Grannas IRS 9” rear differential conversion kit for FD3S Mazda RX-7

This IRS 9” rear differential kit for the Mazda RX7 (FD3S chassis) retains the use of the factory subframe but adds in a tubular front support to further strengthen and add support for the pinion on the Ford 9” rear end. It features weld on strengthening plates as well as a super solid X-brace, and solid front mount. The kit retains the use of the stock rear subframe mounts. The rear “ear” mounts include solid aluminum bushings. 

This kit is available with either a LSD center section or with a spool. The FORD 9” is known as the ultimate rear end for its strength, wide usage, and unlimited potential of gear ratios and carrier options.

The kit includes The Driveshaft Shop PRO LEVEL axles which include a replacement billet wheel hubs with a HD spline for more strength over the stock hubs. It is recommended that you to replace the wheel bearings at the time of install.

This kit does require fabrication/welding of the front bridge x-pipe along with the strengthening plates. Once the pieces are welded in, the subframe will bolt into the chassis without any issues.

This first kit is being installed into Len Bacon’s rocket ship for proving, and is available for purchase now. I will be doing 10 kits initially and if they sell well I will continue production on these.

TECH:

INSTALLATION INSTRUCTIONS