5th Wheel Hitch and Trailer Pin Box Height Adjustment

Question:

I want to lower the pin box to raise the hitch for more clearance. It’s held by two bolts in back of hitch and three bolts in the front. There is an hole below the two bolts for adjustment, but no holes below the three bolts. It appears if I it I’m going to lose one of three bolts for the front. ?? Does that make sense?

asked by: Daren T

Expert Reply:

When a 5th wheel hitch's height is raised to increase clearance between the bottom of the trailer overhang and the tops of the truck's bed rails this can put the trailer into a nose-high orientation. Since trailers tow best when they are level it can be necessary to then also shift the pin box upward on its trailer mounts to restore the trailer to a level stance.

Sometimes adjusting the pin box upward will allow for that extra clearance and still allow the trailer to be close to level when hitched.

When this is NOT the case the trailer's entire suspension can be shifted upward in height to re-level it. The kits that do this are called over-under kits, since they move the axles so they are under the leaf springs instead of above them. The included photo shows this position change for over-under kit # K71-385-00 which works for 3-inch diameter axles; kit # K71-384-00 does the same thing but fits axles that have a diameter of 2-3/8-inches.

These kits raise the trailer height by the sum of the axle diameter plus the height of the leaf spring stack. So, for example, a trailer with 3-inch axles and 2-inch tall leaf spring stacks will see a height gain of approximately 5-inches total when each axle is fitted with kit # K71-385-00.

It is not a good idea to reduce the number of fasteners that hold the trailer's pin box in place; this could result in higher stresses on its frame which might not be covered under warranty.