Abstract: In a onboard weighing system for a vehicle the load is carried by a load frame which during the transport mode rests on the vehicle support frame and for weighing, after the vehicle has come to a stop, a force is applied to raise the load frame off the vehicle support frame and onto a load cell so that the load cell will produce a signal indication of the weight of the load. As a feature the load cell is pivotally mounted in gimbal rings to compensate for any pitch or roll angles due to tilting of the vehicle and/or the load frame. As yet another feature a mechanism is provided to securely but releasably lock the load or weigh frame onto the vehicle support frame during the transport mode.