15 steps on how to slide tandems on a semi-trailer

Sliding the tandem axle group along a trailer to adjust the weight distribution on each axle group is a common practice for most truck drivers.

Knowing how to slide tandems on a semi-trailer and how to do it safely is an essential part of a truck driver’s job.

Why truck drivers should know how to slide tandems

There are a few reasons why most truck drivers should know how to properly slide the tandems on a semi-trailer:

• To ensure the overall weight of their tractor-trailer is distributed in the best way possible.
• To meet the legal requirements of the states in which they drive.
• To comply with regulations governing how far back or forward trailer tandems can be moved (also known as the distance between the kingpin on the trailer and the trailer’s tandem axle group).

How to distribute weight on a tractor-trailer

It is important for truck drivers to understand the positions of the axles on a tractor-trailer. Axles are a contributing factor to whether a driver hauls a load safely and legally.

Most tandem axles can be moved forward and backward along the length of the trailer to ensure proper weight distribution on the tractor and trailer axles.

Many semi-trailers have sliding tandem axles that are mounted directly on the frame rails under the trailer. When the weight of a load being hauled is unbalanced, a driver has two options:

• Transfer weight to the tractor by sliding the axles of the trailer back.
• Transfer weight to the trailer by sliding the axles of the trailer forward.

Each tandem hole accounts for approximately 250 pounds of weight transfer, which means:

• If you move the tandems back by one hole, you transfer 250 pounds to the tractor axles.
• If you move the tandems forward by one hole, you add 250 pounds to the trailer.

How to slide tandems on a semi-trailer

There are 15 basic steps to safely sliding tandems:

1. Ensure the tractor and trailer are straight.
2. Set the parking brakes of the tractor and trailer.
3. Make sure air pressure is at maximum.
4. Lock the power divider for maximum traction. 
5. Activate the Trailer Hold Switch (also known as the Trailer Spring Brake Override Switch).
6. Pull the slider handle out. Lock in the retainer. 
7. Mark the hole you want the front locking pin to land.
8. Shift the transmission into reverse. If operating a manual transmission truck, be sure the range selector is down (Low-Side). 
9. Release just the tractor parking brake by pushing on the yellow button.
10. Back the trailer up. The tandems will remain stationary while the trailer moves. 
11. Set the tractor parking brakes. Safely exit the tractor. Check the position of the front locking pin.
12. If the pin is where you want it, remove the slider-locking handle from its retainer. Allow the handle to go in. 
13. Shift into Drive (second for manual) or Reverse and rock the trailer gently to ensure the locking pins are firmly seated and completely through the holes.
14. Visually inspect that the pins are through the holes and the locking handle is all the way in. 
15. Unlock the power divider and deactivate the Trailer Hold Switch (also known as the Trailer Spring Brake Override Switch).

Please note this is an example of how to slide tandems on a semi-trailer. It is important to remember the type of driver you are, the company you work for and the type of truck you drive can impact how you slide tandems on a semi-trailer. Be sure to consult your company guidelines or speak with your leader for more information about sliding tandems.