Trucks of the early years were often exposed to the rough terrain of local gravel roads as well as the dirt ruts on the farm. Quality, long life shock absorbers were a necessity. Therefore, trucks from the mid 1930′s through 1949 continued with a proven design carried over from earlier vehicles.
The highly successful lever action shocks had been used since the 1930′s on GM cars and trucks. They should not be confused with knee action shocks on the front of mid 1930′s Chevrolet passenger cars. This is a totally different system.
Lever action shocks are simple in design but excellent in quality and long life. Their cast iron fist sized housing, bolted to the frame rail, contains hydraulic fluid and basic internal parts. The fluid is forced through a small internal orifice as the vehicle encounters uneven road surfaces. The slowness of the moving liquid inside the shock gives a cushion action that softens the ride.
The workmanship built into these lever action shocks are an excellent example of quality GM engineering. On many trucks throughout the country these factory shocks are continuing to serve after 50 years and with the abuse of no past servicing.
The weak point is the small rubber bushings at each end of the link, not the actual shock assembly. During many restorations the hydraulic fluid is changed, link bushings replaced, and the shock continues to operate like new.
Single action shock absorbers were standard equipment of the 1/2 ton and 3/4 ton trucks with an optional double action type available for more heavy duty requirements. A single action design has resistance only on the upward direction of the wheel while a double action style slows wheel movement on rough roads in both directions.
Basically the horizontal arm extending from the shock housing is attached to a vertical link that extends upward from the axle. The movement of the tire then causes this link and shock arm to also move, thus forcing of hydraulic fluid between chambers inside the shock housing giving a cushioning to road bumps.
In 1950, the lever action units were discontinued and replaced on new trucks with a modern tube type sheet metal shock. (This design continues to be used on today’s vehicles.) It should be strongly emphasized, the lever action shock absorber was not discontinued because it was inferior, but rather because the new style cost much less to produce and install. It was simply a matter of economics. The fact that lever action shocks had the potential to last 50 years over the 3 to 4 years of the modern unit did not prevent the change over!