FLAT LINE PARTS

Fleet-Grade Truck Parts

Fleet-grade truck parts, shipped fast.

Spec-matched, inspected, and ready to roll — the parts your trucks need, from a supplier that picks up the phone.

Trusted by 2,400+ fleets

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100+Parts in Stock
5Categories
2,400+Fleets Served
24hrQuote Turnaround

Fleet-grade parts
Fast tracked shipping
Trusted by 2,400+ fleets

Shop by Category

Five categories. One trusted supplier.

Maintenance

Filters, fluids & service parts

Performance

Tuners, drivetrain & engine upgrades

Lighting

LED bars, headlights & electrical

Interior

Seats, trim & cab accessories

Accessories

Chrome, trim & exterior dress-up

Best Sellers

Built for the long haul.

FleetStop Heavy-Duty Brake Kit

FleetStop Heavy-Duty Brake Kit

Drum, shoes, and hardware kit rated for steer and drive axles.

Synthetic Diesel Engine Oil 15W-40

Synthetic Diesel Engine Oil 15W-40

5-gallon pail of synthetic-blend oil for extended drain intervals.

Engine Performance Tuner

Engine Performance Tuner

Plug-and-play diesel tuner for horsepower, torque, and economy.

Heavy-Duty Clutch Assembly

Heavy-Duty Clutch Assembly

OEM-grade clutch assembly for class 8 high-torque drivetrains.

Apex 22" LED Light Bar

Apex 22" LED Light Bar

Flood-pattern 22-inch LED light bar with IP68 housing and dual-row optics.

FleetPro Premium Driver Seat

FleetPro Premium Driver Seat

Air-ride driver seat with heated cushions and lumbar support.

Hadley Air / Train Horn Kit

Hadley Air / Train Horn Kit

Loud, attention-getting air horn kit with compressor and tank.

Chrome Front Bumper

Chrome Front Bumper

Polished chrome front bumper with bolt-on installation.

We Carry Leading Brands

The names fleets already trust.

OEM and aftermarket parts from the manufacturers that built the industry — stocked and ready to ship.

BendixGatesTruck-LiteGroteDonaldsonFleetguardPacbrakeMeritorHaldexSKFWabco

From the Garage

Guides, tips, and field-tested know-how.

How to Install LED Headlights on a Heavy-Duty Truck

A step-by-step walkthrough for swapping halogen headlights for LED assemblies on Class 6–8 trucks, including wiring, sealing, and aiming.

Air Filter Maintenance: When to Replace and Why It Matters

A practical maintenance schedule for air filters across duty cycles, plus the symptoms that tell you a filter is past its service life.

Performance Brake Pads vs. Standard: Which Is Right for Your Fleet?

Comparing friction materials, rotor wear, and total cost of ownership between standard and performance brake pads for fleet use.

Five Signs Your Suspension Bushings Need Replacement

How to spot worn suspension bushings before they cause uneven tire wear, alignment drift, or a handling complaint from a driver.

Why Choose Us

Why fleets choose Flat Line Parts.

Quality Parts

Fleet-grade OEM & aftermarket components.

Fast Shipping

Same-day dispatch on in-stock orders.

Expert Support

Real parts specialists on the phone.

Easy Returns

30-day hassle-free returns, no restocking fee.

How It Works

From spec to shipped in three steps.

01

Browse Parts

Explore 80+ parts across 5 categories.

02

Request a Quote

Tell us what you need — we reply within 24 hours.

03

Get Your Parts

Same-day dispatch, delivered to your door.

Frequently Asked Questions

Answers before you ask.

In-stock orders placed before 2pm ET ship the same day via standard ground freight. Most orders arrive within 3-5 business days; expedited freight is available at checkout for time-critical repairs.

Fast shipping nationwide
30-day returns
OEM & aftermarket quality

Ready to upgrade your fleet?

Tell us what you need. A parts specialist replies within 24 hours with pricing, availability, and lead times.

Request a Quote