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Lancia Delta HF

Full-time all wheel drive.

Transmission type

Full-time all wheel drive with an epicyclic center differential paired with a Ferguson viscous coupling; Torsen-type rear differential with 5 to 1 wheel torque ratio.

Three differentials are at the heart of the system. Drive to the front wheels is linked through a free-floating differential; drive to the rear wheels is transmitted via a 56/44 front/rear torque-splitting Ferguson viscous-coupling-controlled epicyclic central differential. The real innovation as far as production cars are concerned however, lies between the rear wheels.

The Torsen (torque sensing) rear differential is similar to that found on McLaren Formula 1 cars. The result of combining these differentials in this configuration is an automatic-thinking four-wheel-drive system which requires no manual input from the driver, yet ensures maximum potential traction at any given time.

The Torsen differential is a true 'intelligent' differential in the way it distributes torque. It divides the torque between the two wheels according to the grip available and it does it without ever locking fully; maximum lockup is 70 per cent.

Standard differentials are either free-floating or self-locking. Free-floating systems are good at differentiating between wheel speeds on bends, but always supply the same amount of torque to both wheels. In this situation, however, there is a risk that the wheel with the lighter load (on an incline, for example) or less grip, will lose traction. To counteract this possibility, totally self-locking differentials ensure that both wheels rotate at the same speed but in doing this, prevent free differentiation in cornering, to the detriment of handling and stability.

Fiat Tempra 4x4 Lancia Delta HF 4x4 8 valve HF Integrale 16 valve HF Integrale Alfa 155 Q4, Lancia Delta Evoluzione 1,2
Final drive ratio 3.560:1 2.944:1 3.111:1 3.111:1 3.350:1
Torque split front 56% 56% 56% 47% 47%
rear 44% 44% 44% 53% 53%

Figure: Lancia Delta HF 4wd

Figure: Lancia Delta HF Integrale rear Torsen locking differential (lower left), viscous coupling(2) locking planetary gear center differential(1) (lower right). On the top - manually locking rear differential for Lancia Dedra Integrale.

Figure: lancia delta hf integrale

Figure: lancia delta hf integrale rally

Figure: lancia delta hf integrale rear drive shaft

You have better pictures or videos of Lancia Delta Hf that you can contribute? Please send them to !

Lancia Delta / Lancia Dedra / Fiat Tempra / Alfa Romeo 155

Figure: Lancia Delta / Lancia Dedra / Fiat Tempra / Alfa Romeo 155 4wd power distribution unit. Planetary center differentical is located on the left, near the left driveshaft. Viscous coupling is located on the right side near the right driveshaft.

Figure: Lancia Delta / Lancia Dedra / Fiat Tempra / Alfa Romeo 155 4wd power distribution unit. 100% of the power goes to the planetary center differential (red), from there, the power is distributed between the front axle (yellow) and the rear axle (blue). When slipping occurs, the viscous coupling locks the front and rear shafts together. The engine is rotating the outer gear of the planetary gear center differential. Power to the front wheels is taken from the sun gear (center gear). Power to the rear wheels is taken from the planet gears (the smallest gears in the middle).

Figure: Lancia Delta / Lancia Dedra / Fiat Tempra / Alfa Romeo 155 4x4 center differential unit.

Do you think this information about Lancia Delta / Dedra / Fiat Tempra / Alfa Romeo 155 is incorrect? Please send us what you know to or leave a comment below.

Lancia Delta S4

Full-time all wheel drive with an epicyclic center differential paired with a Ferguson viscous coupling.

Figure: Lancia Delta S4 four wheel drive

Have you seen a better description of Lancia Delta S4 on the web? Please send us the link to or post it in a comment below!

Lancia y10 4wd

Part-time all wheel drive. Button-operated. Vacuum-operated rear axle disconnect system. When in 2wd mode, the driveshafts are disconnected from the transfer box and from both rear wheels.

Figure: lancia y10

Figure: lancia y10

Figure: lancia y10

Do you own Lancia Y10 4Wd? Can you please make a photo of the car's 4x4 transmission, switches, dashboard lights, etc. and send it to ?

This is a Wiki, so feel free to correct any factual or grammatical error. Test here before posting.

There are 3 comments
July 07, 2016 - 23:25


Can u say me please, in which book u found this picture? (The description of the Picture is in german)

Is there a technical book of the Group b cars with those fantastic descriptions?

Reply to Dan
July 28, 2016 - 22:11

Hi, it came from the Internet

October 14, 2015 - 00:55

Why don't Lancia delta s4 make a new 2017 ( twin turbos & supercharged v4 DOHC I-VTEC IMA engine ) with 12,000 rpm red line & 700 hp . A new body style like the Harald Belker Lexus 2054 Los Angeles police car with active rear wings for cornering , stopping & speed.

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