'01-up 4wd System (A-TRAC, VSC) and TORSEN T-3
- Thread starter Thai
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Thai
Elite Member
An article in the current Motor Trend (a "Perspective" by Dan Carney) talks about skid control systems and studies that have shown how effective they are.
A few quotes: "Mercedes-Benz's research cites a 29-percent reduction in single-car accidents and a 15-percent reduction in overall crashes, thanks to stability control. Deadly high-speed wrecks were slashed 55 percent." "DEKRA Automotive Research, in Germany, found a 27-percent drop in serious loss-of-control crashes. Toyota reports a 35-percent drop in single-car crashes and a 30-percent reduction of head-on crashes in Japan."
Toyota's study was comparing accident rates of the same vehicle with and without VSC.
A few quotes: "Mercedes-Benz's research cites a 29-percent reduction in single-car accidents and a 15-percent reduction in overall crashes, thanks to stability control. Deadly high-speed wrecks were slashed 55 percent." "DEKRA Automotive Research, in Germany, found a 27-percent drop in serious loss-of-control crashes. Toyota reports a 35-percent drop in single-car crashes and a 30-percent reduction of head-on crashes in Japan."
Toyota's study was comparing accident rates of the same vehicle with and without VSC.
tundra_stl
New member
So just to clarify if I want to get 50-50 4x4 I would turn off VSC on my 03 V8 ? But If I run with it on all the time i'm 30% to the front..and 70% to the rear..am I correct? I have turned it off in the snow once and the VSC lite was flashing thats normal?? Little confused cause this baby dont get off road with the wife driving it ..just some snow sometimes. Please clarify
TIA
TIA
Thai
Elite Member
If you want 50/50 split ALL THE TIME, then you need to lock the center differential (which will also turn OFF VSC).
If you do not lock the center diff, then the Torsen will split torque on it's own. That is, in normal driving with no slippage, 70% of power will go the rear and 30% to the front. If there's slippage detected on the rear axle (either or both tires), then more power is shifted to the front wheels. And vice-versa. That's the beauty of Torsen center diff and similar differentials on Toyota since 1999.
Basically, the Torsen does allow power to ALWAYS flow to BOTH axles. The only difference is that Torsen controls the distribution of torque ("how much"). When you lock the center diff, then you basically telling Torsen to ALWAYS give 50% of power to each axle ("don't think, just do it my way"). This is helpful in off-roading when you don't want the Torsen computer to "overthink" itself or disrupt traction by shifting torque back and forth.
When you lock the center diff, the VSC light should NOT blink. Read this thread:
http://www.toyota-4runner.org/showthread.php?s=&threadid=92
Hope this helps.
If you do not lock the center diff, then the Torsen will split torque on it's own. That is, in normal driving with no slippage, 70% of power will go the rear and 30% to the front. If there's slippage detected on the rear axle (either or both tires), then more power is shifted to the front wheels. And vice-versa. That's the beauty of Torsen center diff and similar differentials on Toyota since 1999.
Basically, the Torsen does allow power to ALWAYS flow to BOTH axles. The only difference is that Torsen controls the distribution of torque ("how much"). When you lock the center diff, then you basically telling Torsen to ALWAYS give 50% of power to each axle ("don't think, just do it my way"). This is helpful in off-roading when you don't want the Torsen computer to "overthink" itself or disrupt traction by shifting torque back and forth.
When you lock the center diff, the VSC light should NOT blink. Read this thread:
http://www.toyota-4runner.org/showthread.php?s=&threadid=92
Hope this helps.
tundra_stl
New member
I think your reply helps...in a nutshell..VSC on center diff unlocked...VSC off center diff locked 50/50 ,in most cases the Torsen does all the thinking and you would only 50/50 if you need to override the "thinking" of the Torsen in a "offroad" situation but it not daily driving ..the wife dont do off road 
My Tundra 4x4 is either on..or off ..when you think about it its a real neat system on the 4runner... thanks for the info Thai.
My Tundra 4x4 is either on..or off ..when you think about it its a real neat system on the 4runner... thanks for the info Thai.
Thai
Elite Member
Yup, you got it! 
I heard a rumor that the Tundra and Tacoma will soon have a similar 4wd system as the 4runner/Land Cruiser...that is, it's ABS-based 4-wheel traction control system (ATRAC). It SHOULD have been this year (2004). In fact, initial literature from Toyota shows the Tacoma to have a similar system...however, it seems like Toyota is waiting another year before implementing it. Hopefully, they will use the system in 2005 for all of it's 4x4.
I heard a rumor that the Tundra and Tacoma will soon have a similar 4wd system as the 4runner/Land Cruiser...that is, it's ABS-based 4-wheel traction control system (ATRAC). It SHOULD have been this year (2004). In fact, initial literature from Toyota shows the Tacoma to have a similar system...however, it seems like Toyota is waiting another year before implementing it. Hopefully, they will use the system in 2005 for all of it's 4x4.
Thai
Elite Member
Here is an excellent owner's writeup on the VSC/ATRAC system on ice: (It is written by CORANCHER on the Edmunds.com forum)
Last night we got just the right kind of slick snow and ice for experimenting on a very low traction surface, so I went out shortly after midnight on local streets and a couple of big parking lots to see what I could learn. I thought I'd share my experiences here and see how they compare with those of others. First (in case you don't want to read the detail) I thought I'd list the main conclusions I came to:
1. The system is very effective, and doesn't require that the user do anything different in typical situations.
2. Traction is much better (more than twice as good) in 4WD, so if you've got a V6 (with its multimode system) I recommend you switch to 4WD at your first opportunity or just leave it there any time things might get slick.
3. Traction enhancements, especially 4WD and traction control, don't change the ultimate adhesion limits for turning and braking. Those limits on the "friction circle" remain, so technology can actually allow you to get to hazardous speeds easier/quicker than before.
And now more detail on my experiences and some speculation on the hows and whys. First, I should note that I was alone in the vehicle with no cargo, so the rear end was light. I've got a V6 so I experimented in both 2WD and 4WD modes. I was running in just a couple of inches of snow near the freezing point, and the snow would pack immediately into ice when driven on (or especially when spun on) so conditions were very slick but not what I would call extremely slick.
I started out in 2WD. Even on level streets or slight slopes it was easy to get traction control (TC) and skid control (SC) working, whether accelerating from a stop or just speeding up, and whether going straight or turning. The main clue that the system is working is the noise from the pump recharging the pressure accumulator (sounds like a chattering sound or the sound of a chain slipping on loose sprockets) and the light in the instrument cluster. The pump noise often persists for a few seconds after the system has stopped acting. Other clues are the dull thunks coming from the brakes stopping or starting wheel rotation and the feel of the system doing something unusual like braking only one side to straighten you out. If you pay attention you can also feel the dethrottling.
In general I don't think traction was very good in 2WD with no weight in back. I think the Bridgestone Duelers are ok in these conditions; no better and no worse. Most folks aren
Last night we got just the right kind of slick snow and ice for experimenting on a very low traction surface, so I went out shortly after midnight on local streets and a couple of big parking lots to see what I could learn. I thought I'd share my experiences here and see how they compare with those of others. First (in case you don't want to read the detail) I thought I'd list the main conclusions I came to:
1. The system is very effective, and doesn't require that the user do anything different in typical situations.
2. Traction is much better (more than twice as good) in 4WD, so if you've got a V6 (with its multimode system) I recommend you switch to 4WD at your first opportunity or just leave it there any time things might get slick.
3. Traction enhancements, especially 4WD and traction control, don't change the ultimate adhesion limits for turning and braking. Those limits on the "friction circle" remain, so technology can actually allow you to get to hazardous speeds easier/quicker than before.
And now more detail on my experiences and some speculation on the hows and whys. First, I should note that I was alone in the vehicle with no cargo, so the rear end was light. I've got a V6 so I experimented in both 2WD and 4WD modes. I was running in just a couple of inches of snow near the freezing point, and the snow would pack immediately into ice when driven on (or especially when spun on) so conditions were very slick but not what I would call extremely slick.
I started out in 2WD. Even on level streets or slight slopes it was easy to get traction control (TC) and skid control (SC) working, whether accelerating from a stop or just speeding up, and whether going straight or turning. The main clue that the system is working is the noise from the pump recharging the pressure accumulator (sounds like a chattering sound or the sound of a chain slipping on loose sprockets) and the light in the instrument cluster. The pump noise often persists for a few seconds after the system has stopped acting. Other clues are the dull thunks coming from the brakes stopping or starting wheel rotation and the feel of the system doing something unusual like braking only one side to straighten you out. If you pay attention you can also feel the dethrottling.
In general I don't think traction was very good in 2WD with no weight in back. I think the Bridgestone Duelers are ok in these conditions; no better and no worse. Most folks aren
hillbilly
New member
Thai-
Correct me if I'm wrong, but Active TRAC (A-TRAC) can be disabled. The ONLY way, that I'm aware of anyway, that the A-TRAC system can be disabled is when the T-case is put in 4Lo (VSC off) AND the transmission is ALSO in Lo (1st gear.) Anything other than 4Lo/Lo (4Lo/2nd or 3rd, 4Hi/Lo) and the A-TRAC system will remain active and engage if any of the wheels begin to slip/spin.
Spinning the tires in anything other than 4Lo/Lo and you should hear the A-TRAC (ABS) system ratcheting the brake calibers trying the limit the spinning.
Two words of caution: (1)Excessive and prolonged tire spinning in anything other than 4Lo/Lo can cause the A-TRAC (ABS) system to overheat and temporarily shut down (indicated by the "TRAC OFF" light on the instrument cluster) until it cools off. Once cooled to an acceptable temp, the A-TRAC (ABS) will automatically re-engage. (2) Be careful not to over-rev the engine if you want to burn out in 4Lo/Lo. Oh yea... and hold on tight (high rpm + low torgue = lots of power).
Correct me if I'm wrong, but Active TRAC (A-TRAC) can be disabled. The ONLY way, that I'm aware of anyway, that the A-TRAC system can be disabled is when the T-case is put in 4Lo (VSC off) AND the transmission is ALSO in Lo (1st gear.) Anything other than 4Lo/Lo (4Lo/2nd or 3rd, 4Hi/Lo) and the A-TRAC system will remain active and engage if any of the wheels begin to slip/spin.
Spinning the tires in anything other than 4Lo/Lo and you should hear the A-TRAC (ABS) system ratcheting the brake calibers trying the limit the spinning.
Two words of caution: (1)Excessive and prolonged tire spinning in anything other than 4Lo/Lo can cause the A-TRAC (ABS) system to overheat and temporarily shut down (indicated by the "TRAC OFF" light on the instrument cluster) until it cools off. Once cooled to an acceptable temp, the A-TRAC (ABS) will automatically re-engage. (2) Be careful not to over-rev the engine if you want to burn out in 4Lo/Lo. Oh yea... and hold on tight (high rpm + low torgue = lots of power).
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Thai
Elite Member
Hillbilly,
I have not heard that you can turn off ATRAC, even in the situation you described. If this is true, then you should see "TRAC OFF" when you're in 4-LO and 1st gear, right?? From my past off-roading with my 4runner, this does NOT turn off ATRAC. For me, ATRAC is always ON. You can only manipulate VSC.
Now, on Sequoia, i think that you have to be in 4-LO and 1st gear to turn OFF VSC. This is not the case with the 4runner.
Have you tried this on your 4runner??
I have not heard that you can turn off ATRAC, even in the situation you described. If this is true, then you should see "TRAC OFF" when you're in 4-LO and 1st gear, right?? From my past off-roading with my 4runner, this does NOT turn off ATRAC. For me, ATRAC is always ON. You can only manipulate VSC.
Now, on Sequoia, i think that you have to be in 4-LO and 1st gear to turn OFF VSC. This is not the case with the 4runner.
Have you tried this on your 4runner??
ToolmanJohn
New member
Yeah. In my Limited 4x4 2003 4runner, VSC is always on, except when the center differential is locked.
It is VERY aggresive at limiting wheelspin in 2wd mode, but that's what happens when you put 245hp to 2 wheels. I haven't been able to get it to activate when in 4wd mode on dry roads. By distributing the power to 4 wheels, the torsen differential pretty much lets all wheels get what they can handle.
As far as driving around without VSC, I am glad it's there, the saftey features that make this truck so nice are one of the prime reasons I bought it. I wouldn't bother locking the center diff. unless going off-road where I knew conditions would be slippery (low and slow) or on road up very slippery hills, where VSC "may" halt your progress. I haven't encountered a snow covered hill the 4runner couldn't eat yet though, in normal 4wd.
On a final note, 2wd mode with the stock HT840 tires is USELESS on snow!! The truck is crippled, and darn it takes FOREVER to accelerate. 4wd is great, even with VSC.
It is VERY aggresive at limiting wheelspin in 2wd mode, but that's what happens when you put 245hp to 2 wheels. I haven't been able to get it to activate when in 4wd mode on dry roads. By distributing the power to 4 wheels, the torsen differential pretty much lets all wheels get what they can handle.
As far as driving around without VSC, I am glad it's there, the saftey features that make this truck so nice are one of the prime reasons I bought it. I wouldn't bother locking the center diff. unless going off-road where I knew conditions would be slippery (low and slow) or on road up very slippery hills, where VSC "may" halt your progress. I haven't encountered a snow covered hill the 4runner couldn't eat yet though, in normal 4wd.
On a final note, 2wd mode with the stock HT840 tires is USELESS on snow!! The truck is crippled, and darn it takes FOREVER to accelerate. 4wd is great, even with VSC.
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ToolmanJohn
New member
Thai is right. The Torsen3 center differential is only on 4wd versions (V6 or V8).
If someone gave me the complete electrical schematic I could probably find a way to deactivate the VSC without shutting off the anti-lock brakes.
If someone gave me the complete electrical schematic I could probably find a way to deactivate the VSC without shutting off the anti-lock brakes.
Thai
Elite Member
delrmx01 said:
Unless you off-road a lot or use it over rough terrain, you probably don't need lockers or LSDs. Your 2wd 4runner ALREADY has traction control on the rear wheels, which provides a PSEUDO-LSD. That is, it is as effective as LSD. It is not as good as a true locker though.
HiluxSurf SSR-G
Senior Member
Excellent work Thai!
Just a few clarificatory questions, I hope you won't mind.
My Surf has the A340F A/T transmission (don't know if it matters), can I fit a torsen center diff?
Can I fit a torsen LSD into my current differentials, front & rear?
Thanks.
Just a few clarificatory questions, I hope you won't mind.
My Surf has the A340F A/T transmission (don't know if it matters), can I fit a torsen center diff?
Can I fit a torsen LSD into my current differentials, front & rear?
Thanks.
