Does the pain occur on just one side of the body or on both sides?
The bucket seat may be too low and there is no back support. Place a pillow or cushion behind the back to fill in the gap between the driver’s back and the back of the bucket seat. The lack of back support while driving in a low driver’s side bucket seat would bring on lower back pain across the lower back and this pain is felt on both sides.
If the side pain occurs on only one side, then it may be that the bucket is too farther back from the steering wheel and the leg is always stretched straight to reach the gas pedal. This stiffness in the leg while driving may bring on pain on either side of the lower back. Place the steering wheel in the uppermost position, and move the bucket seat forward to shorten the distance between the body and the gas pedal. This can also be done by sitting on a cushion while driving. Sitting on a cushion elevates the butt and the knee can bend more easily. This lessens leg muscle tension while stepping on the gas pedal.