Peterbilt 375/377 Air Springs & Level Valves

Frequently Asked Questions About Peterbilt 375/377 Air Springs & Level Valves

What do air springs and level valves actually do on my Peterbilt 375/377?

Air springs (also called air bags) support the weight of the cab or suspension and absorb road shock by inflating and deflating with compressed air. The level valve works alongside the air springs to automatically regulate air pressure, keeping the cab or axle riding at the correct height as load and road conditions change. Together, these components help maintain a stable, controlled ride and reduce wear on other suspension parts.

How do I know if my air spring or level valve is failing?

Common signs include a sagging or uneven cab or axle height, a rougher than normal ride, visible cracking or bulging on the air spring bellows, audible air leaks near the spring or valve, or the cab settling slowly after the truck sits overnight. If you notice the ride height changing throughout the day or the truck leaning to one side, the level valve linkage or valve itself may need to be inspected.

Will these air springs and level valves fit both the Peterbilt 375 and 377 models?

Fitment can vary by model year, cab configuration, and whether the part is for the cab suspension or axle suspension, so it is important to check the listed specifications and part numbers against your truck before ordering. If you are unsure, having your VIN or the original part number on hand will help confirm the correct match.

Can I replace an air spring or level valve myself, or should I have a shop do it?

Many owner-operators and shops replace these components themselves since the job typically involves supporting the cab or axle, releasing air pressure, and swapping the part with basic hand tools. That said, working around a supported cab or suspension carries real safety risks, so if you are not comfortable safely securing the truck or bleeding the air system, it is worth having a qualified technician handle the installation.

How long should a replacement air spring or level valve last?

Service life depends heavily on mileage, load conditions, road surfaces, and general maintenance, so we avoid quoting a specific lifespan. Regularly inspecting the air springs for cracking, dry rot, or leaks, and checking that the level valve linkage moves freely, will help you catch wear early and get the most life out of the parts.