9. Transmission

Transmission units

1, 3 – drives of forward wheels;
2 – forward bridge;
4 – coupling;
5 – transmission;
6 – forward driveshaft;
7 – intermediate shaft;
8 – transfer case;
9 – lever of gear shifting of the transfer case;
10 – lever of blocking of differential;

11 – back driveshaft;
12 – back bridge;
I – the differential is unblocked;
II – the differential is blocked;
By III – the lowest transfer is included;
IV – neutral situation;
V – the highest transfer is included

The Field car – all-wheel drive, i.e. leaders are all wheels. The four-wheel drive – constant: the torque from the engine is always transferred to both axes at once (bridges are not disconnected). Such scheme increases passability of the car, at the same time reducing loads of transmission knots, but increases fuel consumption a little.

Forward and back bridges are connected through the interaxal differential allowing lobbies and back wheels to rotate with different angular speeds depending on a trajectory and traffic conditions. The interaxal differential is located in the transfer case and is similar to the interwheel differentials located in forward and back bridges. However, unlike them, the interaxal differential can be blocked forcibly (the lever of blocking is on a floor tunnel). At the same time forward and back driveshafts become rigidly connected among themselves and rotate with an identical frequency. It considerably increases passability of the car (on slippery rises, in dirt, snow, etc.), but worsens controllability and increases wear of details of transmission and tires on a covering with good coupling. Therefore blocking of differential can be used only for overcoming difficult sites and at a small speed. For the warning of the driver of the included mode of blocking the control lamp on the dashboard serves.

It is possible to include blocking of differential at the movement of the car if wheels do not slip. Blocking of interaxal differential does not save the car from danger of "diagonal posting" when one of wheels on each axis loses coupling with soil – in this case pour soil under the hung-out wheels or undermine it under the others.

For increase in the torque brought to wheels the lowest transfer serves in the transfer case, its transfer number – 2,135. The highest transfer intended for normal traffic conditions has transfer number 1,20. Thus, the driver can use one of two rows of transfer numbers – with the highest or lowest transfer in the transfer case. Total transfer numbers of the "top" row (with I on the V transfer) – 4,40; 2,52; 1,63; 1,20; 0,98, "lower" – 7,82; 4,47; 2,90; 2,13; 1,75. The lowest transfer in the transfer case is included before overcoming snow-covered, sandy sites, steep slopes, at towage of freights, etc. when the lack of draft of the engine or for the movement with very small speed is felt. It is necessary to include the lowest transfer in the transfer case in advance, on the standing car as the coupling of gear shifting has no synchronizers. The highest transfer at some skill manages to be included also at the movement with a speed not higher than 30-35 km/h, however, if there is an opportunity, it is better to reduce speed or to stop.

The car with the constant four-wheel drive imposes special requirements to tires. They have to be identical not only by the size, but also on wear degree. Different radiuses of swing of tires will cause the increased wear of differentials under usual traffic conditions, and at the included blocking — the increased wear of other details of transmission and pro-slipping of wheels.