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Automotive Rollbars and Aftermarket Products for Miatas and MGBs

Boss Frog 8.8 Differential Swap Kits for 4-Cylinder Engines

Kit #1 – Transmission Support (stock 5-speed)

Kit #2 – Driveshaft

Transmission Support (stock 5-speed) – this kit includes heavy 10ga frame rail channel sections to mount the crossmember to the frame.  The channel sections include mounting plates where the transmission crossmember is bolted.  A urethane pad helps absorb vibration and torque.
The kit includes;

• frame rail channel sections (2)
• transmission crossmember
• urethane pad
• grade 8 hardware and installation instructions

4CYL-K1 - Transmission Support kit

Shipping & Handling $30

If you significantly increase the horsepower of the stock 1.6 or 1.8 Miata engine, the stock drivetrain may not be able to keep up. If fact one of the first casualties is often the Mazda differential, which will fail under high HP applications.

One way to fix this is to swap out the stock differential with a Ford 8.8 Thunderbird differential and IRS axles. This is the same differential mount kit as the V8 swap (LSx-K3a or K3b), and also requires one of the V8 axle kits (LSx-K4a, K4b, or K4c).

When the stock Mazda differential is removed, the PPF (the brace between the transmission and differential) must also be removed. In order to properly align and support the tail of the stock Mazda 5-speed transmission, a new Transmission Support Kit must be used. A new driveline is also required to connect the transmission to the 8.8 differential.

Driveshaft – the Miata u-joints are very small and not made for big horsepower.  We supply larger series u-joints and yokes, to be able to handle much higher horsepower.
The kit includes;

• custom length driveshaft
• front yoke for stock 5-speed transmission
• rear mount for 8.8 differential
• grade 8 mounting hardware

4CYL-K2 - Driveshaft kit

Shipping & Handling $30

lose the tail, grow some legs