voltamps
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Re: Reduction Gear Oil Change - Benefits for Range

Sun Apr 25, 2021 7:55 pm

denwood wrote:
Sun Apr 25, 2021 11:13 am
Frankly I was surprised that the final drive oil was so thin on the LEAF as I'm quite accustomed to 75w oil being used in differentials on most cars I've worked on. These ICE diffs operate at far lower RPMs, so it's obviously the EV motor drive RPM that is dictating the use of highly engineered fluids. The Audi A3 TDI that I serviced recently had some pretty interesting 75W fluid used both for final drive and DSG trans operation. It also took a laptop and $700 of software to service correctly....249 ft/lbs of torque from that engine at 1200 RPM. So again, it's a bit weird to be putting such low viscosity fluid in what is essentially a differential.

Nissan Matic S - Kinematic Viscosity @ 100°C cSt ASTM D445 5.2

Typical 75w-90 Gear Oil - Kinematic Viscosity @ 100°C cSt ASTM D445 14.56
Not that thick in the Audi A3 TDI DSG transmission. The Audi-VW DSG transmission in the A3 uses spec G 052 182 A2, which has a kv100 6.8, which puts it close to the thin Dexron VI & Mercon LV spec, also close to Nissan Matic S too. I hope you didn't use 75w-90 GL-5 in the DSG by mistake.
https://pim.liqui-moly.de/pidoc/P000247 ... 2.0-us.pdf

The Audi A3 rear differential does use a typical 75w-90 high-viscosity GL-5 gear oil, high-visc & GL-5 due to a Hypoid gear with a lot of sliding friction as it turns rotation 90 degrees. The Leaf doesn't turn rotation vectors 90 degrees at all & hence doesn't need 75w-90 GL-5. ...
Our Leaf's gears & differential are all helical involutes, not Hypoid, and therefore don't use high-visc GL-5 stuff.

A good starting point for understanding why a Leaf gearbox wears more at low-speeds & high torque loads, read the summary below:
https://www.motioncontroltips.com/why-i ... brication/
2020 Leaf SV - sold - I'll get another EV later...Reserved the irresistible Maverick Hybrid, here in a few months
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knightmb
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Re: Reduction Gear Oil Change - Benefits for Range

Sun Apr 25, 2021 9:19 pm

denwood wrote:
Sun Apr 25, 2021 4:51 pm
DougWantsALeaf wrote:
Sun Apr 25, 2021 1:03 pm
So Denwood, are you saying Nissan is actually already pushing the envelope with the stock gearbox oil?
I'm assuming the Nissan engineers have done their homework :-) What I will say is that I would stick to oils that match or exceed the Matic S spec.
Does the ULV exceed but in the wrong way? :lol:
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denwood
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Re: Reduction Gear Oil Change - Benefits for Range

Sun Apr 25, 2021 10:33 pm

Knight, maybe :-)

Volt, I used this stuff. Note the picture is a bit weird but the name was so long, it wrapped half way around the bottle :-)

Image

... and yes you are 100% correct on the kv100 value at 6.8. That was my mistake on the cross reference. The process to change it was a bit painful as you had to fill it the case from underneath, (no dipstick) and then run the car on the hoist, check the trans fluid temp via Rosstech (laptop) and then let it drain on expansion via an overflow tube. The TDI (2010 in this case) A3 is FWD only, so no rear diff. The LEAF differential oil is a whole lot simpler to change :-)

Good point on the hypoid vs helical (I'm no gear expert), however my interest in the oil viscosity was comparing an older transaxle (like the VW 020) which used 75w90, and Nissan final drive which is not so dissimilar (ok, no syncros), using a much thinner oil. Same thing on the DSG transaxle on the A3 TDI as you correctly pointed out...very thin oil. We do have some 90 degree gear action happening in the diff planetary but they are not moving much unless on corners, or spinning in the slippy stuff.

Of course this all illustrates why I truly appreciate the simplicity of an EV after swapping out transmissions, changing clutches, TDI fuel filters, O2 sensors, catalytics, leaky exhausts, timing belt changes, timing chain issues, leaking radiators, worn out starters etc. etc.

rogersleaf
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Re: Reduction Gear Oil Change - Benefits for Range

Mon Apr 26, 2021 9:18 pm

denwood wrote:
Sun Apr 25, 2021 10:33 pm
Of course this all illustrates why I truly appreciate the simplicity of an EV after swapping out transmissions, changing clutches, TDI fuel filters, O2 sensors, catalytics, leaky exhausts, timing belt changes, timing chain issues, leaking radiators, worn out starters etc. etc.
I love this... nothing is more worthwhile about an EV than mechanical simplicity.

If considering the use of slippery stuff additives, my favorite secret sauce has been Dyna-Maxx EP lube concentrate. I've used it in commercial buses and my own cars for over 25 years. I add it to everything from engine oil, trans, wet wheel bearings, diffs, etc.. Never lost a major component since using that stuff. Even had an incident where a turbocharger oil line on a 2-stroke Detroit Diesel failed while cruising at 65 mph where it ran so low the oil pressure shut-downs killed the engine. Fixed the broken line while on the shoulder of the road, refilled the oil and drove it away without any apparent damage to the turbo, or supercharger, or bearings. That engine should have grenaded, was totally amazed. That's what I plan to add to the gearbox oil change on my LEAF.
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denwood
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Re: Reduction Gear Oil Change - Benefits for Range

Tue Apr 27, 2021 7:07 am

Roger, I will admit to not being a fan of additives, other than the odd bottle of injector cleaner. The truth of even injector cleaner is that you can get the same benefit from just running a few tanks of a T1 fuel through.

That said, I know better than to argue :-)

This guy has done some interesting tests, great channel: https://www.youtube.com/c/ProjectFarm/videos

I did a fair bit of travel as a company owner and one thing that always stuck out on the car side were conversations with car service owner/drivers in New York. These guys would often rack up 500 000 miles on a fairly pedestrian vehicle, often with the original engine. The secret there was simple. Oil changes every 3000 miles and fastidious maintenance. As I've taken apart and built up a few engines (along with pretty much every other job, including full paint jobs) it becomes more obvious that careful maintenance is about 98% of the equation. The other 2% I'd say is manufacturing or engineering flaws that you can't really do anything about (depending on the car...some are much worse). I also keep our vehicles a long time.

I would agree 100% that an EV just makes a lot more sense with respect to simplicity :-) I'd also agree 100% that changing out the final drive oil a bit more frequently can only help, and most certainly will not have negative consquences. If you do play with additives in there, I would 100% recommend a few oil analysis to make sure you're not causing damage.

voltamps
Posts: 148
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Re: Reduction Gear Oil Change - Benefits for Range

Wed Apr 28, 2021 4:53 pm

This research study, using a Leaf, assumes the gears lose 3% of the power & energy driving around. ... with Nissan Matic S of course. ....
They lump both tire rolling resistance (rubber flex friction against the road & tire rubber hysteresis) & gear losses into the whole assumed 3% figure, which looks like it could be off a bit.

In the paper, they also show the Coast Down Test (Vehicle Load vs. Speed) graph the EPA did, which reveals the total energy (power) loss due to air drag, tire rolling resistance, the gears, & electric motor windage with support bearings dissipation, all lumped into one big loss.
The EPA threw it into Neutral at some speed, and then let it coast down to zero speed on level ground.

https://www.researchgate.net/profile/Ke ... n-Leaf.pdf
denwood wrote:
Tue Apr 27, 2021 7:07 am
If you do play with additives in there, I would 100% recommend a few oil analysis to make sure you're not causing damage.
Sounds like a good idea. The concern is that any added chemicals to a carefully formulated ATF gear oil might cause foaming (aeration) in all that high-RPM gear spinning, and/or it could interfere with the phosphor-boron EP tribofilm. About you can say about additive chemicals is "It might work, maybe, maybe not....".
Last edited by voltamps on Fri Apr 30, 2021 6:47 am, edited 2 times in total.
2020 Leaf SV - sold - I'll get another EV later...Reserved the irresistible Maverick Hybrid, here in a few months
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SageBrush
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Re: Reduction Gear Oil Change - Benefits for Range

Wed Apr 28, 2021 8:58 pm

denwood wrote:
Tue Apr 27, 2021 7:07 am
As I've taken apart and built up a few engines (along with pretty much every other job, including full paint jobs) it becomes more obvious that careful maintenance is about 98% of the equation.
And 98% of maintenance is ... lubrication of mechanical parts.

My grandfather taught my 8 year old self that lesson. At the time I thought he was slightly BS'g me but I have come to learn just how right he was.
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Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
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goldbrick
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Re: Reduction Gear Oil Change - Benefits for Range

Sun May 02, 2021 8:46 pm

Surely cleaning is part of that 98%. As my neighbor used to say 'clean and lubricate'. That pretty much covers most user-serviceable mechanisms. I'd venture to say it even covers non-moving parts if lubricate stands in for 'oil for corrosion prevention'

voltamps
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Re: Reduction Gear Oil Change - Benefits for Range

Mon May 03, 2021 3:00 pm

Here is a comparison of a Tesla Model S (2015 Sport model), Bolt, & Leaf gears that turn at the same RPM as the wheels, that last big gear.
The width of those gear teeth varies depending on how much torque (teeth force) each has to handle.
The Tesla one is a monster. Even a lot more viscosity couldn't help it much since full torque gets applied at near-zero RPM, a real gear-grinding experience.
Image

It's from the youtube video https://www.youtube.com/watch?v=MQV3D8F6gvw if you want to hear John Kelly's explanations.

The video also shows a Model S (performance model) oil pump inside (no filter on the S) which keeps oil flowing to the gear bearing nearest the motor that turns at up to 17,919 RPM to cool it too. Our Leafs don't spin that fast, so no real need for a pump cooler/lubricater.
Nubo wrote:
Sat Apr 24, 2021 10:49 pm
And there was some kind of "milling noise" problem with the Model S too. So maybe they embraced the habit of over-designing their gearboxes and drivetrains.
I like the part where John Kelly mentions the Silicon Nitride ceramic motor shaft support bearings.
Nubo mentioned the "milling noises" some early Teslas were vexed with, & the ceramic bearings prevent micropitting from the induced current off the motor's fields (or maybe ground current), solving the problem. They are sealed grease bearings on the Tesla and don't share the Dexron VI fluid like the gearbox is bathed in.
2020 Leaf SV - sold - I'll get another EV later...Reserved the irresistible Maverick Hybrid, here in a few months
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LeftieBiker
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Re: Reduction Gear Oil Change - Benefits for Range

Mon May 03, 2021 4:36 pm

I'm guessing that the other reason the Tesla drive is so much more robust is that the Model S is a substantially heavier car than either the Leaf or the Bolt. It has to push against all that additional mass whenever you step on the accelerator, and the harder you step the more force is being applied to it...
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