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

What years do these air springs and level valves fit, and are they compatible with both 357 and 378 models?

Our air springs and level valves are designed to fit Peterbilt 357 and 378 models from 1987 through 2007. While many components are interchangeable between the 357 and 378, some level valve mounting brackets and linkage configurations differ based on suspension type (Hendrickson, Reyco, or Peterbilt Air Leaf). Always verify your specific suspension model before ordering, as cab-over-engine (COE) variants may require different components than conventional models.

How do I know if I need to replace my level valve or just the air spring?

If your truck leans to one side or takes excessive time to level out after loading, start by checking for air leaks at the spring using soapy water. A deflated air spring that won't hold air needs replacement. However, if the spring holds air but the truck won't maintain proper ride height or constantly adjusts up and down, your level valve likely needs replacement. Common level valve symptoms include delayed height adjustment (more than 15-20 seconds) or continuous air cycling even when parked on level ground.

What tools and experience level are needed to install these components?

Air spring replacement requires basic hand tools, jack stands, and approximately 1-2 hours per side for experienced mechanics. Level valve installation is more complex, requiring proper linkage adjustment and ride height setting. You'll need a measuring tape, angle finder, and air pressure gauge. While air springs are a moderate DIY job, level valve installation often requires experience with suspension geometry. Improper level valve adjustment can cause premature air spring failure or unsafe ride characteristics.

What's the difference between OEM and aftermarket air springs, and how long should they last?

OEM Firestone and Goodyear air springs typically last 300,000-500,000 miles under normal conditions. Aftermarket options from Continental ContiTech or Firestone's Ride-Rite series offer similar durability at 20-30% less cost. The main differences are in rubber compound quality and crimped end construction. Premium springs feature multi-ply construction and reinforced bead plates. In harsh climates or severe-duty applications, expect 30-40% shorter lifespan. Always replace air springs in pairs to maintain balanced suspension performance.

Why does my truck still ride rough after replacing air springs and level valves?

New components require proper adjustment and system calibration. First, verify correct ride height settings - typically 11.5 to 12 inches from frame to axle on most 357/378 models. Check that level valve linkage moves freely without binding and maintains proper angle (usually 0-5 degrees from horizontal when at ride height). Rough ride can also indicate worn shock absorbers, incorrect air pressure settings, or damaged height control valve linkages. Some drivers report improved ride quality after adding supplemental air tanks to increase system volume.