Frequently Asked Questions About Peterbilt 357/378 Cab Lights

What years do these cab lights fit, and are they compatible with both 357 and 378 models?

These cab lights are designed to fit Peterbilt 357 and 378 models from 1987 through 2007. Both models share the same cab roof design and mounting points, so the lights are fully interchangeable between them. However, always verify your specific truck's configuration, as custom modifications or aftermarket visors may affect fitment.

Do I need to drill new holes for installation, or will these mount to existing factory locations?

Most replacement cab lights are designed to use the factory mounting holes if your truck came with cab lights originally. For trucks without factory cab lights, you will need to drill five evenly spaced holes across the cab roof. We recommend using a template (often included with complete kits) and measuring carefully from the windshield to ensure proper alignment. Professional installation is advised if you're uncomfortable drilling into your cab.

What's the difference between LED and incandescent options, and which should I choose?

LED cab lights draw significantly less power (typically 0.1 amps vs 2 amps per light), last 50,000+ hours compared to 2,000 hours for incandescent, and run cooler. LEDs cost more upfront but eliminate frequent bulb replacements. Incandescent lights provide a traditional warm glow some drivers prefer and are less expensive initially. For daily drivers and commercial use, LED is typically the better long-term investment.

Are the lenses made of glass or plastic, and how durable are they?

Quality cab lights feature polycarbonate lenses, not glass. These impact-resistant plastic lenses are much more durable than glass for over-the-road conditions, resisting chips and cracks from road debris. Look for UV-resistant polycarbonate that won't yellow or fade over time. Cheaper acrylic lenses may crack in extreme temperatures or turn cloudy within a few years.

What wiring modifications are needed, and do these lights work with my truck's existing harness?

Replacement lights typically connect to your existing cab light wiring harness if your truck had factory lights. For new installations, you'll need to run wiring from your clearance light circuit or parking light circuit. Most kits include pigtails that connect to standard two-wire connections (power and ground). LED conversions work with existing wiring but may require different flasher relays if you experience rapid flashing.