Tag-Axle Suspension Dump Switch
The optional tag-axle suspension is a non-liftable, full-time suspension designed to increase the Gross Vehicle Weight Rating (GVWR). It is used when the rear suspension/axle will be loaded to a weight greater than 20,000 lb (9072 kg). Under certain conditions, air can be exhausted from the air springs to improve maneuverability or traction on the drive axle via the tag-axle suspension dump switch.
The tag-axle suspension dump switch is operated by a three-position, dash-mounted rocker switch. See Fig.. The three positions of the switch operate as follows:
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TAG DUMP AUTO (top position)—The tag axle air bags dump when the vehicle is in reverse.
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DISABLE (middle position)—The tag axle air bags will not dump.
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MANUAL (bottom position)—Pressing the MANUAL switch dumps the tag axle air bags if the transmission is in drive and vehicle speed is 8 mph (13 km/h) or less. Pressing the MANUAL switch a second time changes the air bag mode from dump to fill.
Fig. 1, Tag-Axle Suspension Dump Switch
Warning: If the vehicle is equipped with an air suspension system, do not move the vehicle with the air suspension deflated. Doing so could result in a loss of vehicle control, possibly causing personal injury and property damage.
Note: Chassis built with an air suspension dump option have an automatic feature that will not allow the suspension to be deflated unless the parking brakes are set. The suspension will automatically inflate when the parking brakes are released.
Tag-Axle Suspension—Dump Only
In the TAG DUMP AUTO mode, the axle air bags will deflate when all of the following conditions are met. If any of these conditions are not met, the tag-axle air bags will fill:
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The tag-axle suspension dump switch is momentarily pressed to toggle the tag-axle control module into the dump mode.
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The vehicle speed is less than 8 mph (13 km/h).
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The vehicle is in neutral or a forward gear.
If the vehicle exceeds a speed of 8 mph (13 km/h) while the switch is in the TAG DUMP AUTO position, the tag axle suspension dump switch control system will override the TAG DUMP AUTO mode and the tag suspension air bags will refill.
Important: The tag-axle suspension dump switch feature must be cycled on and off of the TAG DUMP AUTO position if an override event occurs while the switch is in the TAG DUMP AUTO position.
In the MANUAL mode, the axle air bags will deflate when all of the following conditions are met. If any of these conditions are not met, the tag-axle air bags will fill:
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The tag-axle suspension dump switch remains in the MANUAL mode (reverse maintained position).
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The vehicle speed is less than 8 mph (13 km/h).
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The MANUAL mode portion of the switch is pressed a second time to exit MANUAL mode.
Tag-Axle Suspension—Dump and Tag Wheel Steering
The tag-axle will be locked in an unsteerable position when any of the following conditions are met:
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The vehicle is in reverse.
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The vehicle speed exceeds 20 mph (32 km/h) while accelerating or exceeds 15 mph (24 km/h) while decelerating.
The tag-axle will be unlocked and steerable when all of the following conditions are met:
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The vehicle is in a forward gear.
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The vehicle speed is less than 20 mph (32 km/h) while accelerating or less than 15 mph (24 km/h) while decelerating.