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Project Thunderbolt LS3 V8 Miata (Part 4): Rear End, Engine Prep—and the Transmission Arrives


We welded thick steel braces in the firewall area we modified to give our LS3 plenty of living space.

On the left is the stock Miata differential and subframe mount. On the right is our new Getrag Cadillac CTS-V differential and the parts needed to mount it in the subframe.

Steel tabs are welded to the Miata’s subframe to properly locate the differential’s front mounting point.

The differential in its cozy new home. This subframe looks new again thanks to Summit Racing’s Chassis Paint (SUM-SP1402).

The Tremec T-56 Magnum six speed manual transmission will be a perfect match for our 525 horsepower engine.

A low profile oil pan is required for many LS engine swaps and our Miata is no different. This Moroso unit provides plenty of steering rack and ground clearance. Kind of a shame no one will ever see it!

The factory windage tray needed a little modifying to fit in the new oil pan. After installing a new gasket and applying sealer in the proper places, the new oil pan was torqued to factory specs.

The rowdy Chevrolet Performance LS376/525 is one step closer to its home in the Mazdaspeed Miata!

Let’s jump right in and see what’s happening in this episode of our Miata makeover:

  • We welded thick reinforcement braces in the engine bay. These braces are designed to add strength and support back to the firewall area we modified to fit our LS3.
  • We mounted a 3.42-geared Getrag Cadillac CTS-V differential in the stock Mazda rear subframe. This required a bolt-on adapter and a couple of weld-on mounting tabs for the front differential mount. Once the welds cooled, we sprayed the modified subframe with Summit Racing’s Chassis Paint, which we’ve used many times over the years with excellent results.
  • We installed a couple sensors to ensure our Miata’s factory gauges will work properly, and bolted on a new, low-profile Moroso aluminum oil pan.
  • And happy day, our Tremec T-56 Magnum six speed manual transmission arrived!

Watch the Part 4 video here—and stay tuned for Part 5 coming up later this month.


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