a rock crawling situation, I believe A-Trac would cause differential and axle damage before a locker would, particularly if the vehicle is being driven appropriately. A-Trac requires wheel spin to activate. A wheel that is spinning, then suddenly making contact with a high traction surface (like Moab slick rock) is a lot more likely to cause damage then a slowly rotating and locked wheel.

The counterpoint would be A-Trac in a tight turn. Drivers typically do not know the stress a locker can impart in a tight turn, particularly with a CV axle. Overall, lockers driven properly are much more gentle on the truck and terrain than traction control. . .

 

[Ryanmb21]

Two videos done by 4wd action in Australia were the compare ATRAC to diff locks.

http://youtu.be/C2wkW05Pc6c

http://youtu.be/YNFacsKnswM

Here is a thread on toyota120 talking about ATRAC
http://www.toyota120.com/forum/showthread.php?t=244&highlight=atrac
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[David Harris]

It all depends on the driver and conditions. In a rock crawling situation, I believe A-Trac would cause differential and axle damage before a locker would, particularly if the vehicle is being driven appropriately. A-Trac requires wheel spin to activate. A wheel that is spinning, then suddenly making contact with a high traction surface (like Moab slick rock) is a lot more likely to cause damage then a slowly rotating and locked wheel.

The counterpoint would be A-Trac in a tight turn. Drivers typically do not know the stress a locker can impart in a tight turn, particularly with a CV axle. Overall, lockers driven properly are much more gentle on the truck and terrain than traction control. . .

I experienced that when running a Jeep KJ. The front diff housings are aluminum on those and a spinning wheel suddenly gaining traction would often shatter them, or break an axle or CV as you say. However, trucks with an ARB in the front diff would ultimately work better because it equalized the two sides. The diff was still weak but the whole was more reliable with the locker. If one didn't get stupid with it, that is.

 

[zimm]

Two videos done by 4wd action in Australia were the compare ATRAC to diff locks.

http://www.youtube.com/watch?v=C2wkW...e_gdata_player

http://www.youtube.com/watch?v=YNFac...e_gdata_player

Here is a thread on toyota120 talking about ATRAC
http://www.toyota120.com/forum/showthread.php?t=244&highlight=atrac
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the first two links are dead, and the last one is long. any concept we should be paying attention to, prior to reading it?

pmed you

 

[zimm]

It all depends on the driver and conditions. In a rock crawling situation, I believe A-Trac would cause differential and axle damage before a locker would, particularly if the vehicle is being driven appropriately. A-Trac requires wheel spin to activate. A wheel that is spinning, then suddenly making contact with a high traction surface (like Moab slick rock) is a lot more likely to cause damage then a slowly rotating and locked wheel.

The counterpoint would be A-Trac in a tight turn. Drivers typically do not know the stress a locker can impart in a tight turn, particularly with a CV axle. Overall, lockers driven properly are much more gentle on the truck and terrain than traction control. . .

sure it needs to slip, but even if its slipping at a high rate of speed initially, a brake itself cant brake an axle, and the kinetic energy of the spinning tire is being given off as heat by the brake. it never sees the axle. the only energy the axle sees is from the motor, and its at best 1/2 the torque, unlike a locker.

atrac doesnt do a thing if the fuel is mashed. you have to going slow to use atrac in the first place. what you are saying then, is the spinning tire of an open diff has more carnage associated with than atrac?

perhaps the vids above that wont boot have the scenario you speak of.

 

[madmax718]

I havent used Atrac, so I can't say. But I would assume that as long as it can control throttle and wheel spin, I wouldn't expect atrac to be a bit softer on the components, then say, a fully open diff suddenly gaining traction.

I just dont know how much wheel spin the system allows- how it works, can I idle over obstacles, or does atrac need throttle input before it will work- apparently it turns off when braking.

If the sensors and computers are fast enough, it will work fine. Except that it seems that one wheel in the air makes atrac fully stop the one wheel without traction and transfer it all to the other wheel.

Still not as soft as a locker IMHO.

 

[zimm]

I experienced that when running a Jeep KJ. The front diff housings are aluminum on those and a spinning wheel suddenly gaining traction would often shatter them, or break an axle or CV as you say. However, trucks with an ARB in the front diff would ultimately work better because it equalized the two sides. The diff was still weak but the whole was more reliable with the locker. If one didn't get stupid with it, that is.

for apples to apples, i was sort of limiting this to the atrac available trucks. one could easily make the argument that that is just a crappy diff. ive seen locked jeep rears catch and take out the tcase. if a truck has parts that are plain ol undersized, something ends up breaking no matter what.

 

[zimm]

I havent used Atrac, so I can't say. But I would assume that as long as it can control throttle and wheel spin, I wouldn't expect atrac to be a bit softer on the components, then say, a fully open diff suddenly gaining traction.

I just dont know how much wheel spin the system allows- how it works, can I idle over obstacles, or does atrac need throttle input before it will work- apparently it turns off when braking.

If the sensors and computers are fast enough, it will work fine. Except that it seems that one wheel in the air makes atrac fully stop the one wheel without traction and transfer it all to the other wheel.

Still not as soft as a locker IMHO.

its equal and opposite. the wheel with traction can only supply the same amount of force going to the braked wheel, so, its at best 1/2. there is no "transfer" of force in an open diff, only a matching of force.

 

[Ryanmb21]

the first two links are dead, and the last one is long. any concept we should be paying attention to, prior to reading it?

pmed you

The links should be fixed now. The thread over on 120 is broad but I thought it would be a good read for folks interested to learn more about ATRAC. The talk goes back to 2006 and folks share their experiences as they got better at using it.

 

[zimm]

Two videos done by 4wd action in Australia were the compare ATRAC to diff locks.

http://youtu.be/C2wkW05Pc6c

http://youtu.be/YNFacsKnswM

Here is a thread on toyota120 talking about ATRAC
http://www.toyota120.com/forum/showthread.php?t=244&highlight=atrac
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odd. at 3.00 in the second vid, traction control was working EXACTLY how it was supposed to, and was driven in how you drive it in to an obstacle. he sad it was "over ridden" and it wasnt.

 

[zimm]

notice how there is no spinning tire to suddenly catch and snap axles... http://www.youtube.com/watch?v=fk6ARzFBBQk

notice how you suddenly want to punch carl weathers in slow motion by the end of the vid.

 

[Ryanmb21]

odd. at 3.00 in the second vid, traction control was working EXACTLY how it was supposed to, and was driven in how you drive it in to an obstacle. he sad it was "over ridden" and it wasnt.

I do see that, I agree with you. Looks like Atrac worked fine.

 

[proper4wd]

Here's the issue,

Traction control of any kind (not just "ATRAC"), works by applying the brakes to a wheel to equalize the resistance between the two wheels, in order to try to make both wheels turn at the same speed.

If wheel A is on solid rock and needs to pull the vehicle forward, it may take 1000 ft lbs of torque to turn.

If wheel B is in midair, it will take essentially 0 ft lbs of torque to turn. So traction control will apply the brakes to wheel B until approximately 1000 ft lbs of resistance is achieved and both front wheels will turn.

You are now putting 2000 ft lbs of torque through the front driveline and differential to move the vehicle forward, with 1000 ft lbs to each wheel.

With a locked diff, the vehicle would move with just 1000 ft lbs of torque through the front driveline and differential. With just 1000 ft lbs to wheel A and 0 ft lbs to wheel B.

 

[proper4wd]

As a followup post (I'll let that one sink in), at the limits of torque application yes the locking diff has the ability to break more components because it has the ability to transfer 100% of available torque to one wheel whereas the traction control system will constantly be trying to give each wheel 50% of the available torque at that axle.

250ft lbs engine torque x 60:1 gear reduction = 15,000 ft lbs available max torque. Applied to just one axle shaft this will break even the strongest Dana 60. Truthfully even half that would break most differentials.