A system for varying the weight over one or more axles of a truck carrying a container, the container, the truck and the one or more axles being arranged in the manner of a vacuum tank mounted on a vacuum truck having a front axle and one or more rear axles, the system including: a telescopic subframe comprising one or more elongate structures, each elongate structure having a fixed part and a telescoping part telescopically engaged with the fixed part, and each fixed part fixedly attached to a mounting frame of the truck so that the telescopic subframe lays substantially horizontally on the mounting frame; and one or more hydraulic cylinders operable by a controller, each hydraulic cylinder attached to and operably coupling the truck and the vacuum tank.