1988-2007

The Peterbilt 378 is a Class 8 vocational and highway-capable conventional truck, produced from the late 1980s through the mid-2000s. It was known for combining the durability needed for heavy-duty work with the comfort and options required for long-haul trucking. The 378 became a popular choice for fleets and owner-operators who needed versatility in both on-road and vocational settings.

The Peterbilt 378 was widely used for:

• Dump trucks
• Heavy haul and lowboy applications
• Long-haul trucking
• Flatbed freight
• Mixer trucks
• Tanker and fuel delivery
• Oilfield support

Its set-forward axle option made it especially well-suited for bridge-formula compliance in many U.S. states.

Cab Type

• Cab Style: Conventional narrow-body
• Cab Width: Approximately 1.9 meters (75 inches)
• Available in day cab, flat top sleeper, and raised roof sleeper configurations
• Shares the same cab shell as the 375, 377, 379, and 385 (narrow cab models)

Aftermarket Seat Compatibility

The Peterbilt 378 uses the standard vocational/narrow-body seat bolt pattern: 4.68" x 12"

Most aftermarket seats will bolt in directly with no adaptor required.

Installation Notes

• No adaptor needed for most seat replacements
• On sleeper cabs, ensure there's enough vertical clearance if using high-travel suspension seats
• Some 378s may have aftermarket risers or shims—remove these if upgrading to a taller seat