Toyota 4WD review (3)

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Eugenio,77
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Feb 2004 - Sep 2020


Part 1. Initially FF models with automatic transmissions
Part 2. Initially FR models with automatic transmissions
Part 3. Initially FF models with manual transmissions


3.1. Full-time all wheel drive

3.1.1. Diff.Lock type

Full-time all wheel drive. Center differential - symmetrical, bevel gears (front/rear torque distribution 50/50), forced mechanical locking.

Pressing the "C.DIFF LOCK" button activates VSV which supplies a vacuum to the pneumatic actuator, which in turn shifts the differential lock control rod. If the rod has moved successfully and the differential is locked, the detect switch is on and the corresponding indicator on the combination meter lights up. In some cases, a pull-type switch was installed.




On the one hand, this is the only way to obtain 100% locking, on the other hand, it imposes a number of restrictions and requires driver's attention: it is not recommended to drive for more than hour or faster than 60 km/h with a locked differential, the lock cannot be activated directly during slipping...

This scheme was used on models without ABS, and gradually disappeared by the beginning of the 2000s.

ModelProductionTransmissionDifferential locking
Corolla/Sprinter 901987-1991E55F5+EF2Acenter - mechanical
Corolla/Sprinter 1001991-2002E55F5+EF2Acenter - mechanicalcenter - mechanical
Corolla/Sprinter 1101995-05.1997EF55F5+EF2Acenter - mechanical
Corolla 110 LHD1997-2001EF55F5+EF2Acenter - mechanical
Sprinter Carib 951990-1995E57F5+EF2Acenter - mechanical
Sprinter Carib 1101995-05.1996E55F5+EF2Acenter - mechanical
Carina 1701988-1992E55F5+EF2Acenter - mechanical
Corona 1701988-1992E55F5+EF2Acenter - mechanical
Camry/Vista 201988-1990E55F5+EF2Acenter - mechanical
RAV4 101994-2000E250Fcenter - mechanical, rear - Torsen (opt.)

Notes for the Carib community:

• On all JDM-models of the Corolla/Sprinter family (90-100-110), all-wheel drive was full-time - with a center differential (symmetrical bevel, torque distribution 50:50). Fundamental differences were in the methods of locking:
(1) Automatic transmission (1988-2002) - automatic locking by hydromechanical clutch (C.Diff Auto "with button", detailed description)
(2) Manual transmission without ABS (1988-1996) - forced mechanical hard-lock (C.Diff Lock)
(3) Manual transmission with ABS (1990-2002) - automatic "soft" lock by viscous coupling

• Do not confuse the center differential lock couplings of Corolla 90-100-110 with the rear drive V-Flex couplings of Corolla 120-140 and others

• Do not mistakenly accept the service sleeve with rods used on earlier models for the main differential lock mechanism. On models with a manual transmission and viscous coupling in the center diff, such a sleeve made it possible to choose three modes - the main operating mode, the service mode of the free differential (the viscous coupling is excluded from operation), the FWD service mode (rear-wheel drive is completely disabled). On models with automatic transmission, two modes were provided - the main operating mode and service modes of forced locking (hard-lock of the center differential, regardless of the hydromechanical coupling). Service modes can only be used for certain control operations in the workshop.

• For Sprinter Carib AE95 with manual transmission in 1988-1990 only C.DiffLock mechanical locking was provided (MT E57F5). In 1990, the optional ABS first appeared on the Corolla family cars - for some reason it could not interact with hard-lock, so versions with ABS began to be equipped with a viscous coupling in the center differential (MT E57F). Both versions were produced in parallel until 1995.

• For Sprinter Carib AE114..115 with manual transmission in 1995-1996, two options were provided - without ABS with mechanical forced locking (MT E55F5, E59F) or with ABS and viscous coupling (MT E55F, E59F). Then the presence of ABS became mandatory in Japan for all modifications, therefore, from May'1996 until 2002, only the viscous coupling version remained in production. LHD Corolla Wagon AE115 with manual transmission and 4WD was produced in 1997-2001 in both versions in parallel (E55F for versions with ABS, E55F5 for markets where ABS was not an obligatory equipment).

3.1.2. Visc type

Full-time all wheel drive. Center differential - symmetrical, bevel gears (front/rear torque distribution 50/50), locking - by viscous coupling.

Some later, with the implementation of ABS, the most common version appeared with auto-locking by a closed-type viscous coupling, similar to V-flex for AT/CVT models.

Viscous coupling simplified the design of the 4WD, but adversely affected off-road ability - due to the delayed response and the lack of full locking.



ModelProductionTransmissionDifferential locking
Corolla/Sprinter 901987-1991E55F,E59F+EF2AVcenter - viscous coupling
Corolla/Sprinter 1001991-2002E55F,E59F+EF2AVcenter - viscous coupling
Corolla/Sprinter 1101995-2000EF55F,E59F+EF2AVcenter - viscous coupling
Sprinter Carib 951990-1995E57F+EF2AVcenter - viscous coupling
Sprinter Carib 1101995-2002E55F,E59F+EF2AVcenter - viscous coupling
Carina 1701990-1992E55F+EF2AVcenter - viscous coupling
Carina 1901992-1996E56F,E57F+EF2AVcenter - viscous coupling
Carina 2101996-08.1998E56F,E57F+EF2AVcenter - viscous coupling
Corona 1701989-1992E55F+EF2AVcenter - viscous coupling
Corona 1901992-1996E56F,E57F+EF2AVcenter - viscous coupling
Corona 2101996-12.1997E56F,E57F+EF2AVcenter - viscous coupling
Caldina 1901992-2002E56F,E57F+EF2AVcenter - viscous coupling
Caldina 215W1997-2002E150Fcenter - viscous coupling, rear - Torsen
Carina ED 2051993-1998E56F+EF2AVcenter - viscous coupling
Corona Exiv 2051993-1998E56F+EF2AVcenter - viscous coupling
Celica 1851989-1993E150F,E151F,E152Fcenter - viscous coupling, rear - Torsen
Celica 2051993-1999E154Fcenter - viscous coupling, rear - Torsen
Camry/Vista 201988-1990E56F2+EF2AVcenter - viscous coupling
Camry/Vista 301990-1994E56F2+EF2AVcenter - viscous coupling
Camry/Vista 401994-1998E59F+EF2AVcenter - viscous coupling
RAV4 202000-2005E352Fcenter - viscous coupling, rear - Torsen (opt.)



3.2. Selectable all wheel drive

3.2.1.1. Flex type


Basic front-wheel drive, no center differential, the rear wheels are connected via viscous-friction coupling.

RBC coupling connects the two parts of the intermediate propeller shaft and operates when a significant slip of the front wheels occurs, at other times the car remains front-wheel drive.

For details - "Toyota AWD. V-Flex".

ModelProductionTransmission
Starlet 80,901989-1999C50F + CF1A
Tercel 40,501990-1999C50F + CF1A
Vitz/Platz 10,201999-2005C50F + CF1A

3.2.1.2. V-Flex I type

Basic front-wheel drive, no center differential, the rear wheels are connected via viscous coupling.

The viscous coupling connects the two parts of the intermediate propeller shaft and operates when a significant slip of the front wheels occurs, at other times the car remains front-wheel drive.

ModelProductionTransmission
Probox/Succeed 502002-2014C50F + CF1A

3.2.2. V-Flex II type


Basic front-wheel drive, no center differential, the rear wheels are connected via viscous coupling.

The coupling filled with silicone fluid, connects the propeller shaft to the input shaft of the rear differential and operates when a significant slip of the front wheels occurs, at other times the car remains front-wheel drive.

ModelProductionTransmission
Carina 21008.1998-2001S55F+EF2A
Corona 21012.1997-2001S55F+EF2A
Caldina 215G1997-2002S55F+EF2A, rear diff. - Torsen (GT)

3.2.3. ATC type


Basic front-wheel drive, no center differential, the rear wheels are connected via multi-plate electromechanical coupling.

The coupling connects the propeller shaft to the input shaft of the rear differential. In most cases, the car remains front-wheel drive, but if necessary, the control system automatically maintains the target value of torque transmitted to the rear wheels (for details, "ATC coupling").
ModelProductionTransmission
RAV4 302006-2012E352F,E359F,EA64F,EB61F
RAV4 402012-2019EB61F, EA64F
RAV4 502019-..EG62F
Urban Cruiser 1102009-2014EC65F

3.2.3.1. GR-FOUR (Active Torque Split)

Basic front-wheel drive, no center differential, the rear wheels are connected via multi-plate electromechanical coupling. Optional rear and front Torsen differentials. The drive mode dial switch sets the maximum clutch lock grade.

So patheticaly presented new "Active Torque Split", supposedly providing a wide range of the torque distribution between the axles, turned out to be a mystification.


In fact, everything is quite primitive - the ATC coupling plus the gear ratios in the drive of the front and rear wheels differ by 0.7% (in the transfer teeth ratio is 17:39, in the rear differential - 41:18). When the coupling is almost locked, the rear wheels to tend to rotate faster than the front ones, creating the effect of a mechanical differential with unequal distribution of torque. Of course, all the ratios mentioned in the press-releases (100:0, 60:40, 30:70, 20:80, 0:100) are purely hypothetical, arbitrarily arising at a certain time and under certain conditions of wheel traction.

And what about "innovation", a similar scheme with different gear ratios appeared on the 2015 Ford Focus RS, and the principle itself has existed at least since the days of American SUV in the 1970s.

ModelProductionTransmission
GR Yaris2020-..EA67F + GF1A













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