Solid Axle Swaps Explained

Solid Axle Swaps Explained

A lot of the questions we get from customers are about our Barnes 4WD Solid Axle Swap Kits. These kits are some of Barnes 4WD best sellers. The foundation of my Average Joe knowledge can be credited to these kits. Much like if your swapping axles in a leaf sprung rig you should make one of these kits your foundation!  

Barnes 4WD offers a lot of premade kits. These are excellent time savers, but a lot of Barnes 4WD customers call needing just one or two parts and not an entire kit. So, let’s break down these kits piece by piece. Average Joe Style! 

If you’re thinking about putting a new axle under a rig with leaf springs, or just replacing existing parts. The main measurements you’ll need to know will be axle tube diameter, leaf spring width, shock mounting width and U-bolt length. 

Barnes 4WD Solid Axle Swap Kits Consists of 4 main components, all of which can be ordered individually.


  1.    Anti-Wrap Spring Perches

 So, what is a spring perch? A spring perch is going to be welded on your axle tube. This allows a place for your springs to set and be located by the center pin of your spring pack.  

 To get the correct spring perch for your application. The main questions you’ll need answers to will be. 

What is my Leaf Spring Width? 

To get the correct measurement here all you’ll need to do is grab your favorite tape measure, go to your leaf springs and measure across the leaf spring. The best place to pull this measurement will be across the spring that is going to contact the spring perch.   


What is my Axle tube Diameter? 

Finding the correct measurement here is again a very simple process. Grab a set of calipers and measure the outside diameter of your axle tube.

If you don’t have a set of calipers handy, just wrap your tape measure around the axle tube and get the circumference. Then divide by 3.1456 AKA pi.


If you’re just looking for spring perches, you now have all the information you’ll need. Click here to view Barnes 4WD Anti-Wrap Spring Perches. 


  1. U- Bolt Plates

U-bolt plates are the components that will set on the top of your springs, and allow for the U-bolts to be bolted in.

To get the correct U Bolt Plates for your application, you’ll only need to know 3 measurements.

Leaf Spring Width and Axle Tube Diameter which can be determined the same way as it was for the spring perches.

The only other measurement that you’ll need to know would be the diameter of your U-bolts. That’s if you’re not replacing the original U-bolts. Our U-bolts all have a diameter of 5/8.  This will be same as our top plates. We always recommend replacing U-bolts when swapping axles. U-Bolts are designed to be used only one time. We’ll get more into how to measure the diameter of your U-bolts below. 

  1. U-Bolts 

U-bolts are just that, a u-shaped bolt that will fit around your axle tube and be bolted to your U-Bolt Plates.  The biggest misconception with U-bolts is that they are all the same; this could not be farther from the truth. We feel that U-Bolts are the most important component of a leaf spring suspension and this is why we are so meticulous about the specifications of our U-bolts.

The measurements you’ll need to know here are going to be.

U-bolts diameter. All of our U-Bolts Measure 5/8 diameter. This refers to the diameter of the legs of the U-Bolt.  To measure your U-bolt diameter, grab some calibers and measure at the threaded portion of the U-bolt. 

Next is U-Bolt length the best way to get this measurement is to measure the U-bolts you’ll be replacing. You’ll want to measure the length from the top of the arc to the end of the U-bolt.  

The final measurement you’ll need to know to get the correct U-bolts are axle tube diameter. Of course, you can measure your axle tube to get the diameter. But if you have the U-Bolts you’re replacing all you need to do is measure the distance between the legs. 

  1. Shock Mounts

      The measurements you’ll need to know here will be the mounting width of your shock. You can get this measurement by measuring the inside width of your shock bracket where the bolt goes through. 

     The last measurement you’ll need will be the bolt hole size you’ll need for the shock. You can do this by measuring the bolt you removed from your shock or by measuring the size of the hole that runs through the shock. 


With these measurements you can now successfully piece together your own Solid Axle Swap Kit.