, there are three types of Torsen differentials. • The original
Torsen T-1 (Type A) uses crossed axis
helical gears to limit torque split. The Type I can be designed for higher torque bias ratios than the Type II, but typically has higher backlash and the potential for noise, vibration, and harshness (NVH) issues, and requires a precise setup/installation. • The later
Torsen T-2 (Type B) uses a
parallel gear arrangement to achieve a similar effect. There is also a specialist application of the T-2, known as the
T-2R (RaceMaster). • The latest
Torsen T-3 (Type C) is a
planetary type differential, in that the nominal torque split is not 50:50. The Type C is available as single or twin version; the Torsen twin C differential has front and center differential in the same unit. The Torsen T-3 is currently employed as the center differential in all non-
Haldex Traction Audi models with a ZF-sourced automatic transmission
Quattro four-wheel drive, such as:
Audi A6,
Audi A7, and
Audi Q7. Audi uses a mechanical "Crown Wheel" center differential for all longitudinal implementations using dual-clutch transmissions, such as the 2013/14 S4/RS4.
Alfa Romeo used a Torsen C twin differential in the
Alfa Romeo 156 Crosswagon Q4 and also in the
159,
Alfa Romeo Brera and Spider Q4 models. Also,
Toyota uses a Torsen T-3 in the center differential of the
4Runner Limited,
FJ Cruiser 6-speed manual,
Sequoia,
Land Cruiser, Land Cruiser Prado and
Lexus GX470, with manual locking feature, and
General Motors used a Torsen T-3 center differential in the transfer case of the
Chevrolet TrailBlazer SS and
Saab 9-7X (Aero model only).
Behaviour of Torsen differentials The Torsen differential works just like a conventional
differential, but can lock up if a torque imbalance occurs, the maximum ratio of torque imbalance being defined by the torque bias ratio (TBR). When a Torsen has a 3:1 TBR, that means that one side of the differential can handle up to while the other side would have to only handle of applied torque. During acceleration under asymmetric
traction conditions, so long as the higher traction side can handle the higher applied torque, no relative
wheelspin will occur. When the traction difference exceeds the TBR, the slower output side of the differential receives the tractive torque of the faster wheel multiplied by the TBR; any extra torque remaining from applied torque contributes to the
angular acceleration of the faster output side of the differential. The TBR should not be confused with the uneven torque-split feature in the planetary-type Torsen III. The planetary gearset allows a Torsen III center differential to distribute torque unevenly between front and rear axles during normal (full traction) operation without inducing wind-up in the drivetrain. This feature is independent of the torque bias ratio.
Torsens in front and/or rear axles When a vehicle is in a turn, the outer wheel will rotate faster than the inner wheel. Friction in the differential will oppose motion, and that will work to
slow the faster side and
speed up the slower/inner side. This leads to asymmetric torque distributions in drive wheels, matching the TBR. Cornering in this manner will reduce the torque applied to the outer tire, leading to possibly greater cornering power, unless the inner wheel is overpowered (which is easier to do than with an open differential). When the inner tire (which has less traction due to weight transfer from lateral acceleration) is overpowered, it angularly accelerates up to the outer wheel speed (small percent wheel spin) and the differential locks, and if the traction difference does not exceed the TBR, the outer wheel will then have a higher torque applied to it. If the traction difference exceeds the TBR, the outer tire gets the tractive torque of the inner wheel multiplied by the TBR, and the remaining applied torque to the differential contributes to wheel spin up. When a Torsen differential is employed, the slower-moving wheel always receives more torque than the faster-moving wheel. The Torsen T-2R RaceMaster is the only Torsen to have a preload
clutch. So, even if a wheel is airborne, torque is applied to the other side. If one wheel were raised in the air, the regular Torsen units would act like an open differential, and no torque would be transferred to the other wheel. This is where the parking brake "trick" can help out. If the parking brake is applied, assuming that the parking brake applies even resistance to each side, then the drag to the airborne side is "multiplied" through the differential, and TBR times the drag torque is applied to the other side. So, the ground side would see (TBR X drag torque) minus drag torque, and that may restore motion either forward or in reverse. In Hummer/
HMMWV applications, there are both front and rear Torsen differentials, so the use of the main brakes will operate this "trick" on both axles simultaneously.
Torsen users Torsen differentials are used in many of the various
Audi quattro models, excluding the
A3 and S3 and
TT, which have
transverse-mounted engines and use Haldex Traction 4WD systems. It is also used in the third- and fourth-generation
Toyota Supra (Optional) and third-generation
Toyota Soarer, the B5 platform revision of the
Volkswagen Passat 4motion (based upon the
Audi A4),
Mazda MX-5/Miata 1994 to 1995 have a Torsen Type I and late 1995 to 2002 models have a Torsen Type II, the 2002-2003 model year of the
Nissan Maxima SE 6 speed manual, the
Honda S2000, and 1999-2002 S15 Nissan Silvia Spec R. The
Lancia Delta Integrale, the
Peugeot 405 T16, as well as the 1999-2002 model
Pontiac Firebird and
Chevrolet Camaro, had a Torsen differential. Rover Group fitted Torsen type 1, and later type 2, units to their range of high performance, front-wheel drive turbocharged models (220, 420, 620ti, and 800 Vitesse). The use of the Torsen differential was preferred by Rover Group; it is much better at controlling wheel spin in front-wheel drive vehicles than electronic systems which reduce engine power and therefore performance. The
Humvee uses two Torsens, front and rear, with a normal manually lockable center differential (NVG242HD AMG transfer case) in the center. Other users of the Torsen limited-slip differential include the
Toyota GT86 and the Subaru BRZ, both released in 2012. The first Ford company vehicle to use a Torsen differential was the 2002 Ford Ranger FX4 (renamed in FX4 Level II from 2003) all of which used T-2R in the rear differential only. Starting in 2012, the Ford F-150 SVT Raptor uses a front Torsen differential and the Ford Mustang Boss 302 uses a rear Torsen differential.
AMG offered Torsen differentials as an option as early as 1988 for new as well as for retrofitting for 107, 116, 123, 126 series Mercedes Benz cars. Toyota Altezza (sold in Europe, the U.S. and Canada as Lexus IS200 and IS300) came with a Torsen differential. For Lexus models it was included with all IS300 models with manual transmission and with the IS200 Sport, and was optionally factory equipped with automatic transmission. The Toyota Altezza was standard on all manual transmission SXE10 models (with the 5th-generation Beams 3S-GE engine and J160 6-speed manual transmission). ==Torsen applications==