1942 - 1947 Chevrolet Shop Manual



	*2-10*

	also be removed for making piston valve changes. However, on this type of opposed cylinder shock absorber the rebound and compression relief valves are located in the ends of drilled passages cast on the outside of the body. These valves are held in place by valve nuts and gaskets which are removable for changing valves. Operation As the arm moves upward on the compression stroke the compression piston moves toward right, Fig. 13. displacing the fluid in the compression end of the shock absorber. On very slight or slow axle movements the fluid flows only through the bleeder hole of the compression valve, as indicated by the dotted arrow, and into the rebound end of the cylinder. Under the influence of rapid movement, the additional pressure lifts the valve from its seat against the tension of the valve spring and then flows into the rebound end of the cylinder. At the same time the rebound piston intake valve opens, allowing fluid to flow into the rebound end of cylinder as indicated by the white arrow, Fig. 13. During the rebound stroke, or as the arm moves downward, the direction of fluid flow is reversed. The piston moves away from the arm end of the shock absorber, forcing fluid from the rebound end of the cylinder. During slow action fluid flows only through the bleeder hole of the rebound valve into the compression end of the cylinder. During rapid action the rebound valve is lifted from its seat and the fluid passes at a pressure controlled by the relief valve spring into the compression end. At the same time, the intake valve of the compression piston opens, allowing fluid to pass into the compression end of the cylinder. Another type of front double-acting shock absorber available as special equipment on all commercial and truck models is shown in Fig. 14. This is an opposed cylinder design with outside rebound	relief valve. The compression relief valve is carried in the compression piston. The action of this unit is a combination of the internal valve type and external valve type. The compression piston is fitted with a spring-loaded compression relief valve. This valve has a bleeder hole in the valve stem. Under normal compression,

		Fig. 15—Action During Spring Compression when the fluid pressure is applied by the piston, transfer of fluid takes place through the bleeder hole, but for violent road shocks the valve opens and allows a more rapid transfer of fluid past the valve seat as well as through the bleeder hole. At the same time fluid enters the rebound cylinder through the rebound piston intake valve as shown in Fig. 15.


		Fig. 16—Action During Spring Rebound During the rebound stroke, fluid is forced through the rebound relief valve at a pressure controlled by the relief valve spring tension. At the same time the intake valve in the compression piston opens, allowing fluid to flow into the compression end of the cylinder. This action is shown in Fig. 16.
	Fig. 14—Cross-Section of Combination Internal-External Relief Valve Double-Acting Shock Absorber