Axle Over-Under Kits for Raising Height of 5th Wheel Trailer for Better Clearance at Truck Bed Rails

Question:

I have a 25 ft vanguard legend 5th wheel. I was towing it with a 2007 f350, but it got stolen. The rear of the trailer dragged when backing into my driveway, and it sits nose high when being towed. I now have a 2017 F350 and the rear of the trailer seems to sit even lower. I’ll know tonight when I push it in the driveway. Will a over under conversion kit work well to raise the trailer? I’m fairly mechanically inclined and have no problem tackling the job myself. I’ve read some reviews and it seems fairly straight forward. The trailer has two axles so i guess I need 2 kits. Seems trailer sway could be an issue after the fact but I seem a lot of newer trailers that sit a lot higher off their axles when tower and it doesn’t seem to be a problem. What are your thoughts? Will two of your kits be sufficient and safe?

asked by: Mike B

Expert Reply:

Axle over-under kits # K71-385-00 (for 3-inch diameter axles) and # K71-384-00 (for 2-3/8-inch diameter axles are by far the simplest and least costly method to raise the height of a 5th wheel trailer. Late model trucks do seem to be growing taller and your 2017 F-350 has particularly high bed rails that can make it tough to keep your hitched trailer level. Add large tires and things can get worse.

Sometimes along with installation of over-under kits (and yes, you would need two kits of the size required for your axle diameter) adjustment of the pin box mounting height on the trailer wings is called for.

You are correct that raising the trailer's center of gravity can tend to worsen any existing sway issues or create some. To a degree this can be compensated for if you are able to change your loading scheme for the moveable cargo items in the trailer. Loading as many heavy items as possible in the lowest cargo holds can help a bit. You will also get adjusted to the new feel of the taller trailer with time and a few trips.

The best part is that you can know in advance of installing the kits how much height gain you should see. The lift amount will be the sum of the axle diameter + the height of your leaf spring stacks. So I you have 3-inch axles and 3-inch tall leaf spring stacks you should see about 6-inches of total height gain which is pretty substantial.

The linked diagram shows the recommended minimum clearance dimensions.980

expert reply by: Adam R