# Motor choices for heavier truck



## WC53 (7 mo ago)

Are there any reasonable motor choices for an old military 4wd truck? About 6300 lbs dry weight, 8300 GVW. It would be nice to have highway speed for short durations.

I have been reading many threads but most seem to be geared towards lighter vehicles. Thanks


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## remy_martian (Feb 4, 2019)

Your issue is battery, not motor. 

What range are you expecting and will it be loaded/towing?


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## WC53 (7 mo ago)

Towing will be limited and if slow, low speeds, say 3500lbs. Two adults and some gear probably sitting about 7K most of the time. Range, 200 fantastic, 150, ok. Rather have unneeded reserve. Adapting the three speed manual is possible if gearing is needed based on motor choices. Trying to decide which way to go with project. Working on it with a youngin who will get the truck in a few years (he’s 35 now). EV vs turbo six, lol… something different than working on golf carts.

And yes, batteries, batteries, batteries


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## remy_martian (Feb 4, 2019)

Model X GVWR is 6768#, but it's not an aerodynamic brick and is not dragging paddles (diff ring gears) through 90W fish oil. It'll tow 5000#.

I'd *guess* you'd about double the amount of battery you'd need over an X, maybe 50% more....your range needs are pretty high.


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## CliffordK (Oct 8, 2011)

It would seem to me that one might try to attach one drive motor to the front differential, and one drive motor to the rear differential. No differential or timing between the two needed.


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## remy_martian (Feb 4, 2019)

No torque or timing management needed between the two motors...really?
🤦‍♂️


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## piotrsko (Dec 9, 2007)

remy_martian said:


> No torque or timing management needed between the two motors...really?
> 🤦‍♂️


Sure if you dont care about operation, cooking a motor, or burning out the controller it would work for a while until the motors became un synched.


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## WC53 (7 mo ago)

Of course range expectations are subject to reality. Aerodynamics are really bad, but hey top speed was probably designed as 45 backin 43’. The vehicle, I admit, is a play thing. After a few decades of bouncing around the farm, the motor and trans need redone. The vehicle will go to a relative in a few years as I time out. He brought up the possibility of EV and we are both researching the feasibility. I admit to being interested. We have worked on a couple of 72v golf cart projects which were fun. I don’t think this project will be “fun” as the computer aspects will be steep for me if we go converting OEM usedparts.

Reading all the different threads, GS450H too light? And only if the L110F tail section is adaptable. Although current transfer case is divorced. UQM PP160 at a much greater cost.
Not remotely looking at going to independent suspensions via the transaxle motors out there.
Just as an fyi, gear ratio is presently 4.89 with 38” tires. We plan on reducing tire size.

Thanks for the thoughtful replies.


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## piotrsko (Dec 9, 2007)

Myself, I would leave the powertrain intact and just use one big tesla motor which makes more Hp/torque than your factory motor. Less planning, fabricating, controls, and you only need one set of everything. Btw a friend's '26 ford is 65mph freeway capable.

However it's your project, and YMMV


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## WC53 (7 mo ago)

That is certainly the way I am leaning. Trying to learn the differences in motors and corresponding controllers and which systems present additional headaches with integration and leaving room for battery packs


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## remy_martian (Feb 4, 2019)

A Leaf motor is fairly cheap and will get you around 70HP as a direct drive, which is plenty. Arguable in direct drive you would get away with using a 200VDC pack.

With a WC53, you have a LOT of room in the back for battery, even if it's on the cabin floor. You are not constrained to "under the hood" to keep the weather off the pack like many vehicles, and being "in the cab" means you might get away with using a dirt-cheap air cooled LEAF pack because it's happy when you're happy temperaturewise.


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## WC53 (7 mo ago)

Thanks,
Looking at putting as many batteries under the floor as possible to keep the already high CG down. 
I will look at some leaf options. I did a leaf golf cart battery conversion some years back. Just assumed the motor would be vastly underpowered.
There is a unit from an LX600h a few hours from me, but seller doesn’t have any peripherals.


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## brian_ (Feb 7, 2017)

CliffordK said:


> It would seem to me that one might try to attach one drive motor to the front differential, and one drive motor to the rear differential. No differential or timing between the two needed.


Yes, that works, and it is what every production AWD EV does; note that an old part-time 4WD truck is not a production EV. Of course this requires a controller/inverter per motor. You would need to coordinate the torque applied at each axle appropriately, and speed (wheelspin) limit each one.

There is, of course, no reason to synchronize the two motors, and that's not even possible while turning (since the front wheels must turn faster than the rears in a corner).


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## remy_martian (Feb 4, 2019)

Every older 4WD on the planet locks the front and rear diffs together...so, not exactly, Brian


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## brian_ (Feb 7, 2017)

Note that an old part-time 4WD truck is not a production EV; no production EV drives both axles with one motor. The crude part-time 4WD systems in these old-style vehicles (which are still available) synchronize the axle speeds with a shaft, requiring tires to slip for the vehicle to turn; that's not feasible with separate motors, nor is it desirable in any case.

All of the features of a 4WD/AWD system used with an engine exist to get drive to all of the wheels from a single source (with, obviously, a single speed), and none of that is required with the separate motors that are practical with electric motors, but not with internal combustion engines. The differential at each axle which is used with a one-motor-per-axle configuration (the most common in production AWD EVs) is the remaining feature of this type (allowing different left and right wheel speeds from one motor), and even it is eliminated with one-motor-per-wheel, which is done at the rear of (for instance) the Tesla Model S Plaid and at both ends of the Rivian R1T/R1S.


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## remy_martian (Feb 4, 2019)

"(the front wheels must turn faster than the rears in a corner)."

Don't think so. Outers faster than inners, but that's the respective diff's job. 

4 wheel high is a locked front and rear driveshaft on a 4WD which is why you aren't supposed to run it on dry pavement. AWD has slip.


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## Ken S (8 mo ago)

In addition to the outside wheels tracking a wider circle than the inner, the front wheels track a wider circle than the rear, unless the rear wheels also steer (like on a skateboard). So yes, either there needs to be a differential between the front and rear (as in full-time AWD), or something must slip (mud, dirt, snow, etc...)


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## WC53 (7 mo ago)

Detroit


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## WC53 (7 mo ago)

So, hmmmmm, help, lol
If possible would like to bolt up to manual tranny and go from there, but maybe not possible. Tesla unit possible only using first stage gear reduction puts me in the rand of 3:1? Right in the range I would need. Of course Tesla cost and complexity.

GS450h or LS600h hybrid. It is the in the range of high gear of 1.9:1? Workable. Not sure if the low selection is still available with locked input shaft to combine MG1,MG2. Sustainable times at power?

Nissan Leaf: lots more out there and parts, but 8:1 ratio not really workable. Am I missing a flashing sign with the leaf and calculating wrong?

My old brain has been reading everything I can find on the differences and look towards a best option. Clearly I am looking more for lower speed and throttle smoothness than doing donuts.

Thanks!


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## remy_martian (Feb 4, 2019)

You missed Torquebox + motor of choice

You also should take a close look at what @D&VsEVJeep is doing in their thread...one of the more elegant ways to do it, imo.


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## piotrsko (Dec 9, 2007)

Want torque but 8:1 is too low on a motor that will spin insanely fast? As in 65 + vehicle speed? What am I missing here? Your vehicle has bigger than 31" diameter tires.


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## WC53 (7 mo ago)

I saw torque box and its price, lol, was looking at used OEM options first. D&V’s thread and videos are very well done and probably they way that makes the most sense time and direct application wise.


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## WC53 (7 mo ago)

piotrsko said:


> Want torque but 8:1 is too low on a motor that will spin insanely fast? As in 65 + vehicle speed? What am I missing here? Your vehicle has bigger than 31" diameter tires.


Maybe my math was off. When looking at that 8:1 plus my 4:89 rear end. Was using a calculator for transfer case and crawl ratios. Was getting 30mph at 9000 rpm.






Final Gear Ratio, Crawl Ratio, Tire Size Calculators


The last year model suburban available with a manual transmission.




4lo.com


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## brian_ (Feb 7, 2017)

Ken S said:


> In addition to the outside wheels tracking a wider circle than the inner, the front wheels track a wider circle than the rear, unless the rear wheels also steer (like on a skateboard). So yes, either there needs to be a differential between the front and rear (as in full-time AWD), or something must slip (mud, dirt, snow, etc...)


Correct 

For other members whose expertise lies in electronics rather than mechanics, and so don't understand this, here's an illustration:








This is captioned "When a car turns, each wheel has to travel a different distance to make the turn", and from an article about 4WD systems.

Here's a version from an article on steering geometry, showing the different radii of the circles that each tire follows, all the way to their common centre:









There are many other illustrations online, but it's easy enough to do the geometry or just run a tape measure from the centre of the turn (in line with the rear axle) to the different distances (and this different rotational speeds) of the four tires.

All four radii are different, but the average of the fronts (the speed of a front axle motor, or input to a front axle differential) is greater than the average of the rears (the speed of a rear axle motor, or input to a rear axle differential).


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## brian_ (Feb 7, 2017)

WC53 said:


> When looking at that 8:1 plus my 4:89 rear end. Was using a calculator for transfer case and crawl ratios. Was getting 30mph at 9000 rpm.


Right... 8:1 is a reasonable overall motor to wheel speed ratio for an EV motor, car-sized tires, and highway use. 39.12:1 (the product of an 8:1 gearbox and a 4.89:1 final drive, even without a transfer case reduction in addition) is way too short (to much reduction) for road use with any reasonable tire.


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## WC53 (7 mo ago)

brian_ said:


> Right... 8:1 is a reasonable overall motor to wheel speed ratio for an EV motor, car-sized tires, and highway use. 39.12:1 (the product of an 8:1 gearbox and a 4.89:1 final drive, even without a transfer case reduction in addition) is way too short (to much reduction) for road use with any reasonable tire.


Thanks, I thought I had it correct. Just as any FYI, for that calculator, I used the transfer case entry for the various OEM EV gear reductions and then varied the motor rpm based on the individual motors efficiency peaks to see where they would fall.


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## remy_martian (Feb 4, 2019)

You are designing for torque, not efficiency for a truck.


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## piotrsko (Dec 9, 2007)

By any chance did you consider typical output shaft rpm of the motor and that associated torque in lb/ft? Back to the 8:1, running at 2,000 rpm shaft output is probably faster than what you want, but would be good for twice your estimated 30 mph. Even in a vertical climb, anything more than a percentage over the weight of the vehicle in lb/ft would be unnecessary assuming in vertical you can get the traction. If you can get traction, I can get you a pot of dollars and lots of fancy trophies

Not pushing the leaf motor, but demonstrates the trade offs.


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## WC53 (7 mo ago)

piotrsko said:


> By any chance did you consider typical output shaft rpm of the motor and that associated torque in lb/ft? Back to the 8:1, running at 2,000 rpm shaft output is probably faster than what you want, but would be good for twice your estimated 30 mph. Even in a vertical climb, anything more than a percentage over the weight of the vehicle in lb/ft would be unnecessary assuming in vertical you can get the traction. If you can get traction, I can get you a pot of dollars and lots of fancy trophies
> 
> Not pushing the leaf motor, but demonstrates the trade offs.


I just don’t see the math.

Running 16K rpm maxed out gives 46 mph with a 1:1 transmission,
If I found a transmission with a .67 overdrive it would go 69 which is certainly fast enough, but that again is at the motor turning 16k.
Allegedly they are going to produce 4.30:1 gears this year. If they do, that give 65 at 13k with OD trans.

If you are suggesting using the entire transaxle, I am not interested in that option. Now if there was a different output gear set for the leaf motor, then it changes the dynamic. I know a 4:1 has been discussed, but that is all I found.

I could be having a senior moment here if you are saying something I am not seeing. It has been a decade since I have done motor and gearbox swaps. Edited to add I just saw two builds, @ElectricLandCruiser and @Rockcrawler who did this.


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## UglyCarFan (8 mo ago)

So, what is the conclusion to this interesting post? Is a Leaf motor enough to meet his objective? A Tesla? A couple Siemens? How big a battery?

Last week I met a very interesting guy who builds custom military rigs, mainly deuce and a halfs. I was lucky enough to go out to his place and look at about 75 units. Really loved the firetruck!

I'm looking to buy a heavy duty trailer, not build an electric big vehicle. But it is interesting to think about peoples ideas for trucks, busses etc.


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