Peterbilt 379 Deck Plates & Air Line Boxes

Frequently Asked Questions About Peterbilt 379 Deck Plates & Air Line Boxes

What is the purpose of a deck plate and air line box on a Peterbilt 379?

The deck plate is the flat panel mounted behind the cab, at the front of the frame rails, that provides a surface for routing air lines, electrical lines, and mounting the air line box. The air line box itself organizes and protects the glad-hand fittings and electrical connections that link the tractor to the trailer, keeping them accessible and shielded from road debris.

Will a replacement deck plate or air line box fit my specific Peterbilt 379 without modification?

Most deck plates and air line boxes are built to match factory mounting hole patterns and dimensions for the Peterbilt 379, but slight variations can exist depending on the model year and how your truck was originally optioned. Its a good idea to compare the bolt pattern and overall dimensions of your current setup with the product specifications before ordering, and check for any additional brackets you may need to reuse from your original installation.

What materials are these parts made from, and how do they hold up over time?

Deck plates and air line boxes are commonly available in diamond plate aluminum or stainless steel. Aluminum is lighter and resists rust, while stainless steel tends to offer more durability against dents and impacts, though it adds weight. Both materials are commonly left with a brushed or polished finish, which customers often maintain with regular cleaning to prevent water spots and preserve shine.

Can I install a new deck plate or air line box myself, or do I need a shop to do it?

Many owner-operators replace these parts themselves since installation typically involves unbolting the old unit, transferring or reconnecting air and electrical lines, and bolting on the new piece using existing mounting holes. Basic hand tools are usually sufficient, but if your lines need to be rerouted or lengthened, or if the fit is not a direct match, having a shop handle the install can save time and avoid air line damage.

How do I know if I need just the deck plate, just the air line box, or both?

If your current deck plate is cracked, bent, or heavily worn but your air line box and fittings are still in good shape, you likely only need to replace the plate. Conversely, if the box housing your glad hands and electrical socket is damaged or missing pieces, you can often replace just that component. Many suppliers sell them separately as well as in matched sets, so check your current hardware condition before deciding.