Balancer shafts

Fig 1: View Of Balancer Shafts

Courtesy of SAAB-SCANIA OF AMERICA, INC.

The balance shafts are intended to absorb vibration and second order forces from the moving parts of the engine and at the same time reduce the level of unwanted engine noise. They are driven via a separate chain circuit in the timing cover. See BALANCER SHAFTS  .