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I've been doing some deep diving into the use of a planetary type gear reduction for use with the Leaf motor. This after market gear reduction supplier has a definite warning about the upper RPM limit of its planetary unit:
Do the Blackbox people have a similar warning? I think the problem is that the small planetary gears turn at such a high RPM, relative to the other components, that problems can come up with the bearings supporting the gears. This makes the bearings the weakest link in the power train. Similar problems show up in helicopter gear boxes with planetary gear drives:
It may not be a problem in your case, with intermittent use. That may not be the case for those of us wanting to use the Leaf motor with a planetary gear reducer for long periods of highway speed, on road use.
The Blackbox does not have those limitations. The Teralow 4:1 transfer case kit is a very bad design and is nothing but problems for everyone that uses them, they've been around for years but hopefully will go the way of the dodo with JK and JL 4:1 transfer cases being so available. JK/JL ones do not have any practical speed limitations as they are OEM parts that are actually designed correctly. The Blackbox uses NP/NV 241 style planetaries, and again as these are actual OEM parts sourced from an OEM transfer case, there is no speed limitations on them. I use one (technically it's an Ecobox because I'm cheap, but it is the same thing) in my Cherokee as the primary reduction and will run up to a 3000-4000 input RPM with it without issues.

I believe the Blackbox reducer that I have uses the planetary from a GM tranny, if not the Powerglide then something similar. I have been through this a couple times in the thread but it will be actively cooled and the truck will not go to the full 10,000 RPM. Starting small and working my way up.

@electro wrks I think I will take your advice and pin one side of the shaft.

I have not done any work on the truck since the first day I got it moving. The vibration is primarily because the motor and t-case are not tied together and move independently. The motor is also twisting sideways. I have some ideas on how to tie the two pieces together with steel and also stop the motor from twisting. That's the first thing I'm going to work on once I get back at it.
The other poster that suggested you attach them together with a torque tube is correct, or at least I think thats the best option. If the motor and gearbox are twisting relative to each other then the ujoint angles will never work to cancel the velocity change they cause. You may be able to get it acceptable by mounting everything so there is considerably less movement, and making sure the angles are all equal and opposite to each other. The other option is to use a double cardan joint on one or both ends, but this will likely cause its own issues due to the length of these joints, however they do not cause the velocity change issues seen in a regular single joint. A CV shaft also might work well, but again the length issues are probably going to make it impractical. The reality is it would be best to just take the angular change out of the equation by joining both ends.

Really interesting build though, so I hope you get it sorted.
 

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The Blackbox uses NP/NV 241 style planetaries, and again as these are actual OEM parts sourced from an OEM transfer case, there is no speed limitations on them. I use one (technically it's an Ecobox because I'm cheap, but it is the same thing) in my Cherokee as the primary reduction and will run up to a 3000-4000 input RPM with it without issues.
The issue is that 3,000 to 4,000 RPM is below the mid-point of the speed range for the electric motor being used; being restricted to that speed in an EV with only the Blackbox and transfer case to shift (no conventional transmission) would limit performance, and that speed is too low for optimal motor efficiency other than at the lowest power level.
 

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The issue is that 3,000 to 4,000 RPM is below the mid-point of the speed range for the electric motor being used; being restricted to that speed in an EV with only the Blackbox and transfer case to shift (no conventional transmission) would limit performance, and that speed is too low for optimal motor efficiency other than at the lowest power level.
It can definitely handle 5000-6000rpm without issues in the short term. I don't know about long term/continuous usage. Guys were using these reduction boxes in U4 and other extremely punishing racing, and they would definitely throw that type of input speed at them over and over, but in off road racing you accept your entire drivetrain is effectively on borrowed time. I would be concerned about oil foaming and heat buildup if you did it continuously, but that would be something to evaluate as needed. Foaming can be combated with different oils (those planetaries are meant to be living in ATF, NWF calls for gear oil because it's a safer option for the shock loading and lower speed environment they envision it living in). If heat management is necessary it is entirely possible to add an external oil pump and cooler to it, and I believe some of the people racing with them were/are doing it, it certainly is a common mod to transfer cases while racing.
 

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It can definitely handle 5000-6000rpm without issues in the short term.
Good, but a unit which is really suitable for a Leaf motor would handle 10,000 RPM short term, and perhaps 7,000 RPM continuously. A Nissan Leaf on a highway runs over 6,000 RPM at moderate highway speed (~100 km/h, ~60 MPH) with its stock gearing. The same power is available all the way down to 3,000 RPM, but gearing for lower speed on the highway means less torque (due to less multiplication of the motor's limited torque) at low speed.
 

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Discussion Starter · #128 ·
Thanks for the info @2drx4, that is good to know. I am well outside the design of the Blackbox but I'm also hopeful that it will work for me. I had a fixed reduction gearbox quoted that would bolt onto my motor and also onto the transfer case and it was over $10k for a single unit so for now this is the solution.

@brian_ my current idea is to use four pieces of angle steel like I used to build my battery box and weld them in between the mounting plate for the motor and BB in an X pattern around my existing driveshaft. It would be like a poor-man's torque-tube.

My gearing is 2.7:1 BB into 4.1:1 diffs with 33" tires. At 6000 RPM, the wheelspeed is 53 MPH. 56 MPH with my planned 35" tires. In double-low range (2.4:1 + 2.7:1) at 6000 RPM the wheelspeed is 23 MPH so I'll probably end up using more RPM while offroading than on the highways. I'll probably also only shift to double-low range for the most challenging of obstacles and drive most of the trails in low-high.
 

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Running a gearbox up to 6500 RPM in offroad competition is very different than running it continuously at 6500 RPM.

As far as "no speed limit", sounds like either a hack in a basement makes them or you didn't get the spec from the person who designed the box.

Stuff always breaks at the most expensive place, or inconvenient time, to load it on a flatbed. Realize most, if not all, tow companies will not tow an electric with any axles rolling. At a competition, you laugh it off and trailer it home. On the shoulder of an Interstate highway, it can get you or the tow driver killed.

Road vehicles need reliability. Your wallet needs it done once, correctly.
 

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Discussion Starter · #130 ·
Running a gearbox up to 6500 RPM in offroad competition is very different than running it continuously at 6500 RPM.

As far as "no speed limit", sounds like either a hack in a basement makes them or you didn't get the spec from the person who designed the box.

Stuff always breaks at the most expensive place, or inconvenient time, to load it on a flatbed. Realize most, if not all, tow companies will not tow an electric with any axles rolling. At a competition, you laugh it off and trailer it home. On the shoulder of an Interstate highway, it can get you or the tow driver killed.

Road vehicles need reliability. Your wallet needs it done once, correctly.
Ok @remy_martian your ignorance is on full display here. I appreciate some of your input, but sometimes you are just so off...

The type racing he is talking about is Ultra4, the highest level of King of the Hammers which is a 165 mile race through the toughest terrain like vertical rock walls and huge mud pits and top speeds of over 100 MPH through the desert that takes places over the course of 14 hours.

My truck defined by its 30Kwh battery will only be able to go 30-40 minutes on the highway before the battery runs out...maybe.

Lastly, my use case is for an off-road trail truck that I will tow to the trailhead on a trailer. I certainly won't be on the interstate highway! :LOL: I am prepared for break-downs, in fact I expect them. I am going to build a tow bar on the front of my Land Cruiser so that it can be retrieved from the middle of nowhere and luckily my tow vehicle is also a Land Cruiser that can also get to the middle of nowhere and back.

 

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In reality, my goal for top speed is 50-55 MPH so that I can go through the town of Moab without getting rear-ended by semis and the like. I think that's totally reasonable and doable.
I think so too. One you sort out the vibration issues you can do some testing. See if it gets too hot. Address the issues if needed. Like you said, you're not doing actual highway trips, and these things have survived some epic abuse at the hands of racers.
 

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An electric seems like an oxymoron during environmental destruction playtime.

Better replace that girly bumper and guard that grille, then, because only it stands between a rock and your battery case going into 4th of July celebrations.
 

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Discussion Starter · #134 ·
An electric seems like an oxymoron during environmental destruction playtime.

Better replace that girly bumper and guard that grille, then, because only it stands between a rock and your battery case going into 4th of July celebrations.
I have enough dom tubing and other steel to build bumpers and sliders. I wrote in this thread I'm building bumpers and sliders and showed my winch. Thanks for joining at the last second.
 

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The gear reduction part of the build does seem difficult for people looking for sustained freeway driving after conversion of a rwd car using the leaf motor. This build is an off road only vehicle so probably a non issue.
For mostly freeway rwd conversion using leaf motor mounted in the front of vehicle, has anyone tried modifying the stock leaf gearbox to be used with rwd prop shaft and diff.
Seems like 2 options (just brainstorming here maybe neither of these would work)
1. Weld up the diff and set a dummy shaft in one cv shaft output, prop shaft to the other. I guess you would need a very special rear differential that is close to 1:1 ratio to maintain ability to go hwy speed.
2. Connect to the first reduction gear set output in the leaf gearbox leaving the diff and cv outputs unused , this would mean modifying / creating a custom gear box case and output from the first reduction gear shaft.
 

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For mostly freeway rwd conversion using leaf motor mounted in the front of vehicle, has anyone tried modifying the stock leaf gearbox to be used with rwd prop shaft and diff.
Seems like 2 options (just brainstorming here maybe neither of these would work)
I don't know if the builder really wants this in his thread, but...
1. Weld up the diff and set a dummy shaft in one cv shaft output, prop shaft to the other. I guess you would need a very special rear differential that is close to 1:1 ratio to maintain ability to go hwy speed.
Yes, that would work (although preferably with a spool rather than welding the diff). Somebody actually proposed essentially the same thing in a Honda forum, and none of the responses could suggest a source. Although a final drive unit without reduction is rare, some of the rear final drives in AWD vehicles are made to work with a shaft that turns at or near from axle speed (instead of the usual transmission output shaft speed), and appear to be near 1:1; Haldex units from VW or Audi applications might be examples. Unfortunately at least the Haldex units also incorporate a computer-controlled clutch on the input which wouldn't be needed or wanted.

I don't think that the "dummy shaft" would be needed, just a cap to keep gear oil in the transaxle.

2. Connect to the first reduction gear set output in the leaf gearbox leaving the diff and cv outputs unused , this would mean modifying / creating a custom gear box case and output from the first reduction gear shaft.
I read about someone doing that, but I don't have a link to it.

Roadstercycle seems to have done essentially the same thing with a Tesla LDU (large drive unit), building a custom case and using only the first-stage reduction gears (which have a 3.19:1 ratio in that case): Tesla LDU drive shaft conversion.
 

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I don't know if the builder really wants this in his thread, but...

Yes, that would work (although preferably with a spool rather than welding the diff). Somebody actually proposed essentially the same thing in a Honda forum, and none of the responses could suggest a source. Although a final drive unit without reduction is rare, some of the rear final drives in AWD vehicles are made to work with a shaft that turns at or near from axle speed (instead of the usual transmission output shaft speed), and appear to be near 1:1; Haldex units from VW or Audi applications might be examples. Unfortunately at least the Haldex units also incorporate a computer-controlled clutch on the input which wouldn't be needed or wanted.

I don't think that the "dummy shaft" would be needed, just a cap to keep gear oil in the transaxle.


I read about someone doing that, but I don't have a link to it.

Roadstercycle seems to have done essentially the same thing with a Tesla LDU (large drive unit), building a custom case and using only the first-stage reduction gears (which have a 3.19:1 ratio in that case): Tesla LDU drive shaft conversion.
Thank you for the detailed response. I will stop derailing this awesome build thread.
The electric land cruiser build is inspiring. Looking forward to the next installment.
 

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1. Weld up the diff and set a dummy shaft in one cv shaft output, prop shaft to the other...
Don't forget that when you lock one of the output shafts, the other spins at 2X RPM.
Welding up the diff means making it into a spool, so both outputs turn with the ring gear. It is not the same thing as locking one of the outputs stationary.
 

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Discussion Starter · #140 ·
Not much new except I charged it up (to 80%). Did it a few hours a day for a few days as I'm still using the 120v Nissan EVSE. Going to do the 240v mod on it soon. Otherwise I ordered all new steel braided brake lines and rear hardware to do a complete brake job. This truck has a LSPV (low-sensing proportioning valve) and I'm going to delete it. It is supposed to adjust the rear brake bias when weight is added to the vehicle but most people find it just makes a spongy brake pedal feel and weak rear brakes when you need them. Since this is basically an experimental vehicle I want the brakes to be as strong and reliable as possible.

 
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