# Chevy Bolt motor/transmission



## DrGee (Aug 22, 2018)

Does anyone know if it's possible to remove the transmission from a chevy bolt motor unit? It's not bolted on like the Leaf motor arrangement, but is there a way? I raise the question, because I'm thinking of using one in a rear wheel drive conversion, instead of a gs450h unit.


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## remy_martian (Feb 4, 2019)

The gearbox and motor on the Bolt EV are integrated, so no. Weber has a Youtube video where he disassembles the unit.

My question is why would you want to? The Bolt EV makes pretty fair HP and torque. It's also pretty compact if you pull the inverter and crap bolted to it.

No reason you couldn't "overclock" it, if you're thinking the motor is weak (compared to the GS450H, I'd put it in superior territory), as far as the current you dump into it for short bursts, as there should be plenty of safety factor in the little grocery-getter.


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## brian_ (Feb 7, 2017)

I agree - why not use the complete drive unit, mounted at the rear axle, instead of stripping the motor out and having to provide some other reduction gearing?


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## DrGee (Aug 22, 2018)

Thanks Remy... I was concerned about losing speed and gaining unnecessary torque. My understanding is that its essentially a transaxle for the front wheels. If so, the final drive is the transmission (7.05:1). If l connect that directly to the rear differential (another final drive) of a w220 S-class, it'll give it even more torque, but slow it down by a factor of nearly 3 - or won't it?..


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## remy_martian (Feb 4, 2019)

No...you pull the original diff, put the Chevy in, and run halfshafts out to the hubs. Frankly, I'd go with a Tesla drive unit for that car...


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## DrGee (Aug 22, 2018)

For real Remy, so would I! Just a little matter of price.. I see Tesla drive units going for $4000+ compared with the 1k or thereabouts for the Chevy Bolt motor


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## brian_ (Feb 7, 2017)

DrGee said:


> My understanding is that its essentially a transaxle for the front wheels. If so, the final drive is the transmission (7.05:1). If l connect that directly to the rear differential (another final drive) of a w220 S-class, it'll give it even more torque, but slow it down by a factor of nearly 3 - or won't it?..


That's right, the overall gearing (including final drive) of the Bolt unit would be 7.05:1, so there would be too much reduction gearing... which is why you don't do that, and why I suggested this:


brian_ said:


> I agree - why not use the complete drive unit, mounted at the rear axle...


Then remy_martian suggested it again, with additional details in case my version was not understood:


remy_martian said:


> No...you pull the original diff, put the Chevy in, and run halfshafts out to the hubs.


Of course the whole drive unit (motor with transaxle) needs to fit in the rear, where there is normally only a final drive unit.


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## DrGee (Aug 22, 2018)

Sorry guys - I was typing in my reply to one of Remys' when you were both giving me the answers I needed. Much obliged 👍
I think putting the unit in place of the rear differential is a fantastic idea. Just didn't know that it was doable. One additional advantage is that I can discard the prop shaft along with the Mercedes gearbox - nice weight saving there.


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## remy_martian (Feb 4, 2019)

$1000 for a Tesla SDU these days...in case you don't have room. The Bolt is a bit ugly in that it sits vertical


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## brian_ (Feb 7, 2017)

remy_martian said:


> The Bolt is a bit ugly in that it sits vertical


The complete drive unit has the inverter on top, like all of the other EVs adapted from front-wheel-drive designs; most (including the Bolt) have the charger and other components stacked even higher, on top of the inverter. The motor and transaxle are at the bottom - like every drive unit - as low as a Tesla or anything else. Using any of these vertically-stacked units at the rear of a typical vehicle does mean moving the inverter to behind or ahead of the motor and transaxle.


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## DrGee (Aug 22, 2018)

If can find a Tesla drive unit for $1k, that'll be a game changer..


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## remy_martian (Feb 4, 2019)

brian_ said:


> The [Bolt] motor and transaxle are at the bottom - like every drive unit - as low as a Tesla or anything else.


I must be losing something in the Canadian metric conversion of "low" (multiply by 0.6?), lol

Bolt EV:










Tesla:


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## remy_martian (Feb 4, 2019)

DrGee said:


> If can find a Tesla drive unit for $1k, that'll be a game changer..


$1500 right now, though I've seen one for $1k 









Front Axle Electric Drive Unit Motor Inverter 1035050-00-D Tesla Model X S 2015+ | eBay


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If it fits with the same inclination to preserve lubrication scheme...


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## Evbeddy (Jan 5, 2020)

I raise the question, because I'm thinking of using one in a rear wheel drive conversion, instead of a gs450h unit.
[/QUOTE]

Hey DrGee

Just wondering why your thinking of ditching the gs450h gearbox? It seems like a good unit to me.

Thanks
EvBeddy


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## brian_ (Feb 7, 2017)

remy_martian said:


> I must be losing something in the Canadian metric conversion of "low" (multiply by 0.6?), lol
> 
> Bolt EV:
> 
> View attachment 120820


No, the Bolt image shows the unit (just motor and gearbox) rotated 90 degrees on the axle axis. I don't know why it was displayed that way for the PR photos, but it caught me too when I first saw it.


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## remy_martian (Feb 4, 2019)

Yeah...you're right about the orientation. I've only paid attention to the PR photo






(12:31 ..."transaxle [with motor] weighs 170lb")

It's still looks higher from the axle centerline, though


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## remy_martian (Feb 4, 2019)

Evbeddy said:


> Just wondering why your thinking of ditching the gs450h gearbox? It seems like a good unit to me.
> 
> Thanks
> EvBeddy


It's a good unit, but its advantage of not messing around with the drivetrain for "quick and dirty" carries serious issues like weight, reliability, more moving parts, lower efficiency (a lot of stuff sloshing in lubricant and a lot of rotating inertia), keeps the driveshaft, joints and rear end which are lossy and heavy, and displaces a space where you could stuff batteries for better car balance. There's also cost.... that Tesla drive unit costs more or less the same as the trans AND you get the inverter for the money.

The hybrid trans makes a lot of sense if you're converting the hybrid it came in, maybe. But for a car like an S-class, ....?


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## Evbeddy (Jan 5, 2020)

Hi Remy

Thanks for your reply. There all good points, some that I hadnt thought of. I didnt realise tesla sdu's were as cheap as that. 

One benefit of the gs450h in a rwd platform is the easier ability to have a LSD as your keeping the diff. I know you can get a (expensive) quiaffe unit for teslas LDU but theres nothing for the SDU that im aware of. 

Evbeddy


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## remy_martian (Feb 4, 2019)

Doesn't S-class have traction control vs mechanical LSD?


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## Evbeddy (Jan 5, 2020)

remy_martian said:


> Doesn't S-class have traction control vs mechanical LSD?


Sorry quite likely I think your right. I was really talking about my project and reason for possibly using it not DrGees s class. Sorry for the confusion.


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## DrGee (Aug 22, 2018)

I owned a w220 mercedes several years ago in the UK. It was an S280; 2.8l, 204 hp & 199 lbs-ft torque at 3000 rpm. It felt really quick, even though it was a just a 2.8l (maybe I'm easily thrilled..)
If the Chevy Bolt motor puts out 200 hp, with 266 lbs-ft torque from 0 rpm, it should power the old S-class nicely shouldn't it?


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## brian_ (Feb 7, 2017)

remy_martian said:


> It's still looks higher from the axle centerline, though


The Bolt (and Spark EV, and a few others) use a hollow-shaft motor so the motor is coaxial with the axles; as a result, the top of the motor and transaxle assembly is above the axle centreline by the radius of the motor case. The Tesla units (other than the taller Model S front unit) have the motor axis parallel to the axles and at about the same height, so again the top of the motor and transaxle assembly is above the axle centreline by the radius of the motor case... which is about the same between the Teslas and the Bolt.


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## Tremelune (Dec 8, 2009)

Don't worry about torque, worry about what will _fit_. Even the lowly Leaf motor would outrun half of the stock engines to 60mph.

The W220 has an independent rear suspension, so your play is to modify that to accept a motor with an integrated gearbox. Then you either fab the axles stubs together or have custom ones made.

The hard part is cutting the subframe, positioning the motor, and fabricating mounts without destroying the suspension geometry. Depending on the dimensions of the subframe, the difficulty may swing wildly between Tesla, Bolt, and Leaf motors.

I don't think anyone has a controller for the Bolt motor yet, but I haven't checked in a while, and it's only a matter of time. That's something to think about, though.

What's your plan for the OEM computers freaking out about the engine not being there anymore...?


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## DrGee (Aug 22, 2018)

The work involved in fitting the motor in place of the rear differential sounds daunting. Cutting metal & fabrication isn't anything I've done, but I'd go for it if there are instructions out here on this forum. 
Great question about the OEM computers freaking out.. I posed the same question here last year, but got no answer. Of note, Damien has put a gs450h motor in a 2001-2008 BMW 7 series. That model is loaded with integrated electronics which he was somehow able to by-pass or fool into thinking the ICE was still there. The crucial bits I'd need to function would be the ABS brakes & central locking. The speedo, motor temp & current etc are relatively easy to sort out I think.


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## Tremelune (Dec 8, 2009)

The fab is tough for sure, but if you want to keep the rear differential, your options are pretty much the Leaf or a cylinder motor (which will deliver less power for more money). Dual inline motors is an option for more torque. You might be able to mate the output of one side of a Bolt motor to a driveshaft U-joint...but you'd have to weld the other side and put the motor in sideways...just seems a bit weird. I've never seen it done.

I wonder if it would be easier to fuse a Tesla subframe with the Benz subframe...I'm off in the weeds.

I wish more OEM motors had flat faces and detachable gearboxes.


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## DrGee (Aug 22, 2018)

You guys have really got me interested in putting a transaxle in place of the rear differential. It's the best setup I think, if I can wing it. The Bolt and Leaf motors have a pretty "small form factor" compared to my previous preference - the Lexus GS450H. Surely I can put one of them between the independent rear legs of the w220...


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## brian_ (Feb 7, 2017)

Tremelune said:


> ... You might be able to mate the output of one side of a Bolt motor to a driveshaft U-joint...but you'd have to weld the other side and put the motor in sideways...


You can weld the diff solid or (much better) replace it with a spool, but you can't just lock one side stationary because that will spin the diff pinion gears rapidly and they are not intended to do that continuously.

Even with a spool, the remaining problem is that you still have the roughly 7:1 reduction gearing of the Bolt transaxle in addition to the car's original final drive reduction. That means the Bolt motor will hit its maximum speed at a low road speed. This is the same problem as faced by people attempting to use an EV drive unit (typically from a Tesla) to drive both axles of a 4X4.


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## olegil (Jan 7, 2012)

DrGee said:


> You guys have really got me interested in putting a transaxle in place of the rear differential. It's the best setup I think, if I can wing it. The Bolt and Leaf motors have a pretty "small form factor" compared to my previous preference - the Lexus GS450H. Surely I can put one of them between the independent rear legs of the w220...


The best part about a modern Mercedes, diyelectriccar vise, would be that you can drop the subframe, or even buy an extra, and work on that before even dismantling the donor car.
Fairly cheap to buy a used one:








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If dropping your own, fill up the available space with construction foam first, then you see how much space you have, so you know if you'll need to modify the trunk floor.
Controller should fit in the tunnel, as it normally carries both exhaust and drive shaft. Battery pack can be split between petrol tank space and bottom of engine compartment, leaving a large front trunk for you 

Not sure where a W220 spare wheel sits, but my S210 (E-class wagon. Funny how S is wagon and W is sedan for Mercedes) had it in the trunk, behind the left wheel well. Completely hidden. 205x55-R16. Mind well and truly boggled when I found that. That's also a LOT of battery space if you can utilize it.

If Norwegian laws were not so draconian, I would have done this already. But we can pretty much only rebuild cars older than 1972, because anything newer than that has to satisfy a lot of safety requirements which is outside the scope of DIY. Unfortunately this means no cars with rear subframes (I believe both BMW and Mercedes started using subframes in 1972, allthough I'm not 100% sure on the BMW part).


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## olegil (Jan 7, 2012)

W220 is one of those where the spare wheel is under trunk behind diff and fuel tank is above diff just behind the seats, isn't it?
I guess that's the usual sedan buildup from Mercedes, while the wagons have fuel tank under trunk, behind diff and spare wheel inside trunk, hidden in the wall behind wheel well.

Youcanfitsomanybatteriesinthisbadboy.png ;-)


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## DrGee (Aug 22, 2018)

olegil said:


> (Funny how S is wagon and W is sedan for Mercedes)


Love this! 😂😂


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## DrGee (Aug 22, 2018)

olegil said:


> W220 is one of those where the spare wheel is under trunk behind diff and fuel tank is above diff just behind the seats, isn't it?
> I guess that's the usual sedan buildup from Mercedes, while the wagons have fuel tank under trunk, behind diff and spare wheel inside trunk, hidden in the wall behind wheel well.
> 
> Youcanfitsomanybatteriesinthisbadboy.png ;-)


You're quite right about the location of the spare wheel in the W220. Really good insight into utilising the Mercedes rear subframe! Thanks so much for this. I've looked at images of the Tesla SDU in it's own subframe and compared them with images of the w220 subframe. I really think I can do this. Thankfully, there are readily available hacks to control the Tesla SDU.


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## Tremelune (Dec 8, 2009)

olegil said:


> If dropping your own, fill up the available space with construction foam first, then you see how much space you have, so you know if you'll need to modify the trunk floor.


That is a hot tip...I used a ruler, paper, and a ton of measurements...


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## DrGee (Aug 22, 2018)

Tremelune said:


> That is a hot tip...I used a ruler, paper, and a ton of measurements...


Got it!


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