All-Trac
Encyclopedia
All-Trac was a proprietary full time symmetric all wheel drive system used on a variety of Toyota badged models from 1988 to 2000. It was considered a revolutionary advance for all-wheel drive automobiles into the mainstream consumer market and its electronic/vacuum controlled locking center differential was rare in a passenger car. The system originated in Japan under the GT-Four moniker in 1986, but was not released in the U.S. until 1988 under the All-Trac moniker.
, front differential, center differential and transfer case are all one large assembly and are connected to the transversely mounted engine. The transmission bell housing, front differential and center differential can be separated from the transfer case sub assembly. The transmission output shaft feeds power into the front/center differential assembly (the center differential is contained within the front differential). The front differential distributes the power to the front wheels, while the center differential distributes power to the transfer case that will send power to the rear differential. In most of the models, when the transfer case is not locked the majority of the power is routed to the front wheels as would be in a traditional Toyota FWD
automobile.
For all manual transmission models except Previa, and the 1988 and newer Celica, there is a small button inside the vehicle labelled Center Diff. Lock and when activated, the transfer case locks, resulting in the power distribution to be 50/50 between the front and rear of the vehicle. The wheels themselves are not always going the same speed because there are still the open front and open rear differentials allowing for differences in wheels speed from left to right. The final result of this is that if the vehicle is in a situation where traction is uneven or poor (i.e. muddy or snowy), all four wheels will have power transmitted to them, allowing the vehicle to use the wheels that still have traction to move the car. However, due to the open rear and front differentials, if the road conditions are very slick the wheels with the least amount of traction will still spin at a faster rate then those that do have traction.
For the Celica, the original ST165 GT-Four of October 1986 had "Center Diff. Lock" with switch located near the hand brake, and starting from the facelift model of October 1987 came with transfer case contains a viscous coupling unit that provides 50/50 power distribution to the front and rear differentials at all times, as in the Previa All-Trac models. Neither the Previa nor the Celica have a lockable transfer case, but the viscous coupling can be temporarily disabled for testing purposes via a selector switch on the transfer case assembly. The vehicle should not be driven with the viscous coupling disabled as transfer case or transmission damage will occur. Very few Celicas also had a Torsen
rear differential. This style of differential is like an open differential under normal conditions, but when one of the rear wheels starts to lose traction, it will transmit power to the wheel with the most available traction.
The ST205 chassis GT-Four
in Japan continued to use the same system that was in U.S. Celica All-Trac, and all of the rear differential were upgraded to a Torsen
differential.
Technical information
The All-Trac system had five main parts: the front differential, rear differential, center differential, the transmission, and the transfer case. The transmissionTransmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...
, front differential, center differential and transfer case are all one large assembly and are connected to the transversely mounted engine. The transmission bell housing, front differential and center differential can be separated from the transfer case sub assembly. The transmission output shaft feeds power into the front/center differential assembly (the center differential is contained within the front differential). The front differential distributes the power to the front wheels, while the center differential distributes power to the transfer case that will send power to the rear differential. In most of the models, when the transfer case is not locked the majority of the power is routed to the front wheels as would be in a traditional Toyota FWD
FWD
FWD may refer to:* Front-wheel drive, a common method of vehicle propulsion.* FWD Campaign from USAID* Free World Dialup , a non-commercial Voice over IP network....
automobile.
For all manual transmission models except Previa, and the 1988 and newer Celica, there is a small button inside the vehicle labelled Center Diff. Lock and when activated, the transfer case locks, resulting in the power distribution to be 50/50 between the front and rear of the vehicle. The wheels themselves are not always going the same speed because there are still the open front and open rear differentials allowing for differences in wheels speed from left to right. The final result of this is that if the vehicle is in a situation where traction is uneven or poor (i.e. muddy or snowy), all four wheels will have power transmitted to them, allowing the vehicle to use the wheels that still have traction to move the car. However, due to the open rear and front differentials, if the road conditions are very slick the wheels with the least amount of traction will still spin at a faster rate then those that do have traction.
For the Celica, the original ST165 GT-Four of October 1986 had "Center Diff. Lock" with switch located near the hand brake, and starting from the facelift model of October 1987 came with transfer case contains a viscous coupling unit that provides 50/50 power distribution to the front and rear differentials at all times, as in the Previa All-Trac models. Neither the Previa nor the Celica have a lockable transfer case, but the viscous coupling can be temporarily disabled for testing purposes via a selector switch on the transfer case assembly. The vehicle should not be driven with the viscous coupling disabled as transfer case or transmission damage will occur. Very few Celicas also had a Torsen
Torsen
Torsen is a type of differential used in automobiles. It was invented by American Vernon Gleasman and manufactured by the Gleason Corporation. Torsen is a contraction of Torque-Sensing...
rear differential. This style of differential is like an open differential under normal conditions, but when one of the rear wheels starts to lose traction, it will transmit power to the wheel with the most available traction.
Model series
- 1988–1991 Camry, DX and LE trim, 4 cyl 1998 cc 3S-FE
- 1988–1992 CorollaToyota CorollaThe Toyota Corolla is a line of subcompact and compact cars manufactured by the Japanese automaker Toyota, which has become very popular throughout the world since the nameplate was first introduced in 1966. In 1997, the Corolla became the best selling nameplate in the world, with over 35 million...
, std trim, SR5, 4 cyl 1587 cc 4A-FE - 1990–2000 Previa, DX, LE, LE supercharged trim, 4 cyl 2438 cc 2TZToyota TZ engineThe Toyota TZ engine is a series of water-cooled inline four-cylinder gasoline engines from Toyota Motor Corporation. They feature dual overhead camshafts and 4 valves per cylinder...
- 1988–1993 Celica All-Trac TurboToyota Celica GT-FourThe Toyota Celica GT-Four is a high performance model of the Celica liftback, with a turbocharged 3S-GTE engine, and full-time AWD. It was created to compete in the World Rally Championship, whose regulations dictate that a manufacturer must build road-going versions of the vehicle in sufficient...
1988–1989 for ST165 chassis and 1990-1993 for ST185 chassis with 4cyl turbo 1998 cc 3S-GTE
Predecessors and successors
Toyota's GT-Four / All-Trac system was originally released on the ST165 chassis Celica that was only available in Japan. The system used a locking transfer case that was the same as the electric/vacuum system that is found on U.S. All-Trac Camrys. For the 1988 model year when the U.S. All-trac system arrival, the Celica GT-Four / All-Trac had changed the transfer case to a viscous coupling unit.The ST205 chassis GT-Four
Toyota Celica GT-Four
The Toyota Celica GT-Four is a high performance model of the Celica liftback, with a turbocharged 3S-GTE engine, and full-time AWD. It was created to compete in the World Rally Championship, whose regulations dictate that a manufacturer must build road-going versions of the vehicle in sufficient...
in Japan continued to use the same system that was in U.S. Celica All-Trac, and all of the rear differential were upgraded to a Torsen
Torsen
Torsen is a type of differential used in automobiles. It was invented by American Vernon Gleasman and manufactured by the Gleason Corporation. Torsen is a contraction of Torque-Sensing...
differential.
See also
- quattro - AudiAudiAudi AG is a German automobile manufacturer, from supermini to crossover SUVs in various body styles and price ranges that are marketed under the Audi brand , positioned as the premium brand within the Volkswagen Group....
branded four wheel drive system - 4motion4motion4motion is a registered trademark of Volkswagen AG, used exclusively on Volkswagen-branded automobiles which utilise four-wheel drive systems. Volkswagen has previously used the term "Syncro" for its 4WD models....
- VolkswagenVolkswagenVolkswagen is a German automobile manufacturer and is the original and biggest-selling marque of the Volkswagen Group, which now also owns the Audi, Bentley, Bugatti, Lamborghini, SEAT, and Škoda marques and the truck manufacturer Scania.Volkswagen means "people's car" in German, where it is...
branded four wheel drive system - 4Matic4MATIC4Matic is the name of an AWD four-wheel drive system developed and used by Mercedes-Benz. It is designed to increase traction in slippery conditions....
- a four wheel drive system from Mercedes-BenzMercedes-BenzMercedes-Benz is a German manufacturer of automobiles, buses, coaches, and trucks. Mercedes-Benz is a division of its parent company, Daimler AG... - ATTESAATTESAATTESA is a four-wheel drive system used in some automobiles produced by the Japanese automaker Nissan, including some models under its luxury marque Infiniti.-ATTESA:...
- a four wheel drive system from Nissan - xDriveBMW xDriveBMW xDrive is BMW's four-wheel drive system that powers the X1, X3, X5, X6 and 2006 and later xd and xi 3 Series, 5 Series and 7 Series models. BMW confirmed it has ....
- a four wheel drive system from BMWBMWBayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands... - SH-AWDSH-AWDSuper Handling-All Wheel Drive or SH-AWD is a full-time, fully automatic all-wheel drive traction and handling system designed and engineered by Honda Motor Company. The system was announced in April 2004, and first introduced in the North American market in the second generation 2005 model year...
- a four wheel torque vectoring system from HondaHondais a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than... - S-AWC - a torque vectoring four-wheel drive system from Mitsubishi MotorsMitsubishi Motorsis a multinational automaker headquartered in Minato, Tokyo. In 2009 it was the fifth-largest Japan-based automaker and the 17th-largest in the world measured by production...
Reference
- 1990 Toyota Celica New Car Features Book by Toyota Motor Sales USA, printed in 1989.
- 1990 Toyota Celica Brochure.
- 1993 Toyota Celica Brochure.