Engineering Tip #11: Check Your Power Plant Frame

Miata racers should check the alignment of this critical component to aid drivetrain longevity

Miata owners and racers know their cars are special, and one of the items that makes Miatas of all generations unique is the Power Plant Frame – that ladder tying the drivetrain together, minimizing component movement relative to each other. Outside of the Power Plant Frame, the only places the drivetrain is mounted to the car are the engine mounts and the differential mounts, which means the alignment of the Power Plant Frame, or PPF, is absolutely critical.

“The Power Plant Frame ties the drivetrain together,” explains Brian Falcon, a racing and shop mechanic for Winding Road Racing, which means he has worked on a variety of Miata race cars, especially the ND Global Mazda MX-5 Cup car and the NC-based Spec MX-5 Challenge cars. “There’s not a hard mount for the transmission, so the angle of the Power Plant Frame is critical for the function and longevity of drivetrain components. If you don’t set the angle properly when you install it, it can lead to premature gearbox failure, diff failure … just a snowball effect of parts failures throughout your entire drivetrain.”

Before any of that happens, misalignment can lead to interesting noises and vibrations. Those are the first signs that something is amiss with the PPF. Fortunately, proper alignment isn’t a terribly difficult task, requiring only a straight edge, a ruler or calipers, the tools to loosen and tighten the bolts, and a jack. The jack will lift the PPF for you while you check the measurements and tighten the bolts. And, of course, make sure those bolts are torqued properly.

“It’s just taking your time, making sure you do it right,” Falcon says. “Double check everything – there are a lot of moving parts down there. You want to make sure everything is torqued and put eyeballs on all the different mounts, because it’s not just the PPF – you need to make sure that your diff and motor mounts are in good order because everything works in unison. So if you have one part that’s fatigued or failing, it could cause a failure somewhere else down the line.”

If you have odd vibrations or noises in your drivetrain, or find yourself replacing components more often than you think you should, a misaligned Power Plant Frame could be the culprit.