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How do I do an electric vehicle conversion without using the transmission?

I would like to convert my 99 Toyota Tacoma 2wd to battery electric.

Every conversion kit that I’ve come across involves bolting an electric motor to the existing transmission. I would like to remove the transmission and mount the electric motor directly to the drive train.

I’ve heard this can be done successfully but there is little information available. Anyone have any experience or ideas on this?

Asked by:Alex K


  1. Bertsta says:

    I think gearboxes are often used to allow a greater speed range. Single speed vehicles aren’t quick enough for the road (eg. fork lift truck). To keep up a good speed you will have to flog it and the range will suffer as a result.

    But there’s no technical reason why you need a ‘box. Maybe have a look at a fork lift truck and see how it’s done, and maybe “borrow” the parts you need while you’re there ;)

  2. c2builder says:

    This “party line” on this is discussed somewhat in a Bob Brant’s books on electric vehicles. The original book was put out in 1993 and more recently he and Seth Leitman teamed up to rewrite it. The relevant sections, on gears and torque curves, are basically the same in the two editions.

    To summarize, if you’re expecting freeway speeds at the top end, you’re exceeding the range of any type of motor. If geared for high speed, acceleration at the low end will draw a lot of current (I’m repeating this from a possibly poor memory). One small section of these books mentions a transmission-less design which has both an AC and a DC motor. The DC motor is used at low end and the AC at the higher speeds.

    Against all of that, however, I’m pretty sure that AC Propulsion’s designs (San Dimas, CA), Aptera’s (Carlsbad) etc don’t use transmissions. My advice would be to contact controller manufacturers (Zilla in Oregon, Curtis (?)). Metric Mind, also in Oregon, might be able to help; they deal in high priced, European AC controllers. A section of their website chronicles the conversion of a “money-is-no-object” design.

  3. Nata T says:

    get you bank account open. You’ll need an exoctic electric motor like being built for the $100,000 Tesla. It’ll run from 0 to 14,000 rpm. What have you set up to replace all the other things like power assisted brakes. Power steering. The heater, the AC,

  4. richard b says:

    actually the transmission is there to provide a reverse gear. there is a company in california that does electric car conversions, and they just use high gear and reverse. everything else is removed. an electric motor spind fast enough to allow a rear drive ratio of 3:1 and a top speed of better than 100mph, and the electric motor puts out 100% torque at all rpms, so extra gears as you know are not needed.

  5. Wolf Harper says:

    I like your thinking — I agree getting rid of the ****** is a win.

    However, the folks on the EV List have discussed this at great length, and from their experience I can tell you there are several ways to go about that, and all have compromises. The problem is, most single DC motors don’t have the torque spread to both freeway cruise at 60 mph and also mountain-goat up really steep hills. You also need to figure out how to apply power in reverse.

    #1 AC drive. This makes for a very complicated and expensive controller but a somewhat cheaper motor. AC can do *everything* – mountain goat, freeway cruise, reverse, regenerative brake. To buy a commercial motor/controller package you’re looking at $8000 and up. Ouch.

    #2. forget about freeway. Use a low final drive gearing that will climb you up the hills, and just don’t go faster than 45/50/whatever.

    #3. forget about hills. Use a tall final drive gearing that leaves you unable to mountain-goat.

    #4. Oversize the DC motor. Put a 9″ in a car you’d normally use a 7″ motor in, or an 11″ where you’d use a 9″.

    #5. TWO series-wound DC motors and switch them from ‘series’ to ‘parallel’. Almost every railroad vehicle does it this way. Series for climbing hills, parallel for freeway. An alternative to “parallel” is “single motor”, i.e. short around one motor, simpler switching but less power available.

    #6 Separately Excited DC motor. The controller is somewhat more complicated and the motors are much harder to come by, you might have to take a series DC motor and pay a motor shop to rewind the fields for SepEx.

    We still need to discuss “reverse”. Without a transmission, you’ll need to electrically reverse the DC motor. That is, reverse polarity of either the field or armature. For that, you’ll need some physical switches. It’s the same kind of switches you’ll need to select series/parallel. It might be possible to implement all that, together, in a big drum switch of some kind, similar to a streetcar “K” controller.

    All of this is going to require some engineering, especially to get the final-drive ratio right. That’s one reason so many conversions use transmissions, makes everything simpler as you can just correct for gearing deficiencies by changing gears. That would be one hedge, keep the ****** temporarily until you figure out how to have the vehicle do everything you want in 4th (direct) gear, then dump the ******.

  6. barntech51 says:

    talk to the folks who do conversions. they know what cooks. I built my conversion without a ****** and it works fine. I have a 5 to 1 reduction. take a cruise thru the sites provided.

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