What Causes a Dump Truck to Miss and Slam?

Red dump truck cylinder

Standard Operation for a Telescopic Cylinder

To explain what causes miss and slam during telescopic cylinder function, let’s first review the standard operation for a telescopic cylinder.

Telescopic hydraulic cylinders feature a series of steel tubes, called stages, that are nested inside each other. Most standard telescopic cylinders feature anywhere from 2 to 5 stages. This design allows for a significantly longer extension stroke than standard hydraulic cylinders, which is why they are used on dumper truck bodies.

Once the hydraulic system introduces pressure, the largest sleeve or tube moves first, then the next largest, down to the smallest sleeve or plunger. When retracting the cylinder, the smallest sleeve or plunger closes or collapses first, then the next largest sleeve, up to the largest sleeve.


When a dumper truck bed slams down, it’s usually due to missed stages. This issue, known as Mis-Staging, occurs when the cylinder does not extend or retract in the correct sequences as described above.

Here’s what dump truck Mis-Staging can look like with a 3-stage cylinder: the largest sleeve extends properly, but the plunger starts extending before the middle (or next larger) sleeve starts to extend. The middle sleeve finally breaks loose and shoots out, causing it and the plunger to collapse or drop back into the cylinder. This creates a loud banging noise as the dump truck cylinder slams down.


There are several reasons the dump truck cylinder may be missing stages of the extension or retraction operation:

  1. The sleeve’s Pack/Seal or Bearing is not moving or may be too tight, prohibiting the sleeve from extending or retracting in the proper sequence.
  2. The Cylinder that the body or unit is mounted in may have a worn or damaged part. This causes the cylinder to sideload, not allowing the sleeve to extend or retract in the correct order.
  3. A bent, egg-shaped, or bulging sleeve can cause tightness, resulting in the sleeve being unable to extend or retract appropriately.

Regularly inspecting your dump truck cylinders can help you catch these and other issues before they become a big problem. Check for loose connections and signs of bending or building on your sleeve. Seals should also be checked regularly and repacked as needed. Bleeding cylinders weekly is another way to keep things operating smoothly.

Only Use High-Quality Cylinders in Your Dump Truck

Hydraulic Cylinders, Inc. supplies single- and double-acting telescopic hydraulic cylinders manufactured and assembled in the USA. We offer a full line of standard products and manufacture custom cylinders to meet your performance needs. Our performance-built cylinders are made to last and withstand your most challenging applications.

Several factors go into choosing a telescopic cylinder for your dump truck. Our team is here to help you find the best solutions for your dump truck. Send a quick message or give us a call at 1-866-818-0195 to discuss your requirements.

Related Blogs