Electric 4WD on SUV DIY conversion?

[stillsearching]

I know this has been mentioned in the past on and off here but maybe someone could bring me up to speed because i'm not sure whether any projects ever got further than the brainstorming stage.

(and yes i'm bad for that too, lots of projects I tried to start two years back which have just ended up postponed due to things like work and school and friends who promised help not falling through, but that's how it always is, right? :P)

I'm wanting to more seriously look at the possibility for an electric FWD motor conversion on a large SUV and was wondering how close we are to having an off the shelf solution for that.


Basically to bring anyone up to speed on things i've already decided:
- Planning to use a 3/4 ton Chevy Suburban, either the older 73-90ish chassis or the newer 91-99ish update (the first downsize ever, first attempt at aero, etc. The later ones both are getting larger again and seem LESS aerodynamic plus cost too much for this to start), I expect to use a Cummins 6bt P-pump turbodiesel, NV4500 manual transmission, with an expected max tow of 9990lbs. I would like to use 3.07 or at worst 3.42 axle ratios on normal highway towing tires if that's not too numerically low for startability with that tow weight on a 7% grade but the NV4500 has a steep granny gear helping things. 95% of tows would not be Rockies anyway let alone that weight usually through there. But some future tows WOULD go through there perhaps at max weight to pay the difference of the extra capability just not enough to design the whole vehicle to routinely do it.
- Yes this has to be a Suburban, not a little economy car, because of basic physics of both peoplemoving and towing. I hope to drive a small Jetta with a trailer whenever possible for efficiency, but this is for when I can't and adding a humans-only minivan for when i'm moving 7 people/traveling doesn't justify a third vehicle after carefully analyzing how often it'd be used vs further mpg savings. FWIW improving 2mpg on an SUV is worth alot more than improving 2mpg on an econobox and human-only travel will be much less common than towing (but would be a full load when it happens).
- Because of towing realities this needs to be a RWD-normal vehicle with FWD-electric assist added, rather than an FWD conversion (which i'm aware is more efficient) with RWD added. This needs to be a reliable tow vehicle first that will always get me there and out of there/muddy fields for farm and ranch duty, rather than a max-mpg peoplemover. The biggest MPG savings will be taking the Jetta whenever possible which I will do!
- Yes I hope to fully aeromod this (both vehicle and trailer and coupling them) but i'm exploring whether it's worth it to then reduce mechanical inefficiencies vs the simplicity of just getting part time 4wd. I'm looking for an honest discussion of what specific motors, bolted where, what batteries or controllers would cost, etc - like if you wanted to do this this year how would YOU do it? Secondhand salvage ideas and unorthodox thinking to drop the ticket price is the whole reason for posting this!
- Simplicity wins over best. Less of my pie-in-the-sky dreaming (me wishing for 7 speed medium duty transmissions with the extra fab hassle or uncommon but more efficient engine swap options) and more off-the-shelf get'r-done because otherwise the best solution will never get built. Possible upgrades in the future to stuff like that but not now - I would like something on the road within 2 years from now and need to know how i'd do electric-fwd conversion if I later choose to.


I've no idea whether the best solution is to start with a 2wd chassis or a 4wd chassis - but i'm guessing my main options are either stick an electric motor to the front differential sorta replacing the transfer case, eliminate the differential and stick motors in place of the CV joints (in a 4wd suspension) or stick motors right IN the hub (with either 2wd or 4wd suspension) and i'm open to any of the three (or other) options - plead your case!

I am still up in the air about under what all conditions I need 4wd. There may well be some inexpensively put together system that would provide grip and mobility up to 8mph that would cost a fraction of what one would up to 55mph I mean. This has to be able to drive into a muddy rancher's field 400 miles from civilization and not need a tow every week doing so so the 4WD is nonnegotiable, but it's primarily about not getting stuck or getting unstuck at low speeds until back on the highway. I might not even need truly variable throttle in the controller for that/might just be a couple 'steps' to keep wheels moving.

That said if it's not a huge price difference something that could add stability at highway speeds would be nice sorta like AWD does - this will be a peoplemover at times with kids and that's a safety enhancement if I could turn on the front drive the moment wheel slip was detected for instance. For that matter something that would actually add power would be nice too. I'd considered leaving the cummins around 160-200hp and seeing whether the electric motors could provide the power boost since it seems diesel jetting is most efficient if sized for constant instead of peak load. If the machining/adapting cost and rest of the system costs more than going from 5hp to 50hp per side I just might go bigger. It might be less of a difference than power boosting the engine I mean to get to the same place if some common powerful usable motor is out there.

Experimenting with DIY hybrid ability is not out of the question either - actually it's part of the reason for considering this combo. I just wouldn't expect to experiment with that until later but with strong front motors i'd be mechanically ready just needing programming to make it work. If i'm considering an on-demand AWD 'stability control' adding hybrid is just some extra computer code and this WAS meant to be a bit of a testbed.


Can someone guesstimate how many thousands of dollars would be required to do this, including if using secondhand parts or unusual design (like a 5hp 8mph only "get unstuck" system with stepped/not totally variable throttle for a simplified power controller, and maybe even have to unlock the hubs once i'm on the road again because of how steeply it's geared) to drop the cost? I don't know my exact budget but it's something that if closer to $2000 becomes totally worth trying and as it creeps north of $5000 has rapidly decreasing interest. Some of it is for experimental/I doubt it would pay for itself in mpg savings, but there's a limit how much extra i'll pay to run those experiments I mean.

[cRiPpLe_rOoStEr]

Originally Posted by stillsearching

I'm wanting to more seriously look at the possibility for an electric FWD motor conversion on a large SUV and was wondering how close we are to having an off the shelf solution for that.

When I read "electric FWD motor conversion on a large SUV" the first thing that came across my mind was the Chevrolet S-10 EV, fitted with the same driveline of the Saturn EV1.

Because of towing realities this needs to be a RWD-normal vehicle with FWD-electric assist added, rather than an FWD conversion (which i'm aware is more efficient) with RWD added. This needs to be a reliable tow vehicle first that will always get me there and out of there/muddy fields for farm and ranch duty, rather than a max-mpg peoplemover.

FWD is not really that bad for towing, and that would also leave more space for battery packs. On the other hand, finding a space-saving FWD transmission suitable for your project goals doesn't seem so easy.

Yes I hope to fully aeromod this (both vehicle and trailer and coupling them) but i'm exploring whether it's worth it to then reduce mechanical inefficiencies vs the simplicity of just getting part time 4wd.

Gotta love the good old body-on-frame layout, flexible enough for you to upgrade it easily, or even replacing the entire body with a custom aerodynamically-enhanced one made out of some lighter material (fiberglass, aluminium, whatever you'd want) if you feel like.

I've no idea whether the best solution is to start with a 2wd chassis or a 4wd chassis - but i'm guessing my main options are either stick an electric motor to the front differential sorta replacing the transfer case, eliminate the differential and stick motors in place of the CV joints (in a 4wd suspension) or stick motors right IN the hub (with either 2wd or 4wd suspension) and i'm open to any of the three (or other) options - plead your case!

I'd probably rather start with a 4WD chassis for clearance issues, and also to eventually repurpose the stock transfer case mounts and front driveshaft for the auxiliary electric drive. Anyway, I would still not disconsider to build a custom chassis from scratch if I were venturing in a similar project...

[Daox]

I'll be honest, I didn't read the whole post, mostly skimmed it. I'm not really interested in an electric SUV, let alone a gigantic one (no offense). However, if you're looking for more info on a conversion, Jack Rickard of EV TV did an Escalade conversion.

EV TV

[elhigh]

I think it's an interesting idea, a hybrid fullsize SUV with the electric assist on the fronts. If you were to start with a 4wd Sub you'd have all the front-drive hardware in place. Do the necessary mods to isolate the driveline to the rears for conventional RWD operation all the time, and then hook up your electric drive system to the FWD components. I think you could even retain the low range on the transfer case, you just wouldn't have it anywhere but the rear wheels.

Downsides: weight. Electrics don't love weight as you know, and you're looking at one of the heaviest vehicles available on the conventional consumer market. You'll pick up at least 200 pounds, probably a lot more, just switching to the 6bt. We haven't even talked about the additional weight of the batteries or electric motor yet, not to mention necessary suspension upgrades to contend with the added weight. It snowballs pretty badly.

Aero: the Sub is a big box. Even if it had great aero - which it doesn't - it has the surface area of a small garden shed. So even with a good cD you'll still have a lot more cDA than a smaller vehicle. Your electric range will be necessarily short.

Complexity: Since the 6bt was never stock in the Sub, you have an uphill climb just to get started, bolting one of those in. And THEN you would be adding the electric drivetrain. You must really enjoy turning wrenches. A project like this implies almost endlessly deep pockets, too.

Physics: the 6bt is about 38" tall, 5" taller than the 454. You might not be able to stuff it in and have the FWD components too. One or the other. I dunno if there's a different oil sump available that might free up the space, or if you'd like to do something bizarre like fit up the diesel with a dry sump oiling system. I don't know if that's even possible.

Upsides: room. Engine height excepted, there's a fair amount of space under the Sub to install battery racks while still maintaining decent ground clearance. Bear in mind you'd probably have to sneak the electric motor down there somewhere, too. If you're willing to skip the spare tire that may free up some space for batteries. With over 5000 lb. curb weight, you'll want all the wattage you can stuff in.

Familiarity: You won't be the first guy to shove a 6bt into a Sub, so there's some established wisdom you can call on.

You wouldn't be the first guy to build an electric truck either. Mixing the two, well - that's different. You might be blazing your own trail there - and sometimes trail blazers don't make the news except as Missing Persons reports.

My take, for what it's worth as a mere commentator: I say bolt in the diesel if you're bound and determined, and make the tuning and aero mods necessary to wring every mile per gallon you can out of it. Skip the electric drive option as a blue sky scenario, or maybe spend some time building an electric compact truck for running to the co-op in. Builds of that nature are pretty straightforward and, by the look of them, a lot of fun. I just fear that trying to do everything on something like a Sub will be an exercise in frustration.

[oil pan 4]

The only conversion that I know to be 100% off the shelf is chevy S-10 and ford ranger.
Most if not all of these conversions are done on 2wd.
I do not know of any 4x4 conversions.

For some one to do the one motor per wheel, just forget about it.
Honda and Toyota spent a lot of time trying to solve it, then GM couldn't figure it out, they had to buy the technology from Toyota and this was for front wheel drive only.

Save your self a ton of time and don't depend on other peoples charity.

If I understand correctly what you want the fastest cheapest way to make it happen by far is to get a 4x4, tear out the transfer case transmission, run it 2wd and stick a motor on the front diff some how. You would have to run the most insane front diff ratio you can find, 6.xx would work with a lot of motors.

Oh and you can forget about having a old 3/4 ton suburban with 3.0x gears.
A 3/4 ton suburban will likely have a 10.5 inch full float rear end. If you are considering towing anything near 10k you should be using a full float rear.
The most common ratios for this rear is going to be 3.73 and 4.1 ratios. The numerically lowest you will find will be 3.42. The Numerically lowest ever made was 3.21.
A typical gear set for a 10.5 full float is around $400. The no so typical 3.21 ratio can only be found at one place and they are $600.
I just went through this to get a 3.21 gear set for the 10.5'' full float on my 3/4 ton suburban. It has 4.1 gears and that's not going to fly.
I am not even going to bother with 4x4. I could have used it maybe twice from 2006 to 2014 on my half ton suburban. To get more traction I am adding an ARB air locker and building tire chains.

You could try to tow 10k with an 8.5'' semi float 10 bolt rear but that would be a bad idea.
The highest tow rating I could find on a vehicle that I know only came with the 8.5'' 10 bolt is 5000 too 7000lb.

There are only 1 or 2 people on the diesel forum that have put a cummins in that generation of suburban. They only had to modify and fabricate everything.

[cRiPpLe_rOoStEr]

Do you have any other engine option in mind? What about some 4-cyl out of any random Japanese cab-forward truck?

[stillsearching]

Playing catchup to all posts...

FWIW i'm not 100% stuck on electric, it might well be a hydraulic or even pneumatic motor for all I care, i'm just wondering if i'm totally running into uncharted territory here or if anyone else has done some basic groundwork.

Just to be clear i'm not EV-converting a Suburban. I'm EV-assisting a Suburban, on the fronts only. Big difference. Like this Nissan E-4WD - Wikipedia, the free encyclopedia but reversed! Just putting an electric motor where the engine is and driving a transfer case is NOT what i'm seeking. RWD on engine power is a proven tow platform. I could 'mild hybrid' assist the engine with a power boost there, but i'm wanting to drive the front wheels instead. Besides for braking regeneration if I did later go true hybrid the electric drive needs to be on the front anyway.


As to why a big monstrous Suburban, I already mentioned this HAS to tow up to 10k, there's no way around it. Someone else here talked me into the right way of thinking - the first question on vehicle selection is CAPABILITY, an S10 will not do the job I need to do safely nor will a Chevy Caprice. I would be better off aeromodding a pickup - and I will, probably quite radically.

Even if I were to EV a Suburban, why not? People like the S10's because of the weight capacity for batteries, the right model of 90's Suburban was rated to have over 3000lbs of payload! (higher than any before or since, higher than any Ford)


So responses to the various questions:
- I'm aware in theory FWD might be able to tow these weights theoretically but no available transaxle keeps the efficiency. If I were going to force it i'd swap the powertrain bits from a GMC FWD Motorhome from the 70's, which were upgraded Eldorado/Toronado bits. (TH475 transmission) Since that is a north/south transmission you already lose the lower drag "advantage" of FWD which only works for transverse applications avoiding the 90 degree power bend on the differential and you're stuck with a 3 speed and a poor ratio spread for 10k.
- Cummins 6bt is practically a bolt in with the right swap kit - others have done it, goes right in with a 2wd in those years and a custom crossmember and I think oil pan, a 91up 4wd requires a 3 inch body lift (90down 4wd doesn't). Simplicity is trumping 'best', so... no more 4cyls, only marginal further improvements in mpg vs NVH issues. 6bt over a Duramax and most 4cyls due to cost. Reserve power issues too - a 6bt is less stressed over 200hp vs a 4bt/4bd/etc. NV4500 is basically a bolt in, also due to cost. Marginal improvements of a 6 or 7spd not worth it. AFTER it pays for itself as it is is when i'd play more.
- Diesel stuff totally separate from the electric 4wd/power-assist project, it's just mentioned to explain what else i'm doing. If this were a ground up hybrid for best mileage a smaller 4cyl diesel and bigger batteries would be the way to go, no question. Probably a 7 speed and a custom chassis too. This is more of a ground up tow vehicle on a more basic budget with experiments in mpg-improvement starting with the diesel and then aeromods. One of the other people here set me straight - Capability comes first in the vehicle stable. AFTER it pays for itself I look at some of the fancier upgrades - including maybe the electric 4wd. But if I want to do that eventually I need to know what I will be doing then!


As to the 3.08 gears, i'm considering sticking something like a Ford Sterling in the back instead of the GM 14 bolt with it's annoying ground-clearance-killing center hump. It's strong enough and the gears can go down that low. That or a Dana 61 if I can find one - they're not common, but they're also not in demand as much as Dana 60's are it seems though 3.42 Dana 60's seem the least desirable. Dana 60's have the lowest mechanical drag of all the axle options and are full floating commonly. If I do do electric 4wd the front and rear axle ratios don't need to match, I might even skip the front axle and gain ground clearance.


THINGS I'VE TOSSED:
- I'd never use a 10 bolt for towing these weights after more research, safety and reliability trump MPG dreamin' from now on.
- I've abandoned plans to use any 2-series axle for towing at this point - too much increase in total driveline stress and added fab/complexity. (like custom '509' Dana/Ford hybrid axles) Can play with more radical things in the future if I save fuel money now though, starting with a 7 speed medium duty trans.
- Non-6bt engines at this time. Total project cost and fab work is simpler to just go with a 6bt because it's out in substantial quantity used and less adapters and mods and stuff to do.


Anyway what I was sorta thinking was either get a single Prius motor (or Insight?) and directly power the front axle, or even two Prius motors (and eliminate the front differential) one powering each halfshaft. What the exact dimensions and cost would be i'm not sure, but unless someone is aware of a hub motor that's either cheaper or competitive it's the best idea I can come up with to start with more common hybrid parts while keeping the CV shafts and conventional brakes.

It's that or try to do the same with hydraulics/pneumatics using an accumulator and such which may well be less costly than the big battery packs and such. Honestly i'm VERY VERY interested in a hydraulic hybrid approach - it's much more suited to my 'burst of acceleration' interest with less care about stored energy quantity. But I know even less about setting that up than I would ideas for an electric version.

If there's no transfer case i'm pretty sure a Prius motor would fit under there to drive the front axle - but if i'm driving the front axle all i've really eliminated is the transfer case mechanical efficiency loss. I HAVE eliminated it during all normal driving and towing (in 2wd mode, as part of the reason a 4wd always gets lower mpg even with hubs disengaged is transfer case drag) at least, and the weight of a Prius motor probably less than those big transfer cases, but i'd really like to eliminate that front axle's weight and drag too which is why I wonder about a pair of motors. Dimensions of the motors matter alot more in that scenario obviously.

Now I don't even know anything about Prius motors offhand, i've never looked at one, pulled them out or anything, I only mention it because they're the most commonly made hybrid on the market for a long time so secondhand versions should be as plentiful as i'm likely to see for something in a 44-67hp motor class. For all I know I might be attempting to hack in an actual Prius transaxle minus the engine which might be unfeasible. Other hybrid motors are fine to use too though. A pair of whatever with say 150hp total power boost would be downright dandy especially with the low rpm torque benefits of motors, letting me use lower hp jetting in the cummins 6bt (using the stock 160-215hp rating) more efficient under normal tow duties while performing like a newer truck and spending the money on the electricals instead of diesel power upgrades. AKA electric power assist should boost MPG at other times. While giving me 4wd on demand still and the mpg savings of a 2wd only truck powertrain.


BATTERY: because I am not starting with a 'true hybrid' and more of an acceleration assist and on-demand 4WD I do not need the storage capacity that hybrids (let alone EV's) need. What I need is something that can dump full power to the motors to get things going faster, maybe 30 seconds of hard acceleration or whatever max time wont overheat the Prius motors. Even ongoing 4wd usage at a higher speed if used should not be excessive - add power to the tire to stabilize during a loss of traction is all.

If the economics of a larger battery pack worked out i'd eventually add one, but first i'd like to see if the rest of it works out.


PS: I guess in a way i'm trying to replicate some of the benefit of the 'hybrid synergy drive' in the prius, ie downsizing the engine instead of having an engine with power for all situations. In my case I need the power to pull 10k uphill for minutes at a time and 160-215hp of a stock early 6bt is enough. The motors add acceleration power with or without load, 4wd traction, allow 2wd drivetrain efficiency and may eventually be the basis of a full hybrid system in the future.

[oil pan 4]

You are not going to want a prius motor. They are AC and specifically designed for the prius application.

The ford sterling axle is almost exactly the same thing as the GM 10.5, swaping one in would be a waste of time and money.

If money is no object, sure swap in a ford superduty axle and figure out a make a prius motor to drive the front axle.

I only see at least 3 huge problems with using a TH400 series transmission.
1 Its got a 2.5:1 first gear and 1.5:1 second gear. This thing is going to be a lazy dog when it comes to trying to do anything with a 3.42 or lower ratio rear.
2 Top gear is 1:1, no over drive.
3 No torque converter lockup. Losing converter lockup in my diesel suburban cost me at least 4mpg.
4 This poor gear ratio and operating RPM range you have selected my not develop enough pressure to keep the clutch packs from slipping in the transmission, so the transmission might wear out well before its time or just constantly over heat.

The TH400 series was built cheaply for strength, not efficiency.

[cRiPpLe_rOoStEr]

Originally Posted by stillsearching

FWIW i'm not 100% stuck on electric, it might well be a hydraulic or even pneumatic motor

The only hybrid-hydraulic trucks I can recall are RWD-only, IIRC Freightliner still makes step-van chassis with this setup, and they use a 6-cyl Cummins but it's backed by an automatic transmission. The closest to what you're thinking about is to replicate in a larger size the setup used by Yamaha in some of their off-road racing motorcycles such as the WR 426 2-Trac which had a hydraulic rotor connected to the gearbox to provide auxiliary front-wheel drive.

[oil pan 4]

Before you waste a bunch of time and money you might want to search "GM 10.5 vs ford sterling".