XPOLogistics Manufacturing
Upper Coupler Maintenance Recommendations
August 16, 2018

The trailer upper coupler must be properly maintained and inspected to ensure proper function
with the fifth wheel. The procedure outlined herein is for inspecting kingpings that conform to
SAE J700 specifications and are subject to the wear limits of SAE J2228. Kingpin inspection
should be conducted every three months or 30,000 miles to ensure proper function. Each of
the inspection steps listed below should be performed front-to-back and side-to-side.
1. Inspect the upper coupler for damage.
Check for nicks, gouges, cracks, deformations, missing fasteners and any other damage
that could interfere with or affect safe operation. Replace the entire upper coupler if
any damage is found. If no damage is found, move on to the next step.
2. Inspect the flatness of the bottom plate.
Using the XPO Upper Coupler Gauge check to see if the bottom plate of the upper
coupler is warped (see Figure 1). Slide the gauge over the center of the kingpin spool
with the 1/8” tall ribs touching the bottom plate. If both ribs touch the bottom plate
and the gauge does not rock back and forth, move on to the next step.

There should be no contact here.
Gap to bottom plate should not exceed 3/16”

Figure 1

2001 S. Benton Street, Searcy, AR 72143
Phone 501-279-0991

3. Inspect the kingpin spool for straightness.
Using the XPO Upper Coupler Gauge or a square check to see if the kingpin is bent. The
kingpin should not exceed 1ᵒ from square in any direction. A bent kingpin accelerates
lock wear and may interfere with the locking mechanism. A kingpin that is more than 1ᵒ
out of square will require that the entire upper coupler be replaced. If the kingpin is
found to be within 1ᵒ of square, move on to the next step.
4. Inspect the kingpin spool for proper length.
Using the XPO Upper Coupler Gauge check the length of the kingpin spool (see Figure
2). If the end of the gauge does not easily fit the profile of the kingpin spool then the
spool is not of the proper length and the upper coupler should be replaced. If the gauge
easily matches the side of the spool, move on to the next step.

Figure 2

5. Inspect the kingpin spool for wear.
Using the XPO Upper Coupler Gauge check the wear on the 2.00” and 2.88” diameter
sections of the kingpin spool (see Figures 3 and 4). The gauge will indicate more than
1/8” of wear if the appropriate diameter section of the kingpin spool enters the slotted
section of the gauge (see Figure 5). If the spool slides into the slot on the gauge the
spool has exceeded the maximum amount of wear and the entire upper coupler should
be replaced. If the spool will not fit into the slot on the gauge the wear limits have not
been reached and the upper coupler is safe to continue using.

2001 S. Benton Street, Searcy, AR 72143
Phone 501-279-0991

Figure 3

Figure 4

2001 S. Benton Street, Searcy, AR 72143
Phone 501-279-0991

2.88” Diameter

Figure 5

2001 S. Benton Street, Searcy, AR 72143
Phone 501-279-0991

2.00” Diameter