Abstract: An alarm system that indicates to an operator the status of locking pins of a vehicle sliding axle assembly. The alarm system includes an alarm valve coupled to the locking pins and in fluid communication with an alarm. When the pins are unlocked from a vehicle component, the alarm valve is configured in an alarm mode to indicate the unsecured condition of the assembly. In this mode, air is diverted from the vehicle brakes to sound the alarm, thereby informing an operator that the pins are improperly engaged. In one embodiment, the alarm valve is in communication with or includes a pressure relief valve, which diverts a sufficient amount of air from the vehicle brakes so that the brakes cannot be released. When the pins are properly locked to secure the slider axle assembly, the alarm valve does not divert air from the brakes to sound the alarm.