'01-up 4wd System (A-TRAC, VSC) and TORSEN T-3 - Page 2 - Toyota

Thai · 10-10-2003, 08:51 AM

patin,

1. As long as you don't lock the center diff, you can drive in 4wd all you want at any speed. (Note: Nissan Pathfinder's AWD system IS supposedly restricted to 55-65 mph...crappy system!) Once you are in 4wd, the system is FULL-TIME, just like in the Land Cruiser/new 4runner V8/Lexus. Therefore, i have never heard of such restriction.

2. If you lock your center diff, then it is advisable to do it on SLIPPERY surfaces. However, you can drive in a STRAIGHT line all you want. The only problem is when you start to make a turn...this can cause binding in the lock center diff...over time, this will wear out the center diff gearing and cause damage. Thus, you lock the center diff ONLY when off-roading where gear binding is minimized due to slippery surfaces (dirt, gravel, mud, etc.).

3. Once you lock the center diff, your VSC is turned OFF. The reason you still see lights flashing and weird noises is because 4-WHEEL TRACTION CONTROL (ATRAC) is still operating, braking the wheel(s) that are slipping.

The faster your rev your engine, the less traction control intervenes. For example, if you're gunning up a muddy hill, then you need to be more aggressive with the gas pedal. I think that ATRAC cuts down it's braking above 2500-3500 rpms. So, you can power up the muddy hill, with all wheels spinning. ATRAC is mostly for lower speeds.

Hope this helps.

Thai · 10-10-2003, 09:09 AM

Link:

TORSEN Traction Differential T-3 (Type 3 or Type C)

TYPE 3 TRACTION DIFFERENTIAL
Zexel Torsen's new generation T-3 Traction Differential are ideally suited for center applications, dividing torque front to rear in all-wheel drive vehicles. Similar to the T-2 parallel axis differential, the T-3 uses helical planetary gears which pilot on their outside diameter. The T-3, however, uses an extremely compact planetary gear configuration capable of nominal torque splits other than 50/50. The planetary nature of the design allows for a forward or rearward biased torque split.

Unlike conventional speed sensing, limited-slip differentials, TORSEN T-3 is a full-time torque-sensing, torque biasing system. Torque and differentiation are continuously managed between the front and rear axles and biased instantaneously according to variable road conditions, automatically shifting the power to the wheel with the most traction before any wheel slip can occur. There are no clutches or preload to worry about, in fact, the TORSEN T-3's patented helical planetary gearing system is designed to PERFORM FOR THE LIFE OF THE VEHICLE.

TORSEN T-3 Traction Differentials are available with a locking capability range of 20-30% and a nominal split from 65:35 and 35:65, front to rear. The T-3 can be designed to fit most transmissions or transaxles with no modifications required. In addition, it is fully compatible with ABS, Traction Control Systems, and Stability Control Systems, providing the ultimate traction management systems.

Thai · 10-10-2003, 09:15 AM

MULTIFUNCTION CAPABILITIES
The TORSEN T-3 is an advanced, multi-function traction system providing continuous, uninterrupted torque output, splitting, biasing, and differentiation in one integral unit. It is always active, responding instantly to torque feedback from variable driving conditions.

ENHANCED PERFORMANCE
The TORSEN T-3's capability to immediately respond to variable driving conditions not only provides better traction, it also enhances the general performance of a vehicle. There is a marked improvement in total tractive effort as compared to open or speed-sensing center differential equipped vehicles. In addition, the exceptional efficiency of the T-3 allows the engine's torque to be used more effectively, delivering more horsepower to the road. The combined improvement in traction and the augmented power results in a nimble yet sure-footed vehicle that provides better handling, increased acceleration and an improved margin of safety.

LOCKING EFFECT

(FRICTION INTERFACE SURFACES)

Side Gear Thrust to Housing
Planet Gear Separation to Planet Carrier
Planet Gear Thrust to Planet Carrier
Helical Tooth Mesh

Designed for today's modern all-wheel drive vehicles, the TORSEN T-3 Traction Differential is also suited for any application where a planetary differential is desired. TORSEN T-3 advantages include helical planetary gear design allowing front or rear biased asymmetrical torque splits under normal conditions. In addition, the number of planet gears can be increased or decreased, based upon system strength requirements.

DESIGNED FOR HARD-TO-PACKAGE ALL-WHEEL DRIVE SYSTEMS
The new generation TORSEN T-3 Traction Differential provides efficient torque splitting, biasing, and differentiation for improved vehicle performance. It is specifically engineered for hard to package all-wheel drive trains and is compatible with all automatic transmission fluids. The unique (patent pending) Twin Differential configuration makes the TORSEN T-3 especially well suited for front wheel drive based applications that relied on external-mounted torque-on-demand couplings to drive the rear axle. The Twin Differential offers the most compact all-wheel drive package with the greatest strength, while providing all the traction benefits of a TORSEN differential. With the TORSEN T-3, the vehicle has true all-wheel drive, driving all the wheels all the time. This can provide optimal traction management and deliver more power to the wheels, resulting in improved vehicle stability, handling, and performance.

TORSEN T-3 IS AVAILABLE FOR ALL SPLIT AND LOCKING AFFECT REQUIREMENTS

Zexel Torsen, Inc. will custom design, engineer, test, and manufacture the TORSEN T-3 Traction Differential to meet your specific torque split and locking affect requirements. Advanced TORSEN T-3 technology is a perfect match for applications with ABS, Traction Control, and stability control/vehicle dynamics systems, providing the ultimate traction control platforms for your vehicle.

patin22 · 10-14-2003, 11:45 AM

Quote:

Originally posted by Thai
patin,

1. As long as you don't lock the center diff, you can drive in 4wd all you want at any speed. (Note: Nissan Pathfinder's AWD system IS supposedly restricted to 55-65 mph...crappy system!) Once you are in 4wd, the system is FULL-TIME, just like in the Land Cruiser/new 4runner V8/Lexus. Therefore, i have never heard of such restriction.

2. If you lock your center diff, then it is advisable to do it on SLIPPERY surfaces. However, you can drive in a STRAIGHT line all you want. The only problem is when you start to make a turn...this can cause binding in the lock center diff...over time, this will wear out the center diff gearing and cause damage. Thus, you lock the center diff ONLY when off-roading where gear binding is minimized due to slippery surfaces (dirt, gravel, mud, etc.).

3. Once you lock the center diff, your VSC is turned OFF. The reason you still see lights flashing and weird noises is because 4-WHEEL TRACTION CONTROL (ATRAC) is still operating, braking the wheel(s) that are slipping.

The faster your rev your engine, the less traction control intervenes. For example, if you're gunning up a muddy hill, then you need to be more aggressive with the gas pedal. I think that ATRAC cuts down it's braking above 2500-3500 rpms. So, you can power up the muddy hill, with all wheels spinning. ATRAC is mostly for lower speeds.

Hope this helps.

Geez Thai, I thought I might get a little bit more *detailed* technical response??

That actually clears up a lot. I was paranoid all last winter about leaving it in 4WD over 55mph. I'm convinced that the guys at the dealership are not used to talking to people that are really interested in using their trucks the way they are able to be used. It's been tough getting anyone there to answer questions. I've asked several times about the 4WD system and the only thing they know is to not drive over 55 while it's engaged.

That makes sense about ATRAC still operating with the diff locked. This summer, I was in that very situation where I had to make it up a really slick hill to get back to the trail we were riding. I was fighting the traction control which I didn't feel comfortable about, but I had to get on it a little to make it. That's good to know it adjusts at higher RPMs.

Anyway, thanks for the info!

Thai · 10-22-2003, 05:05 PM

No problem.

Yeah, those Toyota salesman are useless. (To be fair, they also have to sell Corrollas, Prius, Camrys, etc.) I learned all this stuff from a lot of reading and trial-and-error. I wish they were more like the Land Rover salesman (who sales only SUVs), who at least knows something about off-roading.

Thai · 10-22-2003, 05:07 PM

FYI, the Hummer H1 (the real and ONLY Hummer) has Torsen T-2 system:

"Richard Fanco and Robert Gula of AM General talked about the development of the Hummer and described the 1999 civilian Hummer

Thai · 12-07-2003, 02:34 PM

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.

tundra_stl · 12-22-2003, 07:17 PM

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

Thai · 12-22-2003, 09:12 PM

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:

Difficulty with engaging 4wd??

Hope this helps.

tundra_stl · 12-23-2003, 12:08 PM

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.

Thai · 12-23-2003, 09:46 PM

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.

Thai · 01-01-2004, 02:50 AM

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

Thai · 01-01-2004, 02:50 AM

Minor correction from above owner's experience:

Locking the center diff turns OFF VSC and dethrottling function, but it does NOT turn off traction control. Traction control is ALWAYS on...on rear axle (in 2wd mode) or on both axles (in 4wd mode).

hillbilly · 01-07-2004, 03:25 PM

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).

Thai · 01-18-2004, 11:01 AM

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??

10-10-2003, 08:51 AM	#16 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	patin, 1. As long as you don't lock the center diff, you can drive in 4wd all you want at any speed. (Note: Nissan Pathfinder's AWD system IS supposedly restricted to 55-65 mph...crappy system!) Once you are in 4wd, the system is FULL-TIME, just like in the Land Cruiser/new 4runner V8/Lexus. Therefore, i have never heard of such restriction. 2. If you lock your center diff, then it is advisable to do it on SLIPPERY surfaces. However, you can drive in a STRAIGHT line all you want. The only problem is when you start to make a turn...this can cause binding in the lock center diff...over time, this will wear out the center diff gearing and cause damage. Thus, you lock the center diff ONLY when off-roading where gear binding is minimized due to slippery surfaces (dirt, gravel, mud, etc.). 3. Once you lock the center diff, your VSC is turned OFF. The reason you still see lights flashing and weird noises is because 4-WHEEL TRACTION CONTROL (ATRAC) is still operating, braking the wheel(s) that are slipping. The faster your rev your engine, the less traction control intervenes. For example, if you're gunning up a muddy hill, then you need to be more aggressive with the gas pedal. I think that ATRAC cuts down it's braking above 2500-3500 rpms. So, you can power up the muddy hill, with all wheels spinning. ATRAC is mostly for lower speeds. Hope this helps. __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

10-10-2003, 09:09 AM	#17 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	Torsen Center Differential: part 1 Link: TORSEN Traction Differential T-3 (Type 3 or Type C) TYPE 3 TRACTION DIFFERENTIAL Zexel Torsen's new generation T-3 Traction Differential are ideally suited for center applications, dividing torque front to rear in all-wheel drive vehicles. Similar to the T-2 parallel axis differential, the T-3 uses helical planetary gears which pilot on their outside diameter. The T-3, however, uses an extremely compact planetary gear configuration capable of nominal torque splits other than 50/50. The planetary nature of the design allows for a forward or rearward biased torque split. Unlike conventional speed sensing, limited-slip differentials, TORSEN T-3 is a full-time torque-sensing, torque biasing system. Torque and differentiation are continuously managed between the front and rear axles and biased instantaneously according to variable road conditions, automatically shifting the power to the wheel with the most traction before any wheel slip can occur. There are no clutches or preload to worry about, in fact, the TORSEN T-3's patented helical planetary gearing system is designed to PERFORM FOR THE LIFE OF THE VEHICLE. TORSEN T-3 Traction Differentials are available with a locking capability range of 20-30% and a nominal split from 65:35 and 35:65, front to rear. The T-3 can be designed to fit most transmissions or transaxles with no modifications required. In addition, it is fully compatible with ABS, Traction Control Systems, and Stability Control Systems, providing the ultimate traction management systems. __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

10-10-2003, 09:15 AM	#18 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	Torsen Center Differential: part 2 MULTIFUNCTION CAPABILITIES The TORSEN T-3 is an advanced, multi-function traction system providing continuous, uninterrupted torque output, splitting, biasing, and differentiation in one integral unit. It is always active, responding instantly to torque feedback from variable driving conditions. ENHANCED PERFORMANCE The TORSEN T-3's capability to immediately respond to variable driving conditions not only provides better traction, it also enhances the general performance of a vehicle. There is a marked improvement in total tractive effort as compared to open or speed-sensing center differential equipped vehicles. In addition, the exceptional efficiency of the T-3 allows the engine's torque to be used more effectively, delivering more horsepower to the road. The combined improvement in traction and the augmented power results in a nimble yet sure-footed vehicle that provides better handling, increased acceleration and an improved margin of safety. LOCKING EFFECT (FRICTION INTERFACE SURFACES) Side Gear Thrust to Housing Planet Gear Separation to Planet Carrier Planet Gear Thrust to Planet Carrier Helical Tooth Mesh Designed for today's modern all-wheel drive vehicles, the TORSEN T-3 Traction Differential is also suited for any application where a planetary differential is desired. TORSEN T-3 advantages include helical planetary gear design allowing front or rear biased asymmetrical torque splits under normal conditions. In addition, the number of planet gears can be increased or decreased, based upon system strength requirements. DESIGNED FOR HARD-TO-PACKAGE ALL-WHEEL DRIVE SYSTEMS The new generation TORSEN T-3 Traction Differential provides efficient torque splitting, biasing, and differentiation for improved vehicle performance. It is specifically engineered for hard to package all-wheel drive trains and is compatible with all automatic transmission fluids. The unique (patent pending) Twin Differential configuration makes the TORSEN T-3 especially well suited for front wheel drive based applications that relied on external-mounted torque-on-demand couplings to drive the rear axle. The Twin Differential offers the most compact all-wheel drive package with the greatest strength, while providing all the traction benefits of a TORSEN differential. With the TORSEN T-3, the vehicle has true all-wheel drive, driving all the wheels all the time. This can provide optimal traction management and deliver more power to the wheels, resulting in improved vehicle stability, handling, and performance. TORSEN T-3 IS AVAILABLE FOR ALL SPLIT AND LOCKING AFFECT REQUIREMENTS Zexel Torsen, Inc. will custom design, engineer, test, and manufacture the TORSEN T-3 Traction Differential to meet your specific torque split and locking affect requirements. Advanced TORSEN T-3 technology is a perfect match for applications with ABS, Traction Control, and stability control/vehicle dynamics systems, providing the ultimate traction control platforms for your vehicle. __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

10-22-2003, 05:05 PM	#20 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	No problem. Yeah, those Toyota salesman are useless. (To be fair, they also have to sell Corrollas, Prius, Camrys, etc.) I learned all this stuff from a lot of reading and trial-and-error. I wish they were more like the Land Rover salesman (who sales only SUVs), who at least knows something about off-roading. __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

10-22-2003, 05:07 PM	#21 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	FYI, the Hummer H1 (the real and ONLY Hummer) has Torsen T-2 system: "Richard Fanco and Robert Gula of AM General talked about the development of the Hummer and described the 1999 civilian Hummer __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"


Toyota 4Runner.org is the number one 4Runner community on the internet. Registered users don't see this ad. Register today!

12-07-2003, 02:34 PM	#22 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	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. __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

12-22-2003, 07:17 PM	#23 (permalink)
tundra_stl Member Join Date: Jan 2003 Location: St. Louis MO Posts: 47	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 __________________ 2003 4Runner SR5 4WD Galactic Grey,Leather Seats,Moon Roof,Rear Spoiler,16"Enkei Wheels,Grey Cladding .Love it,,Beautiful SUV!!!

12-22-2003, 09:12 PM	#24 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	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: Difficulty with engaging 4wd?? Hope this helps. __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

12-23-2003, 12:08 PM	#25 (permalink)
tundra_stl Member Join Date: Jan 2003 Location: St. Louis MO Posts: 47	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. __________________ 2003 4Runner SR5 4WD Galactic Grey,Leather Seats,Moon Roof,Rear Spoiler,16"Enkei Wheels,Grey Cladding .Love it,,Beautiful SUV!!!

12-23-2003, 09:46 PM	#26 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	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. __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

01-01-2004, 02:50 AM	#27 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	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 __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

01-01-2004, 02:50 AM	#28 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	Minor correction from above owner's experience: Locking the center diff turns OFF VSC and dethrottling function, but it does NOT turn off traction control. Traction control is ALWAYS on...on rear axle (in 2wd mode) or on both axles (in 4wd mode). __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

01-07-2004, 03:25 PM	#29 (permalink)
hillbilly Junior Member Join Date: Jan 2004 Location: Central PA Posts: 1	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). __________________ Black '01 SR5 4x4 w/ Black Pearl's: 1 Last edited by hillbilly; 01-07-2004 at 04:09 PM.

01-18-2004, 11:01 AM	#30 (permalink)
Thai Snowflake, Guns, & Texas! Join Date: Nov 2002 Location: Texas Posts: 11,905	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?? __________________ 2010 Toyota Prius V with ATP (daily driver) 2008 Toyota Sienna Salsa Red Pearl 2wd Limited (urban family "land cruiser") 2009 Acura TSX Palladium (wife's car) Off-roading Videos of My G I AM FAMOUS!! "Everyday is Halloween on the Internet"

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