Feb 2004 - Nov 2015
Part 1. Initially FF models with automatic transmissions
Part 2. Initially FR models with automatic transmissions
Full-time four wheel drive, with a symmetrical center differential, locking by hydromechanical clutch
The good old full-time, used for initially FF models, was really "full" and "permanent", with three differentials (center, front, rear) and symmetrical 50:50 torque distribution between the front and rear wheels.
Corolla (90..110), Corona (190..210), Vista-Camry (20..40), RAV4 (10) families was applied with multi-plate hydromechanical clutch for center differential locking.
Pressing "C.DIFF AUTO" button permits control unit to select the locking rate depending on the driving conditions, when button is not pressed center differential continuously free. As A241H gearbox based on gearbox with simple hydraulic control, its locking principles are less progressive (detailed description - "A241H automatic transmission"), whereas A540H has реализовано real electronic control with feedback (detailed description - "A540H automatic transmission").
Stananrd for everyday driving is the automatic mode, so disabling it is provided only for towing or using the undersized spare wheel. The maximum locking rate is realized at selector lever position "L" and "R" (manual).
Since 1994 models with A540H had not "C.DIFF AUTO" button - the driver is completely removed from the locking control and automatic mode activated permanently.
It should be noted that STD I is the most advanced, reliable and efficient among all the variations of Toyota all-wheel drive for initially FF cars. Unfortunately, no such models were produced since 2002.
|Caldina 190||1992-2002||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Carina 190||1992-1996||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Carina 210||1996-08.1998||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Carina ED 200||1993-1998||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Corolla / Sprinter 90||1987-1992||A241H||center - hydromechanical clutch|
|Corolla / Sprinter 100||1992-2002||A241H||center - hydromechanical clutch|
|Corolla / Sprinter 110||1995-2000||A241H||center - hydromechanical clutch|
|Corolla Spacio 110||1997-2002||A241H||center - hydromechanical clutch|
|Corona 190||1992-1996||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Corona 210||1996-12.1997||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Corona Exiv 200||1993-1998||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Ipsum 10||1996-04.1998||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|RAV4 10||1994-2000||A540H+AF2BE||center - electronically controlled hydromechanical clutch, rear - Torsen (opt.)|
|Sprinter Carib 95||1988-1995||A241H||center - hydromechanical clutch|
|Sprinter Carib 110||1995-2002||A241H||center - hydromechanical clutch|
|Vista / Camry 20||1988-1990||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Vista / Camry 30||1990-1994||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
|Vista / Camry 40||1994-1998||A540H+AF2BE||center - electronically controlled hydromechanical clutch|
Full-time four wheel drive, with a symmetrical center differential, locking by viscous coupling
At the second half of 1990s Toyota turned to new transmission types and more primitive solutions, so STD II obtained viscous coupling for the center differential locking. Design simplifying did not improve the reliability, but greatly worsened performance - due to too low viscous coupling efficiency compared to hydromechanical.
Combined front and center differentials with viscous coupling was used by Toyota previously - at models with manual gearbox. New scheme follows the same principle, only visible difference is five instead of four satellites in center differential.
The rear differential could be either free/open, or LSD Torsen (option).
Note. In technical English all "self-locking"/"limited slip differentials" called "LSD". However, they are divided into viscous (with "closed" viscous coupling filled with silicone liquid), friction (the disks and plates operates in differential fluid), Torsen etc.
|Alphard 10||2002-2008||U140F+MF2AV||center - viscous coupling, rear - Torsen (opt.)
|Caldina 215W GTT||1997-2002||U140F+MF2AV||center - viscous coupling|
|Caldina 246 GT4||2002-2007||U140F+MF2AV||center - viscous coupling, rear - Torsen (opt.)
|Harrier 10||1997-2003||U140F+MF2AV||center - viscous coupling, rear - Torsen (opt.)
|center - viscous coupling, rear - Torsen (opt.)
|Highlander 20||2000-2003||U140F+MF2AV||center - viscous coupling, rear - Torsen (opt.)|
|Kluger||2000-2007||U140F+MF2AV||center - viscous coupling, rear - Torsen (opt.)|
|Lexus RX MCU3#||1998-2003||U140F+MF2AV||center - viscous coupling, rear - Torsen (opt.)|
|Lexus RX350 GSU3#||2006-2008||U151F+MF2AV||center - viscous coupling|
|RAV4 20||2000-2006||U140F+MF2AV||center - viscous coupling, rear - Torsen (opt.)|
Basic front-wheel drive, no center differential, the rear wheels are connected via viscous coupling
Since 1997 many Toyota's models obtain the new four-wheel drive known as "V-Flex Fulltime 4WD". It's not true "fulltime" - actuallly it is just auto-connected rear axle (rear wheels). Center differential was eliminated, and the torque through transfer (or, simply, bevel gearbox) is drive by propeller shaft to back. Before the rear differential the viscous coupling mounted, which connects the propeller shaft and the input shaft of rear differential only when front wheels slipping (V-Flex II). In the other cases the car remains front-wheel-drive.
B-class models (Starlet, Tercel, first Vitz families) had the such scheme of simplified all-wheel drive previously (since 1990), the main difference - viscous coupling not installed on the rear axle but connects the two parts of the propeller shaft (V-Flex I).
- viscous coupling tardy "triggering"
- full locking inability
- potential danger when aggressive driving
- low durability and reliability of the viscous coupling
|Probox / Succeed 50||2002-2014||U340F|
|Probox / Succeed 160||2014-..||K310F|
|Tercel / Corsa / Corolla II 40||1990-1994||A244F+CF1A|
|Tercel / Corsa / Corolla II 50||1994-1999||A244F+CF1A|
|Camry / Camry Gracia / Mark II Qualis V20||1997-2001||A541F|
|Corolla / Fielder / Runx / Allex 120||2000-2006||U340F,U341F+MF1A|
|Corolla Axio / Fielder 140||2006-2012||K310F, K311F|
|Corolla Spacio 120||2001-2007||U341F|
|Premio / Allion 240||2001-2007||U341F+MF1A|
|Premio / Allion 260||2007-..||K311F|
Basic front-wheel drive, no center differential, the rear wheels are connected via electromechanical coupling
ATC (Active Torque Control) is used by Toyota since 1998, similar to the V-Flex, but the rear wheels connection performs by electromechanical coupling instead viscous. The control system automatically maintains the target value of torque transmitted to the rear wheels ("ATC coupling"). After 2012 at some models the system received the designation "DTC" (Dynamic Torque Control).
Since active implementation of vehicle stability systems (for Japanese brands - from the second half of the 2000s) and the appearance of differential locking emulation via brake system, the new phase of all-wheel drive started. At some manufacturer's models communication of torque-on-demand 4WD and ESP can provide a greater effect than even classic full-time with only center locking, unable to overcome "diagonal". However, comparing the operation of different modern suv at light off-road, we have to admit - effectiveness of Toyota's ATC 4WD and locking emulation are among the worst.
- quick overheating and disconnection of coupling under load
- low efficiency
- bearings wear ("ATC coupling repair").
system have few variants of control:
• With "AUTO" button (passenger cars and minivans) - operation modes "AUTO 4WD" and "2WD". At OFF state there is only front-wheel- drive, at ON state - control unit automatically manage torque distribution to the rear wheels.
• With "LOCK" button (light suvs) - operation modes "AUTO 4WD" и "LOCK". In AUTO mode control unit automatically manage torque distribution to the rear wheels, at LOCK mode - maintains the highest possible rate of electromechanical coupling locking.
• Without control buttons (some Japan domestic models) - constant automatic control of torque distribution.
|Alphard / Vellfire 20||2008-2015||U660F|
|Alphard / Vellfire 30||2015-..||K115F|
|Corolla Axio / Fielder 160||2012-..||K310F|
|Corolla Rumion 150|| 2007-..||K311F|
|Lexus RX GGL15||2008-2015||U660F|
|Lexus RX L20||2015-..||-|
|Mark X Zio||2007-2013||K112F|
|Noah / Voxy 60||2001-2007||K111F,A248F|
|Noah / Voxy 70||2007-2014||K111F|
|Noah / Voxy / Esquire 80||2014-..||K114F|
|Porte / Spade 140||2012-..||K310F|
|RAV4 / Vanguard 30||2006-..||K111F,K112F,U151F,U660F|
|Venza 10||2008-..||U660F, U760F|
Full-time four-wheel drive, symmetrical center differential, differential locking emulation via brakes
VSC+ is a variation of the STD II scheme without any couplings. Instead, the locking emulation is performed using the ABS/TRC/VSC - slipping wheel is braked, thus torque at the other wheel of same axle is increased. Similarly, the torque is redistributed between the front and rear wheels. The effectiveness of this scheme is really pour even at not severe conditions.
|Lexus RX MCU35||2003-2006||U140F'+MF2A|
: TM - transmission (gearbox, CVT), TR - transfer, FD - front differential, RD - rear differential, CD - center differential, CDC - hydraulic clutch, VC - viscous coupling, EC - electromechanic coupling.
Более 2000 руководств
по ремонту и техническому обслуживанию
автомобилей различных марок