The difference between single-action and double-action shocks primarily relates to how they control suspension movement:

Single-Action Shocks
These shocks control movement only in one direction, usually the rebound (extension) of the suspension. The shock provides resistance mainly when the suspension extends after a bump. They use lever arm or lever-type designs common in older trucks like the 1946 Chevy. Compression (when the wheel moves up) is controlled by the springs rather than the shock. Most stock shocks on 1946 Chevy 3/4-ton trucks were single-action lever arm shocks. They tend to provide a softer ride but less control over suspension during compression.

Double-Action Shocks
These shocks provide damping during both compression (bumping) and rebound (extension) of the suspension. They offer more control and improved stability because they resist suspension movement in both directions.
Modern double-action shocks usually have internal valving to provide this dual resistance.

Double-Action Shocks were not original equipment on 1946 Chevy trucks but can be installed as upgrades for better handling and ride quality. Don't know if a double action level type shock exists. Switching to a double action tube type shock would most likely require modification to mount.

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