How to burn some reduction gear oil...

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knightmb

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Joined
Jan 12, 2015
Messages
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Location
Franklin, TN
Maybe not so much a problem / troubleshooting issue since it takes very specific steps to reproduce it, but I am open to feedback to the more mechanical sage wisdom here.

For a background history, I owned a 2013 SV Leaf for nearly 8 faithful years and finally traded it in a few months ago for a gently used 2020 SL Plus. The Plus part adds the bigger battery pack and higher power motor (maybe the same motor at more power, don't know?) But... when I first got the vehicle, I had a few opportunities to just full power from 0 to 100 MPH (for science!) and the first thing I always noticed was the smell of burning ATF fluid during the top end of the acceleration. I didn't really think much of it because I can do the same thing in many ICE vehicles with an automatic and have in the past. It just chalk it up to abusing the vehicle. Not something one should be doing everyday as it just wears on the transmission unnecessarily.

Oddly enough, I never could achieve this in my 2013, I guess 80 kW just isn't enough to really stress out the reduction gear in the Gen 1 Leaf. Seems Nissan remedied that problem with the Gen 2 :lol:

So.... the point I'm trying to get to. I've been able to reproduce this a few times now (just the luck of traffic that day and no clear law enforcement presence). I did finally just drive back home and check around motor, gear house, tubes, pipes, etc. Basically looking to see if anything was actually leaking anywhere to make the smell. So far I couldn't find anything, no evidence that anything is coming out from either the gear house bolts for changing fluid or anywhere else. I'm in the middle of a gear oil experiment using thinner oil, but I was able to reproduce this before the gear oil change. Today, I still can reproduce the smell, just takes longer before you start to notice the smell (60 mph before gear oil change vs. 80 mph after the gear oil change).

Anyway... back to the point. Is there a type of "pressure" relief on the Gen 2 Nissan Leaf reduction gear house that would let out burning gear oil? That is the question I was trying to get to. :?

Also... has anyone else tried this (on purpose) and noticed any burning oil smell? :shock:
 
I did a highway ramp pull similar to what you're describing during our test drive last month and don't recall a smell. That was in a 2020 SV+ so the same mechanics as your vehicle. It's just one data point though.
 
I'd guess there is some sort of breather hole to allow the trans to equalize the inside and outside pressures, for temperature, altitude, etc.

Before reading the other thread I had no idea that gear oil could get so hot. Interesting stuff...
 
There is a gearcase vent. I frequently use all 160 kW and never notice the smell of burning ATF. I also never noticed it on the previous LEAFs. I will be sending a sample to Blackstone when I get a chance to change the fluid in my 2019 to see how the Matic S is doing--I hope before 36k miles, but need to complete some other projects so I can use my hoist (currently a little over 30k miles). The magnets were really well coated and the Matic S was dark brown when I changed the oil in the 2015 at probably about 60k miles so I think that is too long to wait.
 
When my 2012 was new, I did a few max-speed runs and I did notice a smell after a few minutes at sustained top speed. Not quite "magic smoke", but maybe a mild hint of "magic roast". I just chalked it up to baking off some type of volatile residue from manufacture. As time went on I couldn't reproduce it. There's a a coolant overflow of course but it wasn't a coolant smell.
 
Nubo said:
When my 2012 was new, I did a few max-speed runs and I did notice a smell after a few minutes at sustained top speed. Not quite "magic smoke", but maybe a mild hint of "magic roast". I just chalked it up to baking off some type of volatile residue from manufacture. As time went on I couldn't reproduce it. There's a a coolant overflow of course but it wasn't a coolant smell.

Same for me, never get any smoke and the only way I can smell it briefly; I had the climate control venting outside air to the top vents (so it's basically pointing right at my face / nose) I can get the smell that way. I know the transmission is actually getting hot because when I did this recently, I pulled over at a gas station to look around the engine area shortly afterwards. I felt the gear house, it was hot to the touch, which surprised me. It wasn't flesh burning hot like an ICE engine, but certainly a lot hotter than the what I measured it before when I got readings of +118 F after some long test drives. I'm starting to wonder if I am just burning off something left from the factory when some of the components get hot enough around the motor, gears, inverter, somewhere?
 
Learjet said:
I would think it is the AC drive motor heating up and maybe burning off some production residue.

I've often wondered if I am smelling ozone production from the motor? The smell reminds me of what a laser copier smells like while running.
 
GerryAZ said:
There is a gearcase vent.
I see it, yes a "Hose Breather", costs all of $6.32 . A picture is at:
https://www.nissanpartsdeal.com/parts-list/2018-nissan-leaf/power_train/manual_transmission_transaxle_fitting.html
Lb19N28.jpeg



Probably not burning the ATF fluid. More like smelling a mist churned up like crazy at high speeds. Increase in gear temperature raises pressure inside.
(BTW, is it safe to go 100 mph in a 3,900 lb Leaf Plus extra-heavy, with 16" wheels? The original Ecopias are H-rated anyway, which helps speed margins, thats for sure.)
Nissan must have plenty of reserve fluid quarts inside to account for some escape over time! Their Maintenance Schedule just says to look for leaks, not check the level, although it's a good idea to at least check the level every 75k miles or so due to escape. Or just change it as some of us have, it's easy.

Anybody know if we have a gearbox temperature sensor available on Leaf Spy or Torque etc.?
I haven't tried any of that yet. I've seen this on a C-Max hybrid tranny in the past. When fluid got too low in that one, or any transmission really, telltale temperature goes up a bit. Guessing our Leaf doesn't have gear temperature available, but certainly coolant temperature, which is sort of indirect, given heat transfer into the aluminum housing I suppose.



GerryAZ said:
The magnets were really well coated and the Matic S was dark brown when I changed the oil in the 2015 at probably about 60k miles so I think that is too long to wait.
The brown color may be more the Red Dye breaking down than anything else. It could be long-term oxidation though, I'm not sure. .............With the Leaf, the weakness is lack of a fluild filter, although who wants that extra complexity? Metal wear particles circulating in there are the BIG issue, and those twin magnets help a lot. Blackstone shows some iron floating around that never gets attached, or maybe gets freed from time to time, from the magnets. Hard to get it all out.
 
voltamps said:
With the Leaf, the weakness is lack of a fluild filter, although who wants that extra complexity?
Was that humor, or were you talking about a pump ?
 
voltamps said:
GerryAZ said:
There is a gearcase vent.
I see it, yes a "Hose Breather", costs all of $6.32 . A picture is at:
https://www.nissanpartsdeal.com/parts-list/2018-nissan-leaf/power_train/manual_transmission_transaxle_fitting.html
Oh, that is interesting. Does it feed in anything else or is it just literally facing "down" like in the picture to keep water from creeping in?
 
SageBrush, knightmb, Certainly a filter would also need a pump. A filter+pump is nice to some degree. ... I prefer the simpler no-filter, no-pump, easy to change Leaf system vs. the Tesla Model 3,Y, & Bolt's filter+pump system. ...........Water shouldn't get down that vent pipe.
 
voltamps said:
The brown color may be more the Red Dye breaking down than anything else. It could be long-term oxidation though, I'm not sure. .............With the Leaf, the weakness is lack of a fluild filter, although who wants that extra complexity? Metal wear particles circulating in there are the BIG issue, and those twin magnets help a lot. Blackstone shows some iron floating around that never gets attached, or maybe gets freed from time to time, from the magnets. Hard to get it all out.

From changing regular gear oils, I can say that even normal amounts of wear metals completely change the appearance of the fluid. Gear oil that goes in with a light honey-color, comes out looking silvery gray even at a shortened change interval. The appearance is dependent on the lighting. In some light it appears nearly clean and other lighting makes it look like silvered paint. And this effect is from the tiny particles that escape the magnets. I'd liken it to the StarLink satellites that are visible from the ground at night, despite their diminutive size and great distance.

Since magnetic drain plugs have been deemed sufficient "filtration" for gearboxes in the billions, they must do a fair job of removing critical contaminants even though they leave particles of less consequence in suspension. No filtration is perfect. What's the payback for a more complex system? I'd be curious to know how much better a media-filtered system is at extending service life of comparable gearboxes. Maybe there's some data out there from industrial applications. I guess it's also worth considering that the larger particles that DO get caught by the magnets spend some time circulating before finding themselves in capture distance of a magnet. I'd love to hear the opinions of a mechanical engineer on this topic.
 
knightmb said:
Learjet said:
I would think it is the AC drive motor heating up and maybe burning off some production residue.

I've often wondered if I am smelling ozone production from the motor? The smell reminds me of what a laser copier smells like while running.

I'd say mine tended towards "warm electrical components", if that makes any sense. Maybe motor windings?
 
Nubo said:
No filtration is perfect. What's the payback for a more complex system? I'd be curious to know how much better a media-filtered system is at extending service life of comparable gearboxes. Maybe there's some data out there from industrial applications. I guess it's also worth considering that the larger particles that DO get caught by the magnets spend some time circulating before finding themselves in capture distance of a magnet. I'd love to hear the opinions of a mechanical engineer on this topic.

Filtration is very good at getting wear rates down, especially important in the more powerful Tesla motors that put high pressures on the gear faces. Tesla must have finally concluded a filter was worth it. The oil system pump is there to promote better gear cooling, important since the Tesla Model 3 goes 140 mph. That fast & heat is incredible in there. With a pump for cooling, might as well put in a filter, as it could also save a few warranty claims along the way when bigger metal chunks occasionally appear in a few units. ...... My 1st degree was in Mech Engineering, but I've mostly worked aerospace & software after the 1980s, not gears. Others have more recent kinematics & gear design mech experience than me if they are on this non-tech forum anyway.
 
knight, is the smell before or after you put the ULV fluid in the gearbox? I have not been able to get any smells out of the leaf, so either you are slightly over filled or the ULV fluid is behaving differently and foaming up or something to make it out of the breather vent.

Marko
 
estomax said:
knight, is the smell before or after you put the ULV fluid in the gearbox? I have not been able to get any smells out of the leaf, so either you are slightly over filled or the ULV fluid is behaving differently and foaming up or something to make it out of the breather vent.

Marko

Both. It did it before and after. It seems to take more effort to make it happen with the ULV in it, but given a big enough hill and a long enough stretch to run full power for over +10 seconds and I can get the smell to come out. Oddly enough, tried to do it again today (put a paper-towel around the end of the breather to see if it would catch anything) and was not able to reproduce. It was hot today, much more so than the other days, so I'm at a loss.

I did try an experiment of purposely burning some of the ULV in the oven (wife hates me) to see if it was what I was smelling, didn't smell the same. It does smell like a combo of fresh transmission oil (not burning) and that ozone smell you get from electronics (like a laser printer for example)
 
i've only once had diff oil come through the breather and that was the rear diff on my 240sx after i did a few 0-120 runs, haven't seen it happen otherwise and it didn't really smell either. The oil in our gearbox doesnt even get that warm as you proved, so i am betting the smell you are smelling is from the inverter area rather than the gear oil.

Marko
 
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