Hendrickson S-25593 Surelok Air Spring Actuator Assembly
Updated June 9, 2026
The Hendrickson S-25593 Surelok Air Spring Actuator Assembly is a small auxiliary air spring used on Hendrickson SureLok trailer suspension systems. Its primary function is to actuate a height-lock arm that locks the trailer's ride height during dock loading, protecting the dock plate and trailer body from damage.
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How It Works
This actuator bag is part of the SureLok height control system. When air pressure is applied, the bag expands to move a locking arm that secures the suspension at a preset ride height. This prevents the trailer from sinking or rising during loading/unloading, reducing stress on the dock equipment and trailer structure. The assembly includes an air fitting and mounting hardware, and uses a 1/8" NPT air port.
Common Failure Symptoms
A failed actuator bag may cause the trailer to drift up or down while parked at a dock, leading to unsafe loading conditions. Visible cracks or leaks in the rubber bellows, inability to hold air pressure, or a broken mounting bracket are common signs of wear. The height-lock arm may not engage or disengage properly, resulting in suspension movement during loading.
Installation Notes
This assembly is designed as a direct OEM replacement for Hendrickson SureLok systems. Installation typically involves removing the old actuator bag, attaching the new unit with the supplied speed nuts, and connecting the air line to the 1/8" NPT port. Ensure the mounting bracket is secure and the bellows are not twisted. Cross-reference numbers include ABSZ70-5593, C25593, HT-S-25593, S24488, L856036, and HT263.
