Manual to auto gearbox for electric conversion

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Richard B
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Joined: Sun Jun 19, 2016 11:08 am

Hi, I'm after a bit of wisdom on replacing a manual gearbox with an auto in an SS80V. The interesting bit is that the car is an electric conversion. Originally an F8B motor according to plate. See details on conversion here if interested. Reason for the swap is that the manual box just sprung a big leak, and with the characteristics of the current electric motor/controller combo, a 2 speed auto might make more sense than trying to fix the current clutchless 4 speed setup where 2nd and 4th gears seem to be the only ones required.

Main question is whether there is an Auto gearbox that would be a relatively straight forward swap in terms of mounting and diff/driveshafts, and also whether the gear selector system would fit OK. Engine mounting probably not an issue, existing plate could potentially fit anyway or be adapted. Any thoughts, ideas, advice greatly appreciated as I would love to get the car back on the road.... eventually!
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Brayden
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You could use a 2 speed auto from a Hatch (SS80V) MightyBoy (SS40T) or Alto (CA72V).
Alternatives would be the auto from a Daewoo Matiz, Suzuki Swift or late model Alto.

Interesting that you're considering a slushbox. The few electric car guys I've spoken to said they soak too much power and require drive while stationary, which reduces range.
F8B EFI turbo - Three pots and a snail.
Richard B
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Joined: Sun Jun 19, 2016 11:08 am

Thanks for the info on which transmission would fit.

Re manual vs auto in EV - You're absolutely right, conventional wisdom is that manual is the way to go for the reasons you suggest. Original conversion was exactly that. Clutch removed, used 3rd and 4th gear, worked fine. Have an AC motor now which seems to have less low end torque (but more power) and need to use 2nd gear. Unfortunately not as easy without a clutch, gearbox is pretty knackered. So first conclusion is probably need a new gearbox. So I'm just going back to square one and thinking through options before making decisions. Could continue with manual but will have to put a clutch into it somehow - no flywheel in an EV.

Auto alternative does have a small band of dedicated EV enthusiasts. Very long thread here. I'm by no means an expert on the workings of any type of transmission but my interpretation of the posts in the thread are that you could keep the torque converter, maintaining a low speed idle when stationary, or remove/adapt TC so there is a direct drive on the auto, possibly using a small aux pump to maintain trans pressure.

Now as mentioned, I have no idea if the suzuki auto trans could be adapted or how it would behave. But knowing that I might be able to fit one means that I can try to find the answer to the previous question.

Keep in mind that an electric conversion is a rather extreme transformation so either way so there is going to be some unconventional engineering going on whether it is manual or auto.

Any further thoughts or advice would appreciated - I need a hackers guide to the suzuki auto!

Cheers
 
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Brayden
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For what you need it sounds like the standard 2 speed auto would be perfect. Very simple design.
Bonus is that the bellhousing is identical to the manual box, making physical installation a little bit easier. You'd just have to adapt the torque converter.
F8B EFI turbo - Three pots and a snail.
Richard B
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Joined: Sun Jun 19, 2016 11:08 am

Thanks Brayden, I downloaded the auto trans manual for SS40T and it seems like the shift, kick down etc is all electronic. Sevcon controller I use has multiple analogue outputs so it is possible that I could map an output to control solenoid and also an aux pump if necessary. Definitely worth some more thinking. If anyone has a spare working 2 speed and shifter etc, I might be interested. 
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Brayden
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I should mention that automatic models (Alto, MB, Hatch) have a different wiring loom to manual models, so if you want the auto to work like it did from the factory you'll need to chase a loom and a bunch of other parts. The box only has one solenoid, which is operated electronically from combination of vacuum sensor, speedo sensor and kickdown switch on the accel pedal. (Running through a control unit). If you don't want to bother wiring all that stuff in you rig it up with a toggle switch (or paddles) and shift between high/low gears manually. You will still need the factory shifter and cable though.
F8B EFI turbo - Three pots and a snail.
BLSTIC
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You *could* go for a converterless auto setup teamed with a manual valve body. It's used in speedway racing occasionally, effectively locks the input shaft and the pump together and bypasses/deletes the torque converter. Still need a minimum RPM to get drive (just enough to start building pressure in the valve body and drive will start) but it's extremely low. It's basically a way to combine the efficiency of a manual with the physical strength of an auto (ever seen an auto with stripped gears?) in a situation where you wouldn't expect to change gears (no those cars don't do standing starts nicely, but then, your engine can start at zero RPM if it has to)
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