Timber transport in the forest is a very complex operation, and expensive from an energy point of view. Furthermore, in some cases, this operation can be very difficult and dangerous in unfavorable conditions of the road surface, which mainly occur in winter (frozen ground) and in spring (muddy ground). The goal of this study was to develop an innovative transmission hydraulic control system for trailer motor axle that would allow correlating the forward speed of the trailer with that of the tractor, which is not necessarily always the same. In detail, the innovative motor axle of the trailer is driven by a hydraulic motor through a pump controlled electronically. A specific software is able to correlate the forward speed of the trailer with the speed of the tractor in any operating situation, thanks to the information given by a potentiometer screwed behind to the trailer component coupled to the tractor. The innovative system developed to control the trailer motor axle provides the possibility to use the trailer with any type of tractor, not requiring long and complex adjustment of tractor and trailer, since it is completely independent from the type of the tractor used.