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Rear subframe conversion ruminations

5109 Views 83 Replies 10 Participants Last post by  Duncan
Cars with live rear axles make for frustrating conversions, mainly because you have to keep a manual transmission up front. Adapter is a grand or two, and the 2:1 TorqueBox is $4k (plus custom driveshaft). If you ditch the axle, you have to reengineer the suspension, which involves much more than cutting and welding.

Enter the rear subframe swap. Many conversions will take a Tesla subframe and stuff it in the rear. The difficulty here is that Teslas are wide, and many of the cars I'd like to convert are narrow. It also makes using different wheels tricky.

Has anyone successfully gotten an electric motor and gearbox into something like a Miata rear subframe? E30? What are some other rear subframes that are narrow with pickup points that a Leaf/Tesla motor could bolt into without moving the suspension pickup points?

What are the implications of changing the rear suspension geometry and travel while keeping the front stock? For a sportscar it would make me nervous, but for a daily driver or cruiser...not so much—just get over these bumps!

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On our Mazda RX-8 rear subframe conversion, we didn't modify the chassis at all, but we did modify the heck out of the subframe. Got an EM61 Leaf motor in there, could probably fit an EM57 with a remote mounted inverter, but on the Tesla side I don't think a SDU would fit between the suspension points.

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On our Mazda RX-8 rear subframe conversion, we didn't modify the chassis at all, but we did modify the heck out of the subframe.
Do you happen to have any before/after shots? I'd love to know what was really involved. Hopefully you didn't have to change the suspension connection points.
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We didn't change any of the suspension geometry / connecting points.

Here's about the closest I have to a before / after shot. We actually kept the original subframe intact and bought a spare to modify. This shot does not show the final motor mounts or the front crossmember we added.

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Here's the (mostly) final product outside of the car:

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I see the prototype had hard mounts for the power unit - and rubber mounts for the final solution
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