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How to Determine Correct Height Setting on Demco Hijacker Autoslide

Question:

How do I determine the set height for my hitch. Read on your page about measuring the bed floor height to ground 39”. And pin box to ground 47”. That puts me at 8” difference but will that give me that 6” clearance I need for the bed rails?

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Helpful Expert Reply:

Thank you for providing those measurements!

Since your 5th wheel hitch height is 47 inches, subtracting the bed height of 39 inches gives us the 8 inches you mentioned which is technically the setting you would need to use on your Demco Hijacker Autoslide # DM8550034. This poses a problem since the HIjacker is limited to a height adjustable from 15-1/4 to 18 inches tall. If your measurements are correct, this means that in order to tow your 5th wheel trailer with your 2019 GMC Sierra 2500 and Demco Hijacker, your trailer will need to be raised 7-1/4 inches, which is quite unusual and will definitely not give you the 5-6 inches of clearance needed between the top of your bed rails and the bottom of the trailer loft.

When measuring your 5th wheel, make sure you're measuring from the ground to the bottom of the skid plate of your pin box, not to the king pin, as shown in the attached diagram. I suggest using a level like # WM6780 to ensure you're getting the most accurate measurement.

Most pin boxes are adjustable as well so make sure you've got yours to the highest possible setting.

The next option is to raise your trailer with an over/under kit like # K71-385-00 which is for 3 inch round axles and allows you to flip the springs above the axle to gain ground clearance. The amount of inches you gain is determined by the diameter of the axle and the stack height of your leaf springs.

If after doing all this you find that your 5th wheel pin box height is still under 54 inches, you may need to either go with a different trailer, a different 5th wheel hitch or depending on how close you can get the trailer and hitch to be level, tow it outside of the recommended leveling specs.

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