As a Diesel Power reader, it's likely you have a big truck with big tires, a big suspension lift, and a big, bombed-out diesel engine. But when it comes time to honk at someone, you're stuck with that wimpy factory-installed horn. Not only is this unacceptable for your big truck, but it can also be a safety and theft concern that's easily preventable.
Why Train Horns?In some parts of the country, the idea of adding train horns to trucks has been around for several years. In fact, there's a whole industry that has popped up offering these kits. To some, installing powerful horns on a daily driver may seem excessive, but if you're pulling a 15,000-pound trailer and you see a car about to pull in front of you, a simple warning blast can mean the difference between the driver noticing or hitting your rig.
Another important benefit is theft prevention. Most new trucks come equipped with factory alarms that sound the horn, so a train horn setup can become a powerful deterrent. Let's face it, when we're in a shopping mall and hear a typical car alarm, people barely notice. Thieves count on this to make their lives easy as they get away with the stolen vehicle. After hearing one blast from a train horn, we can almost guarantee it will send any would-be thief looking for another target.
Before beginning this project, review all the parts included in the kit and become familiar with the components and their purposes in the final install. | 
Perhaps the most important step is to find a good location to mount the horns, compressor, and tank; each vehicle will be different in this regard. On our '06 Dodge Ram 2500, we mounted the compressor on the outside of the framerail on the passenger side of the truck. A solid mount will prevent vibration and other problems down the road. | 
The best way to mount the air tank to the frame was to use a template to transfer the location of the mounting holes. The compressor needs to be close enough to the air tank for the braided line to reach, so test-fit your planned locations before drilling holes. |
We mounted the air tank to the frame using corrosion-resistant bolts and secured them with lock washers. Each application will be different, and the kit doesn't include the bolts. We used 51/416x3-inch bolts to pass through the framerails. | 
This compressor pressurizes the tank and supply lines to 150 psi, so it was critical that all the brass fittings were wrapped with Teflon tape. Without tight fittings, the system will leak and result in compressor overuse. | 
The air tank was connected to the compressor using the attached braided airline. This hose shouldn't be modified or extended. |
We fabricated this simple bracket out of bar-stock steel to support the air horns. Due to space limitations, we mounted the horns as two sets of two on the outside of each framerail. | 
We then attached the pressure valve to the air tank. We left the wires disconnected and dealt with the 12-volt connections at the end. | 
Using the fabricated brackets, we attached the horns between the body of the truck and the framerails. We used long bolts on the frame side and attached the other end of our horn-mounting brackets to the inside of the body using sheetmetal screws. |