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I am planning a truck with a Daihatsu D1100 turbo engine. With the engine behind the driver, I think doing the wiring for the automatic will be less of a nightmare than designing the shift linkage for a T50. Also, the ratios work out much better. Since the computer shift points would be way off with the diesel engine, is it possible to use the auto trans by always shifting with the buttons, paddles or the lever?

Hi Wanderingsoul,

Regarding your most recent post (which I'm not approving, though I AM approving THIS one, with reservations), us mods are volunteers and don't necessarily jump on new posts in the first 48 hours. We also get a huge amount of crap, from people who are just trying to get settled in so they can send us opportunities to invest in cryptocurrency, or meet Russian women, or both simultaneously.

We're a Locost group, homebuilt sports cars, and most of us don't know a whole lot about about homebuilt trucks. But we can probably be intrigued if you'll offer us some details

On google, I couldn't find any reference to the Daihatsu D1100 engine, turbo or otherwise, so it's unlikely we'd have much useful to offer you...but we'll give it a try. Could you tell us more about that engine? Like what vehicles it comes from, why you chose the Miata trans for it, and such? Why a mid-engine truck with a front engine transmission? Why a Daihatsu D1100 turbo engine (whatever that is)?

Have you tried Daihatsu user's groups? How about Miata user's groups? I don't know of a single Locost built with an automatic Miata trans, but there are Miata specialist users groups aplenty, and some of them might have useful information for you. How did you find that that trans would fit your engine? I suspect there are better sites to explore shifting Miata automatic transmission manually only, but maybe they've not been helpful.

You can't include photos until you've been on for a while, but you can tell us more to whet our curiosity.

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Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles

I don't know what I was thinking. Apparently, I wasn't. I meant the Kubota D1100 turbo. I didn't know what normal response time was. I'm not in a hurry, since I'm just in the plotting stages right now.

The primary consideration must be how you want the vehicle to drive. Even if you are manually selecting the gears of an automatic transmission, the driving experience will be worlds apart from a manual transmission. The torque converter, especially when it's unlocked, creates a mushy marshmallow between the engine and the drive wheels. For a truck that's hauling or towing, this is a great thing. For a lightweight vehicle where responsiveness is prioritized, this is a huge downside.

Any Miata transmission will have two main control components - the mechanical valve body and hydraulic passageways, and the electronic controller that triggers the various solenoids in the valve body. At the very minimum, you will need a standalone transmission controller that will allow you to set your own shift points and/or select your own gears based on a paddle input. Expect to spend a MINIMUM of $600 on the controller, if one even exists that supports the Miata transmission. You'll likely also have to dig into the factory valve body and adjust springs, check balls, and passageways to get your desired behavior. Who knows if the factory torque converter will like your engine/vehicle setup at all - torque curve, vehicle weight, and gearing can all have a significant effect on the torque converter behavior. Automatic transmissions are still a bit of a black art and nothing is easy/plug-and-play.

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Ford 5.0 into an M3
mikaelvroom.com | @MikaelVroom

If that's the case, then boy did you luck out coming here! I build and drive a car with that very engine! I heartily recommend the Toyota T50 transmission, because A) it's a whole ot lighter, and with 32 horsepower you're going to want light weight, and B) the R&D for that particular conversion is already done. There's an automatic trans version of that, but it lacks the 5th gear overdrive of the T50 and you're going to want that too.

A truck, huh? An interesting concept. Tell us more.

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Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles

The general idea is a vehicle that looks like a Steyr Puch Haflinger with the width and wheelbase of a Suzuki Samurai, although I may need to extend the wheelbase to allow the drive train to fit. Four wheel independent suspension from VW Jetta front struts, mated to Nissan D22 pickup front differentials. The T50 ratios are acceptable for the speeds I need, but not as good as the ratios of the Miata auto. Also, with the T50 shift lever at least 3 feet behind the driver, making the shifter linkage will be complicated. With the T50 adapter already designed and available, that is the simplest way to go, but autos work much better off road.
I have the original Locost build book, which led me here and to kineticvehicles. That's why I picked the Kubota engine.