ATRAC effectiveness - Take Two

[sonk76]

Ok. I posted a couple of months ago my experience in testing ATRAC in a deep snow bank (it didn't/couldn't spin the one tire with traction when rest of the truck was stuck in the snow bank).

Now I have a fresh experience from last weekend's off-road outing, where the rear tire was not spinning as I had hoped. I attempted a hill climb section and the rear driver's side tire failed to turn even with ATRAC seemingly trying to do it's thing. This time I'm a little moredis appointed in the outcome as this was a "real world" test of the system, and it didn't perform as I had hoped. See link below:

YouTube - IMG_0374_ATRAC.MOV

Over the course of the day I observed that in general the system seemed to work well (e.g., in situations with wheels off the ground I was able to continue moving forward), and the system seems very good on the front tires (i.e., I've never observed a situation where it was unable to get a front tire with more traction to spin).

So in summary: front ATRAC good/great, rear ATRAC "mediocre"

As a matter of fact I can not be certain whether or not it was always simply the front ATRAC system that enabled me to continue in the wheel off the ground scenarios, or if it was the front and rear together doing this.

This made me wonder some more as to are there any more definitive ways in which I could test whether or not my ATRAC is working to the intended specifications of the manufucturer (particularly with the rear tires)? I was thinking that there must be some kind of a diagnostic mechanism by which the manufacturer is able to test/service these systems (even if the dealership is not quite so clear on them.)

Sure would have loved to have had another 100 out there with us to do a side-by-side comparison (not really easy to compare situations that are "similar", because so many variables are involved, unless it is exact same place/day/time)...

 

[2000UZJ]

ATRAC is definitely not "biting" like it should. Mine is almost to "bitey"(not a word but you get the piont)

YouTube - ATRAC violently stopping a wheel

I am wondering why yours does not transfer power (enough to put you over the top of that, it's not a very steep hill according to the camera and not too off camber, even with a stuffed front wheel and rear wheel loosing traction it will shoot me over the hill). ATRAC also will grab the back wheels just as hard as the front. I'm going to assume you were in low with CDL on. Have you tried just holding the throttle @ 1500-2K for a long time to see what happens?

EDIT: I watched it again, only way mine will do that is with the center diff unlocked, have you checked to make sure the center diff fully engages? I have trouble climbing off camber obstacles with the CDL off...

 

[sonk76]

ATRAC is definitely not "biting" like it should. Mine is almost to "bitey"(not a word but you get the piont)

YouTube - ATRAC violently stopping a wheel

I am wondering why yours does not transfer power (enough to put you over the top of that, it's not a very steep hill according to the camera and not too off camber, even with a stuffed front wheel and rear wheel loosing traction it will shoot me over the hill). ATRAC also will grab the back wheels just as hard as the front. I'm going to assume you were in low with CDL on. Have you tried just holding the throttle @ 1500-2K for a long time to see what happens?

Yes, CDL on, Low range. Holding RPM steady at 1.5 - 2k

 

[2000UZJ]

Yes, CDL on, Low range. Holding RPM steady at 1.5 - 2k

When I go out Friday, I know a hill that looks almost identical to the one in your video, I'll take a few videos (high with open/locked CDL and same in low range) and post for you. I'm looking on my computer to see if I have one similar. That is strange though, could it possibly be the ECU? I'm knowledgeable when it comes to wheeling with ATRAC, just not very knowledgeable on how and where to look for problems. When my rear wheel comes off the ground it WILL lock it up until it comes in contact with the ground again.

 

[arbetrader]

After taking toyota university's course on this topic (I know that sounds laughable, but that's what they call it for employees, lol) and learning firsthand from the developers, I believe your system is not functioning correctly; something is wrong there. There should be at least some wheel movement on the left rear wheel there, especially after holding rpms steady. You should put your vehicle in the air (all 4 wheels), and apply power to all wheels with the center diff locked to see what happens, and how different it is with it unlocked. My guess is that even though your system indicates the center diff is locked, there is a malfunction somewhere. It seems to be operating as it would with the center diff unlocked. At least to me....

 

[sonk76]

After taking toyota university's course on this topic (I know that sounds laughable, but that's what they call it for employees, lol) and learning firsthand from the developers, I believe your system is not functioning correctly; something is wrong there. There should be at least some wheel movement on the left rear wheel there, especially after holding rpms steady. You should put your vehicle in the air (all 4 wheels), and apply power to all wheels with the center diff locked to see what happens, and how different it is with it unlocked. My guess is that even though your system indicates the center diff is locked, there is a malfunction somewhere. It seems to be operating as it would with the center diff unlocked. At least to me....

Great to get some info close to the source!

With respect to the CDL, I strongly suspect that it (CDL) is working as intended: 1) I can observe significant difference in the offroad capability with it locked 2) I can sense greater difficulty when turning on high traction surfaces when it is on (i.e., symptom of locked center differential, and the binding it creates when trying to turn on hard surface) 3) in all cases with the CDL on (locked), the rear of the truck is receiving power because at least one of the tires is spinning (if it were not working, then I could observe situations where only the front tires are spinning [assuming that ATRAC was not intervening])

That said, if I were to have my truck in the air, with all four tires of the ground, what should I be observing to help diagnose?

My guess is that if all 4 wheels are off the ground, then regardless of whether or not CDL is engaged all 4 wheels will spin at equal rates--unless one or more of the wheels are somehow binding, or otherwise have problems...

 

[sonk76]

When I go out Friday, I know a hill that looks almost identical to the one in your video, I'll take a few videos (high with open/locked CDL and same in low range) and post for you. I'm looking on my computer to see if I have one similar. That is strange though, could it possibly be the ECU? I'm knowledgeable when it comes to wheeling with ATRAC, just not very knowledgeable on how and where to look for problems. When my rear wheel comes off the ground it WILL lock it up until it comes in contact with the ground again.

Sounds great, and thank you for doing this.

Btw, despite what it looks like in the video, this is really a pretty steep incline (below is a photo that I've straightened to reflect what it actually looks like--you can see that all the trees are now vertical, vs. in the video they are leaning because the camera is tilted. Given the steepness and the semi-loose gravel, I'm not sure that even with lockers I could have crawled up that thing... now with a bit of momentum, I'm sure it would have worked out with/without lockers. A locked rubicon on 35" KM2's went up this successfully right after me, but they used a bit more momentum to their advantage too...

 

[re_guderian]

Did you ever check whether your rear brake calipers were binding/siezed?



Soon as I figure out how to upload a youtube, I'll show you what it looks like for mine. The rear works just as well as the front.

Was your passenger's side rear spinning freely?

 

[Topmounter]

Weird, something is definitely not right between the CD and the rear wheels. Could something have failed in the rear diff or one of the rear axles that is keeping power from getting transferred properly?

 

[2000UZJ]

Sounds great, and thank you for doing this.

Btw, despite what it looks like in the video, this is really a pretty steep incline (below is a photo that I've straightened to reflect what it actually looks like--you can see that all the trees are now vertical, vs. in the video they are leaning because the camera is tilted. Given the steepness and the semi-loose gravel, I'm not sure that even with lockers I could have crawled up that thing... now with a bit of momentum, I'm sure it would have worked out with/without lockers. A locked rubicon on 35" KM2's went up this successfully right after me, but they used a bit more momentum to their advantage too...

anytime, that does look a bit steeper in the picture since it is level now.

did you try the momentum on your side?

 

[sonk76]

Did you ever check whether your rear brake calipers were binding/siezed?

I tried to visually check, but I wasn't quite sure what to "look" for. The brakes seem to work fine, and even the ATRAC seems to work in the rear, it's just that it seems "weak" relative to the ATRAC on the front...

Soon as I figure out how to upload a youtube, I'll show you what it looks like for mine. The rear works just as well as the front.

Was your passenger's side rear spinning freely?

Yes, passenger's side rear tire was spinning freely the whole time

 

[sonk76]

anytime, that does look a bit steeper in the picture since it is level now.

did you try the momentum on your side?

As a matter of fact I did, here is a brief video of the subsequent attempt:

YouTube - Hill Climb

...made it further, but still did not make it. I believe I was high-centered so I wasn't able to clear the top. I don't have good ATRAC data points from this one (front seems to work well, as always), but I don't have a record of what the rear was doing--I do know that this time the driver's side rear tire was spinning (not seen in video), but I don't remember what the passanger's side rear tire was doing at the same time.

 

[re_guderian]

I tried to visually check, but I wasn't quite sure what to "look" for. The brakes seem to work fine, and even the ATRAC seems to work in the rear, it's just that it seems "weak" relative to the ATRAC on the front...




Yes, passenger's side rear tire was spinning freely the whole time

You won't be able to visually check. Following the procedures for a changing a brake pad, you will have to push the pistons back into the bore to make room for a new (thicker) pad. If the piston is siezed in the bore, you won't be able to push it back. The freely spinning rear passenger wheel is not right.

 

[sonk76]

You won't be able to visually check. Following the procedures for a changing a brake pad, you will have to push the pistons back into the bore to make room for a new (thicker) pad. If the piston is siezed in the bore, you won't be able to push it back. The freely spinning rear passenger wheel is not right.

Thanks. Is this an easy job to do at home with limited tools?

 

[ShottsUZJ100]

As a matter of fact I did, here is a brief video of the subsequent attempt:

YouTube - Hill Climb

...made it further, but still did not make it. I believe I was high-centered so I wasn't able to clear the top. I don't have good ATRAC data points from this one (front seems to work well, as always), but I don't have a record of what the rear was doing--I do know that this time the driver's side rear tire was spinning (not seen in video), but I don't remember what the passanger's side rear tire was doing at the same time.

You need another inch lift (not lockers)!

The first posted video again has my gut saying something is not right in the rear. OK...that hill is very steep and the dirt at the rear wheels is really soft. Regardless, at some point you should see that rear wheel jerk though it never does.

In my video below...it's a situation where a locker is better than TRAC. Watch the DS rear and PS front wheels stop and start throwing dirt. These are the extended wheels with almost no traction.

Everytime that DS rear stops throwing dirt the PS rear is getting torque. You don't see the PS wheel move however because:

*Traction is quite good so it doesn't spin
*Not enough torque to move the vehicle forward or spin that wheel from a dead stop
(Granted, had I not of stopped cold to take the video I'd a driven through on momentum)(I also promise you TRAC could have got me out if this...just a bit more gas though the more gas you use the more you risk....and tear up tires)

You can tell however that power keeps getting moved around from side to side and at both axles by the dirt getting flinged on and off. I would bet on your original video that your PS rear NEVER stopped throwing dirt/spinning (meaning torque never got transferred to the DS rear).

Charouleau Gap (to see trail maintenance) 3/10 UZJ100 - John Shotts (shottscruisers)'s Photos

 

[sonk76]

In my video below...it's a situation where a locker is better than TRAC. Watch the DS rear and PS front wheels stop and start throwing dirt. These are the extended wheels with almost no traction.

Charouleau Gap (to see trail maintenance) 3/10 UZJ100 - John Shotts (shottscruisers)'s Photos

Thanks for sharing that video. I'm excited to finally see another video of ATRAC where the system does not seem to be able to apply quite enough torque to the tire with more traction to get it to spin. This makes me feel a little more comfortable in that my ATRAC system may not be "broken" after all, but rather that I'm simply reaching the limits of the system.

I'm going to keep on diagnosing it.

I'm planning on going out to Rausch Creek again on Saturday April 24th, in case anyone with a 100 can make it at the same time. Would love to do some side-by-side comparisons to draw more definitive conclusions (I'm holding out hope that one of these days I'll end up wheeling with another 100 yet--so far it's 95% jeeps out there...)

 

[BROKEROB1]

I may try to make it out to Rausch on the 24th, as I am also wondering and it would be interested to compare ATRAC systems, as well. I am thinking having another similar rig run an identical line may be the easiest way for you to diagnose a normally operating system vs. a problem.

...I can hear the excuses to already... I have to do it for the mud guys!

Thanks for sharing that video. I'm excited to finally see another video of ATRAC where the system does not seem to be able to apply quite enough torque to the tire with more traction to get it to spin. This makes me feel a little more comfortable in that my ATRAC system may not be "broken" after all, but rather that I'm simply reaching the limits of the system.

I'm going to keep on diagnosing it.

I'm planning on going out to Rausch Creek again on Saturday April 24th, in case anyone with a 100 can make it at the same time. Would love to do some side-by-side comparisons to draw more definitive conclusions (I'm holding out hope that one of these days I'll end up wheeling with another 100 yet--so far it's 95% jeeps out there...)

 

[re_guderian]

Thanks for sharing that video. I'm excited to finally see another video of ATRAC where the system does not seem to be able to apply quite enough torque to the tire with more traction to get it to spin. This makes me feel a little more comfortable in that my ATRAC system may not be "broken" after all, but rather that I'm simply reaching the limits of the system.

I'm going to keep on diagnosing it.

I'm planning on going out to Rausch Creek again on Saturday April 24th, in case anyone with a 100 can make it at the same time. Would love to do some side-by-side comparisons to draw more definitive conclusions (I'm holding out hope that one of these days I'll end up wheeling with another 100 yet--so far it's 95% jeeps out there...)

notice John's DS rear wheel. It is not "free spinning", rather "jerking" as the ATRAC grabs and releases, sending pulses of dirt back. Is that what your PS rear wheel was doing?

 

[2000UZJ]

notice John's DS rear wheel. It is not "free spinning", rather "jerking" as the ATRAC grabs and releases, sending pulses of dirt back. Is that what your PS rear wheel was doing?

I think some left foot braking could pull you out with a little work and time.


just don't let it bounce to much or she will go "pop pop pop" and thar goes yer axle.

 

[re_guderian]

I think I finally joined the YouTube world... Like your pictues, its steeper than it looks in the video. Understand that traction, tire pressure, blah blah blah is all different...