Project FD RX7 Restomod: Part 8 – Trans and Diff Mount

Sikky Manufacturing RX-7 HD differential braceTo handle our plans for increased power, we ditch the weak and heavy OEM “Power Plant Frame” (PPF) in favor of a traditional transmission mount from Banzai Racing and differential brace from Sikky Manufacturing.

Mazda RX-7 Power Plant Frame (PPF)Mazda uses a giant, heavy beam they call a “Power Plant Frame” (PPF) to connect the engine, transmission and differential.  This keeps the entire drivetrain as one separate structure that is supported just by the engine and differential mounts.  This design was used on everything from the original MX5 Miata to current, the FD RX-7 and the RX-8.

Mazda FD RX7 Cracked Power Plant Frame PPFHowever, with increased power or stress from wider and stickier tires, the stock PPF is prone to cracking.  The solution is to remove the PPF and replace them with traditional transmission and differential mounts.

Banzai Racing Transmission Brace FD RX7We sourced the transmission mounts from Banzai Racing, which is laser cut from ¼” steel plate and features Energy Suspension’s patented interlocking 70S durometer urethane mount to control movement of the transmission without adding NVH.

Sikky Manufacturing Mazda RX7 HD Differential BraceThe heavy-duty rear diff brace is from Sikky Manufacturing and supports the front of the diff by connecting and spreading the load across 8 factory bolts in the chassis of the car.  A small, hard durometer front bushing is used to reduce NVH compared to solid-mounting the front of the differential.


  1. Good writeup guys! Is the FD PPF really that heavy? I only have experience with the NA/NB Miata PPF which is a very light aluminum piece. Maybe only 5-10lbs. Is the FD one steel instead?

  2. I’m completely unfamiliar with Mazda’s ppf, so apologies if this is a dumb question. The ppf looks like it provides a bit of longitudinal stiffness that isn’t replaced with the new parts. Is there a risk of increasing the stress at some of the subframe connection points as a result?

    Love the project regardless – thanks.

    1. No worries at all, thanks for the feedback. The purpose of the PPF is to turn the entire drivetrain from the engine to the differential into one solid unit. So the entire drivetrain hangs off of the two engine mounts and the two differential mounts. The new setup changes this to a more traditional layout where the transmission is supported by a (new) bushing and the front of the differential is supported by a (new) bushing. Each additional bushing triangulates the engine/trans and the diff to provide longitudinal support and stiffness.

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