What's inside an electric vehicle gearbox? A look inside an EV reduction gearbox. PART 2

In this video I again look inside an electric vehicle gearbox and correct a mistake I made on the first video, which has now been renamed Part 1. These are simple devices and simply reduce the speed of the electric motor down (that's why they're called a "reduction gearbox") and house the differential. This particular reduction gearbox is from a Hyundai Ioniq Electric 28kWh that's done 100,000 miles. All the Kia & Hyundai EVs use a very similar reduction gear. But then so do all electric vehicles.
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Timestamps
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[@richardhaywoodh]

Great update. Really refreshing approach showing we all don't get it 100% first time. Every day should be treated as a school day for everyone.

[@GoGreenAutos]

Half the problem is all my videos are unscripted, adhoc and I'm looking at the camera screen half the time, so with all the multitasking, I'm sometimes not got 100% brain engaged on the topic.

[@richardhaywoodh]

@@GoGreenAutos all your videos are very informative & engaging, keep up the great work

[@GoGreenAutos]

@@richardhaywoodh thanks 🙂

[@daviddavid-ot8bm]

Hello, do you know sizes or parts numbers of ball bearings for the transmission of the Kia E Niro Mobis 36500-0E7100. Mine's becomes noisy.... If you know motor bearings types too that will be great! Thanks in advance.

[@boredKiwi]

Thank you for demonstrating the physical looseness of the internal magnet as I requested. Hopefully one day we'll be able to understand why a significant number of Ioniq, Kona and Niros are developing powertrain noises. Last November 2022, I changed the gear oil on my Kona and glued a strong magnet on the housing directly under the internal magnet's location to see if that would help restrain it. This year's oil change (that I did last week) came out more green than the black, an improvement. I believe it's aluminium contamination that makes oil black when no oxidation is present. Regarding the Nissan differential issues, one challenge with having a gear assembly with shaft speeds ranging between zero (spiders) and 10,000 RPM (pinion) is that lubrication viscosity requirements are based on the high-speed gear mesh, what's called "pitch line velocity" in order to minimise cavitation. The 70W or ATF grades match that requirement but also have a GL-4 level of extreme-pressure additives which should help handle the tooth loading in the near zero-speed spider gearset. Another challenge is that the small diameter and beveled nature of the spider gears makes it difficult to form an adequately-wide involute tooth profile to spread the load evenly. A larger, stronger spider assembly is really the obvious answer for those particular EVs.

[@velipekkavahvanen2134]

I had recently bearings changed on my 2017 Ioniq 28Kw 118tkm. Both motor and reduction gear. Gearbox was fine, motors bearings bad. Bearings were supplied (free) by Schaeffler. They may make repair kit for Kia / Hyundai first gen EVs. It is not the magnet but the EDM (Electric Discharge Milling) caused by motor axle current, that wears bearings out. Why it is sometimes motor bearings and sometimes the reduction gear bearings that start to fail is not clear to me. I also would like to know weather that brass ring on reduction gearbox is some kind of grounding ring. My repair shop said it is not, but I wonder... Pre ~2019 motors (E500, E700) have steel motor bearings (with conductive grease?)and no grounding brush. These will all go bad sooner or later. Not clear what wears them most, hi speeds, frequent use off full power, temperature or what. 2019 carbon brush was installed between motor and reduction gear, don't know if they moved to ceramic motor bearings also. Some off these units have failed also, but as most are still under guarantee, reasons are not known.

[@boredKiwi]

@@velipekkavahvanen2134 To assist the Hyundai owner's community could you provide the engineering documentation that lead to that conclusion?

[@briangriffiths114]

Good advice about not using all that instant EV torque just because you can. Due to my engineering background, I treat all cars (and other machinery) with great respect and always tend to get the best out of them.

[@GoGreenAutos]

Yes, a skill which is lacking nowadays. So many people just keep repeating or forcing something when it doesn't do what they were expecting!

[@AlainODea]

Really fascinating material. Thank you for sharing this. I am always taken in by how durable these EV components are! Hyundai has really outdone themselves here

[@GoGreenAutos]

Thanks. Glad you liked it.

[@bobuk5722]

Useful life lesson, check, don't guess! Very interesting to see inside these units. Helps to understand how these vehicles work. Thank you for the update.

[@Oresti-007]

Hello, and thank you for the explanation video, I have a Hyundai ionic electric premium, SE, 38 kW with 47,000 miles on it and I just got back from the garage Hyundai approved garage which the diagnosed and successfully under warranty replaced the reduction box, but they didn’t give me a detailed feedback on how the problem occurred. The vehicle was sent to the garage because it was deemed not safe to drive by roadside assistance that I called as I was recommended to do by Hyundai. The reason for calling in the first place was over a noise coming from what I and the engineer thought to be the motor, but in fact it was the reduction gearbox

[@GoGreenAutos]

Unusual for an Ioniq.

[@Oresti-007]

@@GoGreenAutos after watching your video review i am almost certain that my driving style is the reason

[@judebrown4103]

Lovley jubbley, well done for the further investigations. Enjoyed it.👍👏

[@GoGreenAutos]

Thanks

[@andysmusic4fun]

Really interesting and thanks for the update over part 1. Overall then what intervals do you think for oil changes. I absolutely love my 2020 38kwh and it’s only done 14500 miles

[@Macmonkey1000]

I would do an oil change now if I were you, get rid of the break in particles that will be in there. A change every 50k thereafter should be fine.

[@GoGreenAutos]

I'd say around 50-60K miles. Videos are on the channel showing how to do oil changes.

[@matthewwakeham2206]

I can't imagine much movement of the magnet what with it being oil damped. It's not as if there is much vibration from an EV motor and gearbox. When running there will only be a small amount of oil in the bottom as it will constantly thrown up by the turning of the differential gear. The small amount of flow by gravity presumably runs back over the magnet to the lowest point where it gets picked up by the differential again. I don't think the flow would be enough to buffet the magnet. I did wonder if the plastic gear was some sort of oil pump (if it interfaces with the housing) but a redundant gear for a speedo worm drive seems perhaps more likely (although ancient technology by todays standards). The oil seals on the driveshafts act a bit like an oil pump as far as I'm aware but only to move oil away from the seal and back into the gearbox. The seals have a pattern like the plastic gear moulded into them so that when the driveshaft turns it has the effect of pushing the oil back. I assume that's how it works anyway.

[@Adam-ni5lt]

Having driven a Vauxhall e-Corsa and a Hyundai Ioniq, the Ioniq is certainly slower off the line when you floor it. It feels like Hyundai put a "soft-start" on the motor, which will be better for the gearbox components and should reduce the likelihood of tooth breakage. At first I missed the instant pull of the Corsa-e, but I think the Ioniq will have less chance of mechanical failure in the long run.

[@J0HNM]

Is it possible to get some measurements of the differential set? The TCS in this car does not seem to use the brakes to put power to the ground. Therefore I had the idea that an LSD Diff would, maybe, solve some of my problems driving on slippery surfaces. But planning all this would be much simpler if I knew the dimensions.

[@GoGreenAutos]

The Ioniq only has a 100kW motor, so I can't see why you would consider trying to fit a limited-slip differential. Sure you're not using the wrong tyres for your conditions?

[@J0HNM]

You have a point, but of all cars I have ever owned this car is shockingly bad at hills. Try a small hill with gravel and I can almost not get up. This winter I'm trying all new tires. Continental VikingContact 7. Im hoping it's better. Because this car is perfect in so many other areas. Maybe it's a dumb idea with trying to fit an LSD in the car, but I can't find out if I don't ask the question. :) @@GoGreenAutos

[@cdbuiles]

experiencing similar issue with my LEAF 2020. during slippery conditions, compacted snow (ice) I have had hard time to unstuck/drive my car under slow conditons due to likely similar differential set. the power goes to the wheel with less grip. disabling TC does not help either. I am on X-ICE- tires.

[@sgsuper1150]

I wish we had a video for the VW eup/citigo e/mii. Ive always found lumps of metal in constant mesh scooter gear boxes. They seem to need oil change on the first few services.

[@boredKiwi]

If you happen to have a moment to look, can you remove the input shaft from the motor-side casing half and check to see if there are signs that the ball bearing outer race has been spinning in the aluminium housing?

[@alexk6745]

Many thanks. I have one concern regarding EV gearbox design. I live in Canberra and when I go Batemans Bay on the way back from the ocean we have a very long a steep road. When I drive uphill on my Kia Sorento 2009 Diesel I suspect my gearbox gets hot and the electronics drops down the speed to 20-30km/h and I can't drive any faster for the last 0.5-1km. My question is that I feel that 1 speed gearbox will be a very bad if you have prolonged uphill roads especially if you have high load or towing something. The motor will have to pull hard on low rpms instead of having a decent reduction like 30x1 instead of what you were saying 7.4:1. Is my understanding correct?

[@GoGreenAutos]

I can't see why that would have any effect on an EV gearbox. As you can see, they're a very simple design. The difference here is you're assuming combustion engine characteristics, which are completely different in an EV. A combustion engine requires gears as the engine as a narrow power band, whereas electric motors don't have all the torque from zero rpm.

[@stevejordan4299]

But why did you have to take out the gearbox? I have a 2017 ioniq with a noisy gearbox and wondered if you had the same problem.

[@Peppermint1]

At about min 10:00 you can see there is rotational wear on the outer race of the two bearings - so bearing race would start spinning against the rg case. This may explain the high aluminum contamination in oil on some vehicles. Unclear why the bearing race would start spinning, perhaps the tolerance is too high and the alloy material not strong enough to keep the race fixed under strong accelerations.

[@GoGreenAutos]

There is a "washer" between the bearing and the gearbox case.

[@Peppermint1]

@@GoGreenAutos I noticed, it's like a bracket molded into the casing cast. This bracket is also made of alloy and looking at the image, it also shows the kind of shine caused by the bearing outer race spinning against it. This bracket is machined at the factory, but the shine shows rotational frictions. This may explain why only some vehicles show darkened oil from new - dark color is due to contamination with shaved alloy particles. Perhaps the machining tolerance was not done correctly and bearing is too lose, or the alloy material was not hardened enough on some batches, causing again the bearing outer race to come loose and spin again the bracket.

[@jacobmarx8184]

Great Video as always. I used your videos to help service my old 28kw reduction box and have recently bought a newer 2020 38kw Model after your recommendation. Would you recommend the same shorter servicing schedule with the reduction box and if yes is it the same procedure and oil for the newer model or are the newer models more reliable and don't have to be so concerned? Cheers

[@GoGreenAutos]

Both gearboxes are identical, so no need to treat them differently. An oil change at around 50-60K miles is probably beneficial.

[@patrickh7368]

Interesting to see inside, what was the reason for that gearbox being removed, from on screen viewing it looked ok , accepting the magnet containing some metal … ? Also I can see the lock cone for “park” is on a spring, that means mechanism doesn’t have a hernia if the other end isn’t aligned with a slot…

[@GoGreenAutos]

Good point about the spring on the park pawl. It also means that the park pawl will self engage in a slot when there's some movement in the vehicle to allow it to fall into the next slot.

[@FrancoisEmbrouilleYoutube]

Il y a t’il un risque que ce problème endommage le moteur ?

[@velipekkavahvanen2134]

At 3:40 you can see input shafts end cap that has come loose. (in the pot of intermediate axle) You can see marks it has left on the casing. Bound to have made some noise.

[@GoGreenAutos]

No, these weren't loose when the gearbox was assembled. They've only come loose since this gearbox has been apart and opened up so many times.

[@norbertmolnar6407]

One '"fact" is wrong. The replacing of the reduction gearbox oil is in the service plan, but only advised at 120.000kms. All EU spec Ioniqs have this written in their users manual.

[@GoGreenAutos]

I don't believe this is in the UK version and I've only seen these. Good to know though, thanks.

[@AndyC2_]

Matt, are you still having issues with the low coolant warning on your 38 ? Any updates due please?

[@GoGreenAutos]

No issues. We've had the recall coolant flush job done on both our 38kWh Ioniqs and both have been fine since.

[@dominikhejl5748]

i wonder, if differential is the same as one from an ICE model with mechanical speed sensor, so that nylon ring is drive for it. but you have wheel speed sensors on hubs, so another mechanical sensor doesn't make sense.

[@GoGreenAutos]

The diff maybe the same used in the ICE versions, but they have a completely different gearbox of course. I would add, all cars have wheel sensors...well all cars with ABS brakes.

[@darrensimon6181]

Would you recommend replacing the reduction gearbox oil even if it’s not part of the service plan?

[@GoGreenAutos]

Yes. I've got videos on the channel about this. I'd recommend oil changes about every 50-60K miles, or every 30K on Nissans.

[@darrensimon6181]

@@GoGreenAutos many thanks would you do it on vehicle age or just mileage I have a 2016 Zoe with 38000 miles.

[@GoGreenAutos]

@@darrensimon6181 mileage equals use & wear, so base it on mileage only.

[@darrensimon6181]

I will probably never need to then, many thanks love the videos 👍

[@MePeterNicholls]

Sealed for life - life is often 60/80/100 thousand miles tho. Not “for ever”

[@chemistmanuk]

I presume the speedometer is driven by electronic sensors rather than a cable drive from the gearbox.

[@GoGreenAutos]

Yes. I don't know where from, maybe the wheel sensors. But there's no electrical connection or cable from the gearbox.

[@paulgregory9248]

Hi, now you have explained the operation of the mechanical and not friction method of the hand brakes. So during a mot test is this putting unusual stress on the differential gears? Also this mechanical method of hand brake is the reason for not towing if you have an electrical brake down. I really appreciate your instructive videos. Many thanks, Paul

[@GoGreenAutos]

The handbrake or parking brake is not the same as the park pawl in the gearbox. Hand/parking brakes are ALWAYS frictional brakes on the rear wheels. During an MoT test, when they apply the handbrake on the rolling road, there would be stress on the differential, but then its only for a few seconds and has to be to test the brake force. As for the towing thing...no its not due to the park pawl. You will be unable to tow if it is in Park. But with EVs, the non-towing is due to the electric motor regening while its being towed/spun. So to be safe, there's a blanket rule of no towing allowed. However, if you leave the car switched and and fully running, then it is fine to tow it, as the regenerated energy can be absorbed by the battery and as all the systems are up and running, the car just thinks its driving down hill all the time (and charging).

[@paulgregory9248]

@@GoGreenAutos so do I understand rightly that the pawl is not todo with braking or parking but a safety feature for the motor. In fault condition the drive motor is locked to prevent any uncontrolled drive.

[@GoGreenAutos]

@@paulgregory9248 I think the park pawl is there as its more of a hangover from the traditional automatic gearbox by the OEMs. Its not really required, particularly if the vehicle has an electric park brake (which can be activated automatically). The Renault Zoe ZE50 for example, as done away with it, so you just have Drive, Neutral and Reverse.

[@doohan50000]

The Kona Niro gear noise is because the bearings are made in China. It cannot withstand the torque of the motor and the bearings are damaged, creating noise. If you change the bearings, there will be no noise.

[@theaustralianconundrum]

I desperately want an EV but I cannot get the Australian government to get onboard and reduce the EV tax by $30-40,000 per vehicle. In 2022 they sold 1% of all new vehicles as 100% EV and of those, 80% were expensive Tesla's. In Australia #1 are all ICE diesel SUV's @ 50% of all new vehicle sales.

[@whocares264]

Gearbox are you sure....looks like a differential to me

[@andrewgateway]

It is a transmission unit, that includes a reduction gear and differential.

[@boredKiwi]

The technical term engineers use for any box with gears in it is a "gearbox".

[@thomasadmiral3401]

hi ! did you install out the gearbox?