Frequently Asked Questions About Peterbilt 357/378 Fan Blades & Shrouds

Will these fan blades and shrouds fit my specific year Peterbilt 357 or 378?

Most fan blades and shrouds for Peterbilt 357/378 models are compatible with trucks manufactured from 1987 through 2007. However, there are variations based on engine type (Cat, Cummins, or Detroit) and radiator configuration. Before ordering, check your current fan blade diameter and mounting bolt pattern. The most common sizes are 24", 26", and 28" diameter blades. For exact fitment, have your VIN and engine serial number ready when contacting us.

What's the difference between steel and composite fan blades, and which should I choose?

Steel fan blades are more durable and better suited for severe-duty applications or trucks that idle frequently. They typically last 5-7 years but are heavier and noisier. Composite (fiberglass or nylon) blades are 40-60% lighter, reducing strain on your fan clutch and improving fuel economy by 1-2%. They're quieter but may need replacement every 3-4 years. Choose steel for heavy hauling or frequent PTO use; choose composite for highway driving and better fuel efficiency.

Do I need to replace my fan shroud when changing the fan blade?

Not necessarily, but it's recommended to inspect your shroud whenever replacing the blade. A damaged or improperly fitted shroud reduces cooling efficiency by up to 30%. Check for cracks, broken mounting tabs, or gaps larger than 1 inch between the blade tips and shroud opening. If your shroud is intact and the new blade maintains proper clearance (typically 0.5" to 1" all around), you can keep your existing shroud.

What tools and time are required for installation?

Installation typically takes 45-90 minutes with basic hand tools: socket set (usually 9/16" and 5/8"), torque wrench, and safety equipment. You'll need to drain some coolant if removing the radiator-mounted shroud. Key steps include: disconnecting the battery, removing the upper radiator hose (for some models), unbolting the old fan from the clutch hub, and torquing new blade bolts to 35-45 ft-lbs. Always check blade clearance before starting the engine. Professional installation runs $75-150 if you prefer not to DIY.

How do I know if I need a standard or reverse rotation fan blade?

This is critical - installing the wrong rotation blade can cause engine overheating and damage. Most Peterbilt 357/378 trucks use standard rotation (clockwise when viewing from front), but some specialized applications use reverse rotation. Check your current blade for rotation arrows or markings. If unmarked, look at the blade angle - the curved edge should scoop air toward the engine when rotating. When in doubt, provide your engine model and serial number, as rotation is determined by your engine's water pump design.