[jwetering]

Hi folks. I'm Jasper from North Vancouver BC.

I'm 55 years old and a fairly hardcore gearhead. I'm mostly into German cars and bikes, with soft spot for Toyotas.

I'm pretty sure my next build will be an electric conversion, either a German sedan or station wagon or a Toyota pickup.

So my rookie question is why do conversions seem to all have their transmissions intact while store bought electrics like the Tesla, Bolt, and Leaf seem to go without....

The related question is whether I can build an EV without a gearbox which will give me the usability and (hopefully) the range of a store bought vehicle..

I've got the shop and the tools. I have a decent bag of experience, just need some time and some funds. Retirement isn't that far away.

Thanks.

 

[reiderM]

Hi folks. I'm Jasper from North Vancouver BC.

I'm 55 years old and a fairly hardcore gearhead. I'm mostly into German cars and bikes, with soft spot for Toyotas.

I'm pretty sure my next build will be an electric conversion, either a German sedan or station wagon or a Toyota pickup.

So my rookie question is why do conversions seem to all have their transmissions intact while store bought electrics like the Tesla, Bolt, and Leaf seem to go without....

The related question is whether I can build an EV without a gearbox which will give me the usability and (hopefully) the range of a store bought vehicle..

I've got the shop and the tools. I have a decent bag of experience, just need some time and some funds. Retirement isn't that far away.

Thanks.

It's a lot easier to just keep the transmission.

If you keep the transmission, the only thing you have to make is the mounting plate to connect the motor and transmission. If you ditch the transmission, you will have to fabricate essentially a whole new driveline. This is obviously easy to do at scale for large auto manufacturers.

Transmissions also let you select a gear ratio, which is fun to have and something you will never have in factory EVs.

 

[Duncan]

Hi
I don't have a gearbox in my car - no need for one
If you have a traditional RWD - longitudinal engine and you are using a large enough DC series motor then you can ditch the gearbox and drive directly to the diff
If you are converting a FWD transverse engined car its more difficult as there is not a separate gearbox

If I was to convert another I would use the complete power unit from a modern EV - and drop that in where the engine and gearbox were

 

[reiderM]

Hi
I don't have a gearbox in my car - no need for one
If you have a traditional RWD - longitudinal engine and you are using a large enough DC series motor then you can ditch the gearbox and drive directly to the diff
If you are converting a FWD transverse engined car its more difficult as there is not a separate gearbox

Ah I see. Although it would work fine with just the diff, you're losing out on torque because a diff alone is usually a 3:1 drive ratio, whereas a transmission and diff combined are typically close to a 10:1 ratio in the lower gears.

FWD cars with transverse engines still have a separate engine and transmission though. They just appear to be more integrated since FWD gearboxes are shorter and wider than RWD.

 

[brian_]

All production EVs have gearboxes, but they have only a single ratio... they are "1 speeds". Even Duncan's DIY car has a gearbox: it has the pinion and ring gears of a Subaru final drive unit (differential), providing enough reduction gearing (probably something in the range of 3.7:1 to 4.44:1) for his car and motor combination. Since an electric motor can produce sufficient power over a broad speed range there is not enough benefit to justify a transmission that can shift between ratios, in most cases.

Conversions often keep the vehicle's original transmission because builders find it is easier to mount an electric motor to an existing transmission than to mount a complete motor and transaxle from an EV in the vehicle and make the axle shafts work. Also, older conversions tend to use lower voltages, which limits the performance of the motor at high speed and makes shifting to keep the motor in a narrower speed range beneficial.

 

[brian_]

If you have a traditional RWD - longitudinal engine and you are using a large enough DC series motor then you can ditch the gearbox and drive directly to the diff
If you are converting a FWD transverse engined car its more difficult as there is not a separate gearbox

FWD cars with transverse engines still have a separate engine and transmission though. They just appear to be more integrated since FWD gearboxes are shorter and wider than RWD.

I assume that Duncan meant that the transmission (gearbox) is not separate from the final drive unit (differential with the final stage of reduction gearing), so it is not feasible to leave out the transmission and keep just the final drive unit. Transaxles don't just appear to be more integrated - "transaxle" means transmission plus final drive ("axle") in one unit, whether that is transverse or longitudinal, at the front or at the rear, attached directly to the engine or at the other end of the car.

An electric motor could be used with any transaxle, if you want to keep the transmission gearing. An electric motor could be used with just any separate final drive unit, but the final drive (diff) is normally not readily separated from the rest of the transaxle in any front wheel drive vehicle, or any rear-engine and rear-wheel-drive vehicle. And a final drive by itself, with it's typical single stage of reduction gearing, doesn't typically provide enough reduction for a high-speed motor.

Any just because almost any generally true statement about design has an exception, the final drive of the Turbo Hydramatic 425 (or 325) in an old GM FWD such as a Toronado or Eldorado unbolts from the transmission section. Of course, that's not a transverse configuration, and I'm not really suggesting that anyone use one of those old things anyway...