Measuring to Determine the Correct Replacement Pin Box for a 5th-Wheel Trailer

If you cannot locate the OEM pin box manufacturer's name and model number of your trailer's 5th wheel king pin box, you can measure it to find a correct replacement.

Ultra Fab replacement pin box5th Airborne replacement pin box

Step 1.

First, select the pin box style from the drawings below that matches the pin box on your 5th wheel trailer.

Diagram of the 5 styles of pin boxes

Step 2.

Next, after you have selected your pin box style, "Click" on the drawing below that matches it. Then print out the drawing and take it to your trailer. Use the drawing to measure the horizontal bolt hole distance, vertical bolt hole distance, bolt size, bolt head size, front row of bolts to king pin, back row of bolts to king pin and pin box width. Also, record the number of bolts per side that secure the pin box to the trailer frame.

Click on your pin box style to access a printable full size drawing.

Diagram of short pin box

Click to Enlarge

Diagram of medium pin box

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Diagram of long pin box

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Diagram of telescoping 45 degree pin box

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Diagram of telescoping 72 degree pin box

Click to Enlarge

Step 3.

Finally, use the pin box measurement chart to match the measurements of your trailer's OEM pin box to the manufacturer and model number. This will be the proper replacement pin box for your 5th wheel.

Note: Extending a pin box increases the amount of leverage applied to the frame of a 5th wheel trailer. Because this increased leverage can cause damage to a trailer frame, trailer manufacturers might not honor the trailer warranty if the pin box has been extended. Check with your trailer manufacturer if a new pin box will add more than 6" to the length of your original.

Pin Box Measurements
OEM Pin BoxHorizontalVerticalCenterBolt SizeBolt head SizeBolt Qty per SideFront Row to King PinBack Row to King PinPin Box Width
LongFabex 665,
M&M 665
7-5/8", 7-7/8"2"N/A1/2"3/4"418-3/4"26-3/8"12"
Venture CJ20515...178"1-1/2"N/A1/2"3/4"18-1/2"26-1/2"12"
Steelco/Davis PB02,PB02W8"1-1/2"N/A1/2"3/4"618-1/2"26-1/2"12"
Fabex 7659-1/2"2"4.75"5/8"15/16"321-1/2"31"12-1/2"
Fabex 7509-1/2"2"4.75"5/8"15/16"316"25-1/2"12-1/2"
RBW 70289-1/2"2-1/2"N/A5/8"15/16"220"29-1/2"12-1/2"
Lippert 16217-7/8"2"N/A5/8"15/16"617-3/4"25-5/8"12"
Lippert 1621 HD7-7/8"2"N/A5/8"15/16"617-3/4"25-5/8"12"
Fabex 5009-1/2"2-1/2"N/A5/8"15/16"220"29-1/2"12-1/2"
Fabex 5039-1/2"2-1/2"N/A5/8"15/16"218"27-1/2"12-1/2"
Lippert 17168-3/4"2-1/2"N/A5/8"15/16"920-3/8"29-1/8"12-1/2"
Leland 79207"1-1/2"N/A1/2"3/4"621"28"14"
Youngs Welding9"3"N/A3/4"1-1/8"420"29"12"
MediumFabex 7309-1/2"2-1/2"4-3/4"5/8"15/16"310-1/2"20"12-1/2"
RBW 70199-1/2"2"N/A5/8"15/16"213"22-1/2"12-1/2"
Lippert 07197-7/8"2"N/A5/8"15/16"69"16-7/8"12"
Fabex 5209-1/2"2-1/2"N/A5/8"15/16"213-1/2"23"12-1/2"
Fabex 5309-1/2"2-1/2"N/A5/8"15/16"211"20-1/2"12-1/2"
Leland 79107"1-1/2"N/A1/2"3/4"69"16"14"
Youngs Welding9"3"N/A3/4"1-1/8"48"17"12"
Lippert 11168-3/4"2-1/2"4-3/8"5/8"15/16"914-5/8"22-3/8"12-1/2"
Fabex 663,
M&M 663
Venture CJ13515,
Steelco/Davis PB018"1-1/2"N/A1/2"3/4"69-3/4"17-3/4"12"
45 degrees
Youngs Welding Tube Style 7-1/8"2-1/8" N/A1/2" or 5/8"3/4" or 15/16" 5 (Retracted)0" 10-3/4"8"
72 degrees
Atwood AB-727-7/8"2"N/A1/2"3/4"4 (Retracted)-1"6-7/8"12"
RBW 7016-2P7-1/4"2"N/A3/4"1-1/8"2 (Retracted)-1"6-1/4"12"
ShortFabex 5609-1/2"2-1/2"N/A5/8"15/16"61-1/2"11"12"
Lippert 01158-3/4"2-1/2"N/A5/8"15/16"91-1/2"10-1/8"12-1/2"

Updated by: Raymond P.

Last updated: 7/5/18

Questions and Comments about this Article

Ron S.

Thank You for this illustration. Bought a used fifth wheel that had a Reese Side Winder pin box on it, want to replace it with a pin box with a shock absorber and air cushion in it. This will certainly help to find the correct replacement pin box.?? I hope!! 81906

Reply from Chris R.

Great! Just let us know if any questions come up. 67289

Reply from Chris R.

@RonS I may want to buy your sidewinder.... Email me at [email protected] if interested 67916



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