Audi A4

since 1994 release

Repair and operation of the car

The connected all-wheel drive

Until then the full drive was almost inseparably connected with concept of the cross-country vehicle. The concept of the full drive used in this family of cars was simple:

• In addition to the standard drive (the engine ahead, the drive behind) to a forward axis the second transmission by branch of transfer and the additional driveshaft was simply laid. The movement in the usual mode happened to the standard drive, and only if it was demanded by road conditions, forward transmission of the drive was connected. This design with the connected all-wheel drive is used and today in cross-country vehicles.
• Shortcoming: For the movement on solid soil the all-wheel drive has to be switched-off as on turns forward wheels pass a bigger piece of a way, than back. Different frequency of rotation of wheels leads to an overstrain of transmissions.
• Effect: the car copes hardly, on turns for removal of tension from the drive the wheel rubs with very small probuksovyvaniye through certain intervals – the car jumps up.

Constant all-wheel drive

When the idea of the constant all-wheel drive came to mind, it was necessary to think up a way of alignment which would not allow an overstrain of both drives of axes relatively each other. This problem is solved by so-called central differential.

Differentials are known in automotive industry long ago. They divide forces between the right and left driving wheel. In this case alignment because, as we know, on turns the wheel, external in relation to turn, always passes a bigger piece of a way, than an internal wheel too is necessary. This alignment is provided with axis differential. It provides the axis drive at simultaneous possibility of free rotation of both driving wheels relatively each other.

The one who coordinated on the way in the winter, knows insidiousness of a subject: the wheel standing on ice is turned, the opposite wheel on rough soil does not transfer effort and costs.

One becomes clear: such differential is no good as central as just the opposite case is necessary. Force has to be directed there where wheels will be able to transfer you to soil, namely: where there is a paving with stickiness. And as it never happens known, distribution of force has to be carried out automatically and and immediately. After various development stages of the blocking central differential with manual connection today the so-called distributive torsen-differential is built in the Audi Quattro models.