Thanks for the info. I think I recognize that acronym. Is this the same system from the 2002, that uses the brakes to mitigate wheel slippage? Thanks again in advance.
The Sequoia has an open center differential. This makes it slightly less capable off road. While the torsen can bias power front to rear, it always leaves some power in both ends. With the open center of the Sequoia (and 2002 Runner) all available power will be sent to one end or the other.
In all honesty, I am a bit confused by this as well. Until Toyota came out with the new Torsen center, I had been told that power remained roughly 50/50. It was explained to me that a left front spinning wheels had the brakes applied which fooled the front differential into sending power to the right, thereby not affecting front to rear power transfer. If both front wheels lost traction, then 100% of the power would be diverted to the rear due to the braking action on those wheels.
With the advent of the new Torsen system on the same A-Trac system, the story I am getting is changing slightly. Our training manager told us that it was fairly easy to alter the front/rear power split. I'm not sure this guy knew exactly what he was talking about though. Unfortunately, finding a factory guy who can explain this stuff and is available to the dealer level to answer such questions is not easy.
Bottom line for me is that when in 4WD in the 2002, you have an extremely capable vehicle. There is VERY little it can't handle. The 2003 is even better with even fewer situations it can't handle. Personally, I'd love either version in my Tundra.
Thanks for your answers! That was what i thought. If you think YOU have it hard, it is nearly impossible for me to get ANY technical answers as a customer! I am just glad that this board has someone like you...who knows something about Toyota SUVs!
Maybe the Torsen allows for more consistent, faster, & smoother shifting of power front to rear because Torsen has a set of programs to distribute power under certain conditions (70/30, 30/70, 50/50, etc.).
I never could get why ATRAC and stability control are not on trucks. Maybe the rear end is too light and therefore would turn the system on too often?? Anyway, truck is where these systems are needed MOST! Trucks are notorious for sliding sideways and losing traction on wet surfaces. They need it much more than sports cars!
I think I know the reason we don't have this on trucks. Actually it is two reasons:
1. Cost. The Tundra and Tacoma are already pretty expensive. Adding something like this would certainly add to their prices in an already competitive market. Until the 2003 MY, ABS was an option but now that they have it standard, the upgrade would not be as bad.
2. Consumer distrust. Pickup truck buyers are generally not as motivated by technology as SUV buyers. They tend to want it simple and easy to understand and function like every other truck they have ever owned.
Those are my theories. I don't like either one but I'm sticking to them. I for one would love a Torsen center on my Tundra.
I am very happy that Toyota has VSC & ATRAC on the 4Runners. That was one of my top priorities when i shopped for my SUV...right there, '02 Pathfinder and Jeep GC are out of the picture.
Hi all, This past weekend, a friend of mine told me that I could install a rear locker on my 2002 2wd 4runner? Any truth behind this? What's the point in putting a locker on a 2wd?
Yes, it can be done. However, i believe you need to know a lot about wiring and may need to modify the rear axle housing. It is not easy to do. I have heard one person doing it successfully.
A locker will help traction on slippery or rough terrain (like off-roading). I would not use it on dry land, not even in light rain.
Locking differentials are available, but a locking differential is best left strictly as an offroad mod. This splits torque 50-50 between axles and will lock both wheels into rotating at the same speed. A vehicle with a conventional open differential transfers torque to the wheel with least resistance (i.e. the free spinning wheel). Driving a locker on the street will undoubtebly cause premature axle/differential failure and harsh driving conditions. A limited slip differential allows the wheels to slip slightly when making turns yet provides additional traction in low traction situations. If you need more traction than this, you might be better served finding a 4wd vehicle. Lots has been written about this - so do a little research before jumping into a project like this.
CLIFFY, up to what mph can you shift this system into 4WD? I know some of the old systems were limited to 55mph, but they didn't have an open or Torsen center diff in them.
What if the button (to lock the center diff) gets accidently pushed by a kid playing in the car when it is off? What if you accidently bumped it when the car was on, is there a warning????
The "center diff lock" button is electronic. You can only lock it when you are in 4wd (HI and LO). When it is pressed, the 4wd graphic will blink. Yes, if you are in 4wd, you can accidentally press the lock button. However, it is pretty hard to accidentally press it because it is on the dash left of the steering wheel. Unless, you have REALLY long legs, you knees will not come close to it. If the 4runner is off, pressing it will do nothing...it is electronic. When you turn the car back on, it is still unlock.
Thanks for replying. No need to worry about me doing that mod. I was just surprised that it could be done and is avaliable to 2wd truck. I thought my friend was joking me around. So far, the ranch roads and fire roads have posed no problem for me.
Intmed99 answered your question correctly, but I also want to make sure you understand that while the engagement speed is 62, once it is engaged, you can drive any speed you want.
I haven't a clue. I suspect it is 62, but I don't know that for sure. I do know that it sometimes can be a trick to disengage it if you don't know the secret. If you are coasting down hill, tap the brakes. If you are accelerating up a hill, quickly remove your foot from the gas and then hit it again. You need to interrupt whatever the drive train is doing before it will cut off.
This may explain why they switch to Torsen in the '03 4runner...better on-road manners:
The new torque-sensing feature allows the torque split mid-point to be more biased toward the rear, sending more torque to the rear wheels, providing better stability control whether the driver is accelerating at high or low speeds. The static rear-drive bias favors stable tracking on- or off-road, decelerating or accelerating. The Torsen™ type sensing provides three dynamic torque split ratios, depending on the available traction on the vehicle at the time. A static torque split favors the rear with a 40/60 percent front-to-rear split. When the front wheels slip, up to 71 percent of the split ratio goes to the rear wheels. When the rear wheels slip, up to 53 percent of the split is applied to the front wheels.
Isn't the real difference within the center diff'l? If T/L can package a center diff'l, a front diff'l, and a VC all within the same "case" in the HL and RX, why couldn't a 3-mode torsion diff'l go in there?
I'd even settle for a 2-mode diff'l, like the old Aerostar, 30/70 F/R until slippage and then 50/50.
Were starting to get into an area that I am not fully comfortable with my knowledge so bear with me. The RX has a transaxle and technically, not a transmission (I am sure of that much). The method by which a rear drive shaft is connected and operated can't be the same as a primarily RWD vehicle like the Aerostar/4Runner/LC/etc. I am just not sure it is possible to accomplish a true 4WD system (no VC) with a transverse mounted engine. If you know of one, I'd like to know.
The Porsche 968 has a transaxle and is RWD, so I don't see that a transaxle vs a transmission enters into the equation.
On the other hand I'm also beyond my depth since I haven't a clue as to why or how the HL and the RX manage to bias the torque toward the front so severely when both ends are directly driven from separate outputs of the center (open) diff'l.
I believe that the Mazda Tribute and its Ford counterpart have traversely mounted engines and are (incorrectly) marketed as AWD and 4WD.
They seem to have adopted the Aerostar method, it's basically FWD with an "automatic" AWD mode which engages the rear drive only if the front is slipping and a mode wherein it can be locked into 4WD (part-time) only on low traction surfaces.
Wasn't the 2WD version of the Aerostar a longitudinally mounted engine and RWD? I'm almost certain it was because I recall people lamenting its passing because the RWD van was pretty good for towing. If that is the case, I would suspect that it was not a FWD until slip was detected.
The AWD aerostar had/has native/normal torque distribution of 30/70 F/R and if the rear slipped then electronically switched to 50/50. Then after a time if no further slippage occurred it would revert to 30/70.
Suspect it had a torsen center diff'l very much like the new 4runner except only two modes.
Can any one definitely say how the torsen operates? Is it related to a viscous coupling? Clutches, wet or dry? Gearing, if so how does the gearing "know" how to engage/disengage?
Just stopped by the Toyota store to look at the 03 4runner and pick up a sales brochure. I'll take back any statements I have made about the 4runner vs the HL or RX, the 4runner is just plain too damn big and bulky.
But.
From the brochure on the TORSEN limited slip diff'l:
"For example, when the vehicle is traveling straight, 40% of the torque is distributed to the front wheels, while 60% is allocated to the rear (40/60), providing the driver with a feel typical of a rear-wheel drive vehicle."
WHEN THE VEHICLE IS TRAVELING STRAIGHT ????
Is it entirely possible that Toyota has figured out how to design a truly excellent AWD vehicle?
The statement implies that the torque to the front wheels might be something other than 40% if the vehicle is turning. I have always firmly believed that it is wrong to have driving, motive, force to the front wheels while turning.
Motive forces, acceleration or deceleration, to the front wheels should be reduced altogether when turning, or as a function of the level of need from tractive adhesion to be allocated to directional control.
Maybe, we can hope, Toyota has arrived at the perfect AWD solution.
40/60 normal, 29/71 w/front slippage, 53/47 w/rear slippage, AND 29/71 (5/95 severe turn??) when turning.
Now, can I have an RX with this feature next spring?
"Can any one definitely say how the torsen operates? Is it related to a viscous coupling? Clutches, wet or dry? Gearing, if so how does the gearing "know" how to engage/disengage?"
"My guess would be electronically, electrically actuated clutches, like the Ford Aerostar."
Er, no need to guess on an important question. It's sort of like guessing that the X5 has bi-xenons.
A simple search on the Internet will provide something like:
Hope you find the article useful, or find other articles easily searched for. Torsen is purely mechanical, it does not rely on locks or clutches or viscuous fluid.
Steve, My spouse and I are having a disagreement about the center diff button. I read in one post where you should Never push the button on hard pavement, but he says it is OK as long as it is flat, even pavement. Will you clarify? Or point me somewhere in which you have clarified this before. I sure don't want to screw something up on our new 2003........
Gear-based is fine, I have no doubt that that's how it senses traction disparities and adjusts torque distribution.
But the 4runner seems to have three torsen modes which to me means something outside the torsen "box" itself is switching from one mode to another. That's what the Aerostar did with an electric clutch. The Aerostar simply detected F/R driveline rotational disparity and automatically actuated the 50/50 mode.
Apparently the 4runner is normally in 40/60 mode and automatically goes to 29/71 with front slippage (only) or 53/47 mode with rear slippage (only). The way I read it there is a distinct possibility it decreases the engine driving/braking torque to the front driveline as the VSC ecu "senses" the need for the front tires' roadbed adhesion coefficient be dedicated to directional forces.
I don't think any torsen gear-based "box" can do any of that of itself.
With regard to bi-xenons the BMW site actually said it had them and I already apologized for believing what BMW published as factual.
I know I answered you by e-mail, but allow me to respond here as well for the benefit of others. No, you should not lock the center differential on dry pavement. If you are driving in a straight line, you will not hurt it, but there is no need to do this. On older part time systems, you did need to engage the 4WD system every month or so to keep the internal parts lubricated. This is not required on the new ones because they are already in 4WD all the time anyway. The center differential lock does nothing more than prevent the Torsen differential from shifting power front to rear.
Wwest - the reason Toyota specifies the Torsen split in a straight line is that when a vehicle is turning, the rear wheels describe a smaller arc than the fronts. As a result, the shafts to the front and rear diffs spin at different speeds and any torque split scheme based thereon will change the torque to each shaft.
The Torsen diff uses an interesting setup of worm gear and side gears. The driving principle is that a worm gear can turn a conventional gear, but reverse the torque and the gears cannot turn the worm gear due to a lack of leverage. They work great in racing, but for offroading where tires frequently spin and go airborne (zero traction) seem to need the back up of a traction control system or they spin helplessly.
On the transaxle comment. A transaxle is merely a transmission and axle built into one assembly. It is common on laterally mounted engines (most) and there's no reason save limited space that a true 4WD system could not be engineered with this setup. Porsche uses this setup (originally called the Weissach Axle) for weight distribution, but most manufacturers of mass produced FWD vehicles use it for low cost and space efficiency.
I don't have any question about the need for "give", slack, side to side or front to back.
The 03 4runner note seems to imply that the torque distribution when driving straight is different from when turning, say a tight turn under serious throttle.
Were I given the responsibility to design the perfect AWD system it would be one wherein I monitored the yaw sensor (accelerometer) for centrifical force level and the steering wheel position sensor and decreased the engine drive/decel torque to the front wheels accordingly.
I remain hopeful that this is what Toyota has done with the 03 4runner and further hopeful that the technique will soon be ported to the RX. Unless the MDX gets there first.
I believe there have been several systems available that do use these sensors to optimize AWD power distribution. I have a buddy with an '02 BMW Xi and it is able to vary things constantly based on lateral acceleration, steering wheel angle, vehicle speed, shaft speed differences, etc. Over 10 years ago, Porsche also used these inputs on the mighty AWD 959 to vary torque split to each wheel.
On your 4Runner note - yes, it is different. As previously stated, when a vehicle turns the correct torque split would be different than the straight line split. So Toyota is only stating what the straight line split is since the split varies depending on the turn.
When turning the front tires travel a greater distance than the rear, rotate faster than the rear. Therefore if the straightline torque split is 29/71, then with the front wheels appearing to slip more torque would be allocated to the rear.
Appreciate any advice. I'm looking at the '02 or '03 Tacomas. As I live in Minnesota, I've limited my search to the 4x4 models. However, I understand the TRD accessories on the 4x2 PreRunner offer some off-road traction features which may help in driving on snow- or ice-covered roads.
Do I stay with the 4x4 models or consider the PreRunner with TRD?
If you live in MN, don't get the PreRunner. You can get that model with a locking rear end but that will only help you start moving. It wont help in normal driving.
Definitely don't get the 2WD for MN. A rear locker on snowy or icy roads is actually far more dangerous than an unlocked rear locker. If you induce wheelspin with the locker, both wheels are loose and the truck will easily spin. Without the locker, at least you'll tend to spin only one wheel while the other rolls and helps prevent a dangerous spin. I have had lockers on several rigs and live in a snowy environment.
To get around in MN, I'd definitely get a 4WD - particularly in a light rear ended pickup. Having said this, I believe you can get a TRD 4WD pickup with a rear locker, no?
Comments
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
Both V6 and V8 have Torsen.
Does it go to the front (slipping) axle or does it go to the rear (traction) axle??
Or does it stay at 50/50??
Thanks.
With the advent of the new Torsen system on the same A-Trac system, the story I am getting is changing slightly. Our training manager told us that it was fairly easy to alter the front/rear power split. I'm not sure this guy knew exactly what he was talking about though. Unfortunately, finding a factory guy who can explain this stuff and is available to the dealer level to answer such questions is not easy.
Bottom line for me is that when in 4WD in the 2002, you have an extremely capable vehicle. There is VERY little it can't handle. The 2003 is even better with even fewer situations it can't handle. Personally, I'd love either version in my Tundra.
Maybe the Torsen allows for more consistent, faster, & smoother shifting of power front to rear because Torsen has a set of programs to distribute power under certain conditions (70/30, 30/70, 50/50, etc.).
I never could get why ATRAC and stability control are not on trucks. Maybe the rear end is too light and therefore would turn the system on too often?? Anyway, truck is where these systems are needed MOST! Trucks are notorious for sliding sideways and losing traction on wet surfaces. They need it much more than sports cars!
1. Cost. The Tundra and Tacoma are already pretty expensive. Adding something like this would certainly add to their prices in an already competitive market. Until the 2003 MY, ABS was an option but now that they have it standard, the upgrade would not be as bad.
2. Consumer distrust. Pickup truck buyers are generally not as motivated by technology as SUV buyers. They tend to want it simple and easy to understand and function like every other truck they have ever owned.
Those are my theories. I don't like either one but I'm sticking to them. I for one would love a Torsen center on my Tundra.
This past weekend, a friend of mine told me that I could install a rear locker on my 2002 2wd 4runner? Any truth behind this? What's the point in putting a locker on a 2wd?
Thanks.
A locker will help traction on slippery or rough terrain (like off-roading). I would not use it on dry land, not even in light rain.
The new torque-sensing feature allows the torque split mid-point to be more biased toward the rear, sending more torque to the rear wheels, providing better stability control whether the driver is accelerating at high or low speeds. The static rear-drive bias favors stable tracking on- or off-road, decelerating or accelerating. The Torsen™ type sensing provides three dynamic torque split ratios, depending on the available traction on the vehicle at the time. A static torque split favors the rear with a 40/60 percent front-to-rear split. When the front wheels slip, up to 71 percent of the split ratio goes to the rear wheels. When the rear wheels slip, up to 53 percent of the split is applied to the front wheels.
I'd even settle for a 2-mode diff'l, like the old Aerostar, 30/70 F/R until slippage and then 50/50.
The Porsche 968 has a transaxle and is RWD, so I don't see that a transaxle vs a transmission enters into the equation.
On the other hand I'm also beyond my depth since I haven't a clue as to why or how the HL and the RX manage to bias the torque toward the front so severely when both ends are directly driven from separate outputs of the center (open) diff'l.
I believe that the Mazda Tribute and its Ford counterpart have traversely mounted engines and are (incorrectly) marketed as AWD and 4WD.
They seem to have adopted the Aerostar method, it's basically FWD with an "automatic" AWD mode which engages the rear drive only if the front is slipping and a mode wherein it can be locked into 4WD (part-time) only on low traction surfaces.
Suspect it had a torsen center diff'l very much like the new 4runner except only two modes.
Just stopped by the Toyota store to look at the 03 4runner and pick up a sales brochure. I'll take back any statements I have made about the 4runner vs the HL or RX, the 4runner is just plain too damn big and bulky.
But.
From the brochure on the TORSEN limited slip diff'l:
"For example, when the vehicle is traveling straight, 40% of the torque is distributed to the front wheels, while 60% is allocated to the rear (40/60), providing the driver with a feel typical of a rear-wheel drive vehicle."
WHEN THE VEHICLE IS TRAVELING STRAIGHT ????
Is it entirely possible that Toyota has figured out how to design a truly excellent AWD vehicle?
The statement implies that the torque to the front wheels might be something other than 40% if the vehicle is turning. I have always firmly believed that it is wrong to have driving, motive, force to the front wheels while turning.
Motive forces, acceleration or deceleration, to the front wheels should be reduced altogether when turning, or as a function of the level of need from tractive adhesion to be allocated to directional control.
Maybe, we can hope, Toyota has arrived at the perfect AWD solution.
40/60 normal, 29/71 w/front slippage, 53/47 w/rear slippage, AND 29/71 (5/95 severe turn??) when turning.
Now, can I have an RX with this feature next spring?
Or even an HL??
"My guess would be electronically, electrically actuated clutches, like the Ford Aerostar."
Er, no need to guess on an important question. It's sort of like guessing that the X5 has bi-xenons.
A simple search on the Internet will provide something like:
http://www.howstuffworks.com/differential8.htm
Hope you find the article useful, or find other articles easily searched for. Torsen is purely mechanical, it does not rely on locks or clutches or viscuous fluid.
But the 4runner seems to have three torsen modes which to me means something outside the torsen "box" itself is switching from one mode to another. That's what the Aerostar did with an electric clutch. The Aerostar simply detected F/R driveline rotational disparity and automatically actuated the 50/50 mode.
Apparently the 4runner is normally in 40/60 mode and automatically goes to 29/71 with front slippage (only) or 53/47 mode with rear slippage (only). The way I read it there is a distinct possibility it decreases the engine driving/braking torque to the front driveline as the VSC ecu "senses" the need for the front tires' roadbed adhesion coefficient be dedicated to directional forces.
I don't think any torsen gear-based "box" can do any of that of itself.
With regard to bi-xenons the BMW site actually said it had them and I already apologized for believing what BMW published as factual.
The Torsen diff uses an interesting setup of worm gear and side gears. The driving principle is that a worm gear can turn a conventional gear, but reverse the torque and the gears cannot turn the worm gear due to a lack of leverage. They work great in racing, but for offroading where tires frequently spin and go airborne (zero traction) seem to need the back up of a traction control system or they spin helplessly.
On the transaxle comment. A transaxle is merely a transmission and axle built into one assembly. It is common on laterally mounted engines (most) and there's no reason save limited space that a true 4WD system could not be engineered with this setup. Porsche uses this setup (originally called the Weissach Axle) for weight distribution, but most manufacturers of mass produced FWD vehicles use it for low cost and space efficiency.
IdahoDoug
The 03 4runner note seems to imply that the torque distribution when driving straight is different from when turning, say a tight turn under serious throttle.
Were I given the responsibility to design the perfect AWD system it would be one wherein I monitored the yaw sensor (accelerometer) for centrifical force level and the steering wheel position sensor and decreased the engine drive/decel torque to the front wheels accordingly.
I remain hopeful that this is what Toyota has done with the 03 4runner and further hopeful that the technique will soon be ported to the RX. Unless the MDX gets there first.
I believe there have been several systems available that do use these sensors to optimize AWD power distribution. I have a buddy with an '02 BMW Xi and it is able to vary things constantly based on lateral acceleration, steering wheel angle, vehicle speed, shaft speed differences, etc. Over 10 years ago, Porsche also used these inputs on the mighty AWD 959 to vary torque split to each wheel.
On your 4Runner note - yes, it is different. As previously stated, when a vehicle turns the correct torque split would be different than the straight line split. So Toyota is only stating what the straight line split is since the split varies depending on the turn.
IdahoDoug
When turning the front tires travel a greater distance than the rear, rotate faster than the rear. Therefore if the straightline torque split is 29/71, then with the front wheels appearing to slip more torque would be allocated to the rear.
Right?
Do I stay with the 4x4 models or consider the PreRunner with TRD?
To get around in MN, I'd definitely get a 4WD - particularly in a light rear ended pickup. Having said this, I believe you can get a TRD 4WD pickup with a rear locker, no?
IdahoDoug