Jeep SOA and SUA Comparison

Spring over axle and spring under axle suspension are greatly debated by off-road driving enthusiasts. Which version is better?

Whether SOA or SUA will be best for your Jeep will depend entirely on your driving style and preferences.

The following guide will help you to understand the spring under and spring over suspensions.

Understanding SOA

An SOA is a spring over axle conversion. This conversion provides a great amount of lift and is highly beneficial to off-road driving where the terrain is unpredictable or extremely rugged.

SOA conversion is not recommended to be done by DIY enthusiasts. You need a lot of skill and knowledge, plus special tools to do this conversion.

The spring over lift will cost you about twice what the spring under lift costs. The amount of labor required in this lift is much greater than the labor needed for the spring under the lift.

The SOA lift is not highly recommended by suspension experts or mechanics. These lifts can cause your springs to be in a bind and simply fail.

You must have a traction bar in place or your driveshaft is going to need to be lifted off the ground frequently. This type of lift is very hard on the u-joints and will require frequent u-joint changes.

After an SOA conversion, your vehicle is not going to handle normal road travel well. It will become an off-road-only toy. 

You can make these conversions a little at a time as your budget allows.

Understanding SUA

spring under the lift

The spring under suspension is actually more recommended because it lowers the center of gravity and reduces the risk of a rollover accident.

With the spring under axle configuration, the vehicle can travel at higher rates of speed safely. You will also find that spring under the axle creates less stress on the automobile and provides a greater amount of control.

The lift kit may be higher than you would expect, but once you are finished buying all of the new components a spring over requires you will discover the spring under the lift is far less expensive.

The SUA is easier to create and does not require a crossover steering arm. You also do not need a traction bar.

There is a wide variety of ready-to-install kits on the market. The shade tree mechanics and DIY fans will like this type of lift more because they are easier to work with and work on.

You will have to make corrections to the following:

  • Your brake lines
  • The driveshaft
  • The shocks you have

SOA Pros and Cons


  • Greater clearance than the SUA provides
  • If you want 35s or greater this is the right suspension lift for you
  • Can increase on-road handling
  • Off-road handling is greatly improved
  • Articulation is improved
  • Offers a great amount of flex
  • Great for rock crawling adventures


  • More expensive than SUA
  • Requires specialized tools to create the conversion
  • Increases the risk of rollovers because it raises the center of gravity

SUA Pros and Cons


  • Less expensive than SOA
  • Improves the axle control when driving at higher speeds
  • Raises the axle tube
  • Less expensive than a spring over axle conversion
  • Most people can do these lifts without a suspension professional


  • Does not give as high a lift as the spring over axle lift does
  • Does not create the same level of flexibility as spring over axle conversions do
  • Your leaf springs will be more likely to be damaged from debris and obstacles

Frequently Asked Questions

Does SOA Have Greater Flex Than SUA?

Yes. Most people agree that the spring over the axle creates more flex.

Can I Do My Own SOA Conversion?

You need a professional to do this conversion properly.

Is an SOA expensive?

Yes, the components and tools needed to do this type of conversion are expensive.

Final Thoughts

No matter what lift kit style you choose there are going to be drawbacks of some kind. Before you decide to do either a spring over or spring under you need to consider all of the pros and cons, and if you can go speak to a suspension specialist. You never want to make any changes to your vehicle unless you fully comprehend what effects those changes will have on the entire vehicle.

About Brendan Burnett

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