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Toyota 4WD review (2)

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Eugenio,77
mail@toyota-club.net

© Toyota-Club.Net
Feb 2004 - Nov 2015


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

2.1. Part-Time - Hub type
Basic rear-wheel drive, no center differential, front wheels are mechanically connected

One of the simplest types of all-wheel drive - with forced connection of front axle. Transfer have a reduction gear (planetary) for heavy-duty conditions, that operates in 4WD mode.



Transfer is controlled by lever, front drive shafts are connected to wheels with mechanical freewheel hubs (manual switching).

At the second variant used electric hubs and actuators at transfer.

"+" Relative simplicity, reduction gear availability.
"-" 4WD mode can be used on slippery surfaces only (rain, ice, snow). Otherwise, noise increasing, fuel consumption increasing, steering control deteriorates, and most importantly - highly worn tires and the transmission components. Mechanical hubs are quite reliable, but not easy-to-use, electrical - not so reliable.

Shift order:
2WD→4WD - at speed below 80 km/h with accelerator released, not engage during slipping (only after a full stop).
4WD→2WD - - at any speed.
4WD-H→4WD-L - when the vehicle is stationary and at "N" range of transmission.
4WD-L→4WD-H - when the vehicle is stationary and at "N" range of transmission.

ModelProductionTransmissionDifferential locking
4Runner 1851995-2000A340Frear - mechanical (opt.)
HiAce H10#..12#1989-1995A45DF,A340F + HF1Arear - LSD (opt.)
LiteAce/TownAce 301992-1996A45DF + HF1Arear - LSD (opt.)
Tacoma 160-1701995-2000A340Frear - mechanical (opt.)


2.2. Part-Time - ADD type
Basic rear-wheel drive, no center differential, front wheels are mechanically connected

In order to make front axle connection easy and get away from electric hubs, ADD (Automatic Disconnecting Differential) was implemented, which disconnect one of front axle shafts by actuator. As a result, rotation from wheels is not transmitted to the front propeller shaft, but the front axle gears are permanently lubricated.








4WD control - electric (by "4WD" button on the transfer lever) or semi-mechanical (by lever, similar to PT-Hub). Modern models have controller instead the lever.




Shift order:
2WD→4WD - at speed below 80 km/h with accelerator released, not engage during slipping.
4WD→2WD - at any speed.
4WD-H↔4WD-L - when the vehicle is stationary and at "N" range of transmission.

ModelProductionTransmissionDifferential locking
4Runner 1851995-2002A340Frear - mechanical (opt.)
FJ Cruiser2006-..A750Frear - mechanical (opt.)
Fortuner 1502015-..AC60Frear - mechanical (opt.)
Hilux 202004-2015A340F,A343F,A750Frear - mechanical/LSD (opt.)
Hilux 1202015-..A750F,AC60Frear - mechanical (opt.)
HiLux Surf 1301989-1995-rear - LSD (opt.)
HiLux Surf 1851995-07.1998A340Frear - LSD (opt.)
HiLux N16#,17#1997-2004A343Frear - LSD (opt.)
Land Cruiser 90 (GX)1996-2002A343Frear - LSD (opt.)
Tacoma 160-1701995-2004A340Frear - mechanical (opt.)
Tacoma 200 2004-2015A340F,A750Frear - mechanical/LSD (opt.)
Tundra 401999-2006A340F,A750Frear - LSD (opt.)
Tundra 502006-..A750F,AB60F-


2.3. Multi-Mode type
Full-time four-wheel drive with the ability to disconnect front wheels, asymmetrical center differential with a forced locking or Torsen LSD

There is disconnected front-wheel drive system with ADD in this scheme, but the transfer obtain asymmetrical differential (torque distribution between front and rear wheels - 40:60). So, 4WD can be used permamently in all conditions, and front drive may be disconnected for the fuel economy only.

"+" Full-time all-wheel drive in combination with a potential economy mode.
"-" Unnecessary complex design compared to the full-time.

Modern models also have "AUTO LSD" function (at 2WD mode one of the slipping wheels is braked, emulating a partial rear differential lock) and "A-TRAC" (traction control, limiting the engine output at the start or acceleration on slippery surfaces).

H2↔H4 - speed below 80 km/h with accelerator released, not engage during slipping.
H4H→H4L - at speed below 100 km/h, not engage during slipping.
H4L↔L4L - when the vehicle is stationary and at "N" range of transmission.


H2↔H4 - at speed below 100 km/h (if temperature below -15°C - 70 km/h).
H4↔L4 - when the vehicle is stationary and at "N" range of transmission.
Center differential lock - at speed below 100 km/h


ModelProductionTransmissionDifferential locking
4Runner 1851998-2002A340Fcenter - mechanical, rear - mechanical (opt.)
4Runner 2152002-2009A340F,A750Fcenter - mechanical, rear - mechanical (opt.)
HiLux Surf 1851995-2002A340Fcenter - mechanical, rear - LSD (opt.)
HiLux Surf 2152002-2009A343F,A750Fcenter - mechanical, rear - LSD (opt.)
Sequoia 452000-2007A340F,A750Fcenter - mechanical (-2004) / Torsen + mechanical (2004-)
Sequoia 652007-..A750F,A760F,AB60Fcenter - Torsen + mechanical


2.4. Full-Time V type
Full-time four wheel drive, with a symmetrical center differential, locking by viscous coupling

The basic scheme for vans with the center differential, partially locking by viscous coupling.

"+" Full-time four-wheel drive, n not necessary to control.
"-" Low efficiency of viscous coupling, no low range in transfer.





ModelProductionTransmissionDifferential locking
HiAce KZH10#..12#1993-1995A340F+TF1BVcenter - viscous coupling, rear - LSD (opt.)
HiAce/RegiusAce 1001995-2004A45DF,A340F+TF1BVcenter - viscous coupling, rear - LSD (opt.)
HiAce/RegiusAce 2002004-..A340F,A343F+TF1BVcenter - viscous coupling, rear - LSD (opt.)
Regius/Touring HiAce 401997-2004A43DF,A45DF,A343F+ TF1BVcenter - viscous coupling, rear - LSD (opt.)
Granvia/Grand HiAce 10..201995/97-2004A343F+ TF1BVcenter - viscous coupling, rear - LSD (opt.)
Estima 201990-1999A46DF,A340F+ TF1AVcenter - viscous coupling
Estima Emina/Lucida 201992-1999A43DF,A45DF,A46DF+ TF1AVcenter - viscous coupling
LiteAce/TownAce 851999-2007A44DF+ TF1BVcenter - viscous coupling
LiteAce/TownAce Noah 501996-2007A44DF,A45DF+ TF1BVcenter - viscous coupling


2.5. Full-Time H (i-Four) type
Full-time four wheel drive, with a asymmetrical center differential, locking by hydromechanical clutch

Toyota top-model's have an advanced scheme of 4WD, similar to principle of the STD I for initially-FF cars. Full-time all-wheel drive with a center differential (torque distribution between front and rear wheels - 30:70), locking by hydromechanical clutch with electronic control. Some details here.

"+" Full-time all-wheel drive, no need to control by driver.
"-" No full locking, complicated design (system is closely linked to ABS/VSC)

ModelProductionTransmissionDifferential locking
Aristo 1401992-1997A340H + UF1AEcenter - hydromechancial clutch
Brevis 102001-2007A340H + UF1AEcenter - hydromechancial clutch
Crown 1401992-1995A340H + UF1AEcenter - hydromechancial clutch
Crown 1501995-1999A340H,A341H + UF1AEcenter - hydromechancial clutch
Crown 1701999-2004A340H,A341H + UF1AEcenter - hydromechancial clutch
Crown 1802003-2008A750H,A760H,A761H + UF1AEcenter - hydromechancial clutch
Crown 2002008-2013A760H + UF1AEcenter - hydromechancial clutch
Crown 2102013-..A760H + UF1AEcenter - hydromechancial clutch
Lexus IS 202005-2013A760H + UF1AEcenter - hydromechancial clutch
Lexus IS 302013-..A760H + UF1AEcenter - hydromechancial clutch
Lexus GS 1902005-2011A760H + UF1AEcenter - hydromechancial clutch
Lexus GS 102011-..A760H + UF1AEcenter - hydromechancial clutch
Lexus RC 102014-..A760H + UF1AEcenter - hydromechancial clutch
Mark II 901993-1996A340H + UF1AEcenter - hydromechancial clutch
Mark II 1001996-2000A340H + UF1AEcenter - hydromechancial clutch, rear - LSD (opt.)
Mark II 1102000-2004A340H + UF1AEcenter - hydromechancial clutch, rear - LSD (opt.)
Mark II Blit 1102002-2007A340H + UF1AEcenter - hydromechancial clutch
Mark X 1202004-2009A340H + UF1AEcenter - hydromechancial clutch
Mark X 1302009-..A340H + UF1AEcenter - hydromechancial clutch
Progres 101999-2007A340H + UF1AEcenter - hydromechancial clutch


2.6. Full-Time T type
Full-time four wheel drive, with a asymmetrical center differential, locking by Torsen LSD

Toyota's flagship have several simpler (compare to FT-H) 4WD scheme - with asymmetrical (40:60) Torsen differential, and gear drive to front wheels at transfer.


ModelProductionTransmissionDifferential locking
Lexus LS 402006-..AA80Fcenter - LSD Torsen


2.7. Full-Time TL (Dual Range Diff Lock) type
Full-time four wheel drive, with a asymmetrical center differential, locking by Torsen LSD with the possibility of full locking, low range

Modern mid- and full-size SUVs are obtained with full-time all-wheel drive, asymmetrical Torsen differential, full locking mechanism, chain drive to the front wheels, low range. Torque distribution between the front and rear wheels - 40:60 (nominal) and 28:72 to 58:42 (dynamic, depending on driving conditions).








Low-version have single lever (LC 120) or the controller, providing three modes - H4F, H4L, L4L. Other versions have splitted control for center differential and low range gear, thar allows to use L4F mode.
H4↔L4 - when the vehicle is stationary and at "N" range of transmission.
Center differential lock - at speed below 100 km/h

ModelProductionTransmissionDifferential locking
4Runner 2852009-..A750Fcenter - LSD Torsen + mechanical, rear - mechanical (opt.)
Fortuner 502005-2015A340F,A750F + VF4Bcenter - LSD Torsen + mechanical, rear - LSD/mechanical (opt.)
Land Cruiser Prado 1202002-2010A340F,A343F,A750F + VF4BMcenter - LSD Torsen + mechanical, rear - LSD/mechanical (opt.)
Land Cruiser Prado 1502009-..A343F,A750F + VF4BMcenter - LSD Torsen + mechanical, rear - mechanical (opt.)
Land Cruiser 2002007-..A750F,AB60F + JF2Acenter - LSD Torsen + mechanical, rear - LSD/mechanical (opt.)
Lexus GX 1502009-..A750F,A760F + VF4BMcenter - LSD Torsen + mechanical
Lexus LX 2002007-..AB60F + JF2Acenter - LSD Torsen + mechanical


Abbreviations: TM - transmission (gearbox, CVT), TR - transfer, FD - front differential, RD - rear differential, CD - center differential, CDC - hydraulic clutch, VC - viscous coupling, EC - electromechanic coupling.


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