Peterbilt 357/378 Air Springs & Level Valves

Frequently Asked Questions About Peterbilt 357/378 Air Springs & Level Valves

What do air springs and level valves actually do on my Peterbilt 357/378?

Air springs (also called air bags) are part of the suspension system, supporting the weight of the truck and cab while absorbing road shock for a smoother ride. Level valves work alongside the air springs to automatically adjust air pressure and maintain proper ride height as load conditions change. Together, these components help stabilize the suspension, reduce wear on other chassis parts, and keep the truck riding level whether it is loaded or empty.

How do I know if my air springs or level valve need to be replaced?

Common signs of a failing air spring include visible cracks, bulges, or leaks in the rubber bellows, a sagging cab or axle, or a noticeable decrease in ride quality. A malfunctioning level valve often causes the suspension to sit unevenly, respond slowly to load changes, or fail to hold ride height at all. If you notice unusual bouncing, leaning, or air leaks near the suspension or cab mounts, it is a good idea to inspect these components.

Will these air springs and level valves fit my specific Peterbilt 357 or 378 model?

Fitment can vary based on the year, suspension type, and whether the part is for the cab or chassis. Before purchasing, check the listed specifications, part numbers, and OEM cross-references for each product to confirm it matches your truck's configuration. If you are unsure, having your VIN or existing part number on hand will make it easier to verify compatibility with our team.

Can I install a replacement air spring or level valve myself, or should I have a professional do it?

Many experienced truck owners and mechanics are able to replace air springs and level valves with standard tools, especially if they are familiar with the existing setup. However, because these parts affect ride height, weight distribution, and overall suspension performance, improper installation can lead to uneven handling or premature part failure. If you are not confident in diagnosing or adjusting the suspension system afterward, having a qualified technician handle the installation is recommended.

Are aftermarket air springs and level valves as reliable as OEM parts?

Quality aftermarket air springs and level valves are manufactured to match OEM specifications and can offer comparable performance and durability, often at a lower cost. That said, build quality can vary between brands, so it is worth reviewing product details, materials, and any included warranty information before making a decision. Choosing a reputable brand helps ensure the part performs consistently under normal operating conditions.