The machine-tractor unit is a key element in an implementation of technological operations in the cropping. Running gears with wheeled and caterpillar propulsion device are used in the modern tractors. During an interaction of the ground with tractor propulsion devices, the ground is pulverized on one side and it is compacted on the other side during the slipping. Besides, the wheeled movers have the slipping several times higher than caterpillar movers. The aim of the research is an analysis of running gears of machine-tractor units and their influence on the quality of performed technological operations. The paper discusses an analysis of parameters of wheeled and replaceable caterpillar movers to the tractor K-701, which have the same dimensions. One of the main external influences on the unit is the surface profile of the field. The main source of tractor oscillations are the unevennesses of the way. At the same time, characteristic areas for the operation of machine-tractor units are very various, the most characteristic of them are a stubble field, a plowed field, a prepared field, a field road and others. The analysis of spectral densities of the surface profile of the field on which the tractor operates shows that with increasing speed, the spectral density decreases rapidly, and the maximum of the spectral density shifts toward higher values of the frequencies. It has been established that the frequency range, which has the greatest effect on the machine-tractor unit on the basis of the tractor K-701 on the replacement caterpillar mover 1...4 sec-1, on the wheel mover - 1...7 sec-1. The replaceable caterpillar mover for a 5 сlass tractor has significant advantages over a wheeled mover, since it filters (smoothes) 2,1...2,8 times more irregularities, which improves working conditions, smooth of running and other indicators of the machine-tractor unit.