reduction gear replacement

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J

jsteve

Active member
Joined
Dec 26, 2021
Messages
34
Location
Hillsboro, OR
Hi All,

I'm picking up my Leaf today after it has been at the dealership for over a week. I took it there asking for diagnosis of why there was an occasional pink fluid under the car. My car is a 2022, so pretty new and to be honest this makes me wonder if this is a bad omen for my car already.

But it's all being replaced as a warranty repair, so no out of pocket expense (not even for the the rental of the loaner car) as far as I know. I'll for sure when I pick up my car today.

So, you experts here what exactly is the reduction gear? I'm assuming this is a part of the transmission? And does replacement of it mean I should anticipate other transmission troubles down the line?

Also, any ideas of what could have caused this need for replacement in the first place?

Note, the fluid leak wasn't consistent. Some days there was a 2 inch, stain on the white paper towel I kept renewing each day I took it out of the garage. Other days it was more like 6 inches. Before the white paper towel and the first time I noticed a leak there was a lot more fluid. The leak seemed more liquid-y than viscous like oil.

I also didn't take it immediately upon noticing the leak, since on some days (after the white paper towel placement) there was no stain on the paper towel. I don't understand the rate of leak. But I would say it wasn't ever "gushing".

I do hope I didn't cause permanent damage to the transmission or other parts of the car from waiting.

But the dealership didn't hesitate to replace the reduction gear and from the get-go described this as a warranty repair.

Also, looking for posts relating to reduction gear on this website before making this post, I saw a lot of discussion on reduction gear oil but nothing on reduction gear replacement. So maybe this isn't a common occurrence?

Should I be worried that this need to replace this means I'm in store for worse in terms of corrective maintenance on my new Leaf?

Also, the "pink fluid" leak I was seeing - is this an oil then?

Thanks!
--jan
 
The reduction gear changes the RPM's of the motor to the RPM's required to turn the axles. It is the transmission in a Leaf. I've never heard of one being replaced but since it has been replaced I wouldn't worry about the transmission - you have a new one.

The red fluid is the oil that lubricates the gears in the unit. Since it was leaking there was probably not enough oil left inside and that is why the whole unit was replaced. I'd say it is more likely that they simply put in an entire new unit rather than open it up and try to replace only parts of it. So it should be completely new and good to go.
 
/\ Agree. It is likely that an oil seal failed and the reduction gear 'ran dry' and damaged itself because of the lack of oil. Without knowing how hard it is to replace just the one gear and the oil seal I won't say whether or not I think they replaced the whole unit. I hope so, because the smaller gear(s) that meshes with the reduction gear would likely also be worn..
 
The electric motor can spin at upwards of 14,000 rpm. You wouldn't want to hook the wheels up directly to that, so there are gears to bring down the rpm, and also bring up the torque. It's not a transmission in the normal sense of the word, since the gears are permanently engaged and the ratio never changes. And so it's more accurately called a "reduction gearbox". It is a much simpler mechanism than a standard transmission.

The leak was oil, specifically ATF (automatic transmission fluid) is used as the lubricant in the gearbox, hence the red color.

The leak was likely either a defective seal, or perhaps a defect in the casing. Differences in the leak from day to day could be the result of temperature, air pressure, etc...

I wouldn't worry about reliability going forward.
 
The corollary to this question is: you can change/replace the reduction gear fluid with something a bit newer/different (like Valvoline ULV), resulting in a slight increase in overall efficiency (m/kWh). This isn't for everyone (but not hard to do), and lots more info can be found if you search the forum for threads on the subject. I did it last year (first and only time in my 10 year ownership) and am very happy with the results.
 
Nubo said:
The electric motor can spin at upwards of 14,000 rpm. You wouldn't want to hook the wheels up directly to that, so there are gears to bring down the rpm, and also bring up the torque. It's not a transmission in the normal sense of the word, since the gears are permanently engaged and the ratio never changes. And so it's more accurately called a "reduction gearbox". It is a much simpler mechanism than a standard transmission.

The leak was oil, specifically ATF (automatic transmission fluid) is used as the lubricant in the gearbox, hence the red color.

The leak was likely either a defective seal, or perhaps a defect in the casing. Differences in the leak from day to day could be the result of temperature, air pressure, etc...

I wouldn't worry about reliability going forward.
Click to expand...

Thank-you! I find the idea of a 1 speed transmission intriguing. Interesting that perhaps the differences in things like temp, air pressure, etc. may have an impact on why sometimes it leaked and other times it did not.

Thank-you for your reply.
 
LeftieBiker said:
/\ Agree. It is likely that an oil seal failed and the reduction gear 'ran dry' and damaged itself because of the lack of oil. Without knowing how hard it is to replace just the one gear and the oil seal I won't say whether or not I think they replaced the whole unit. I hope so, because the smaller gear(s) that meshes with the reduction gear would likely also be worn..
Click to expand...

Does it sound like the whole transmission was replaced or just some "gearbox"? Thanks for your reply!
 
goldbrick said:
The reduction gear changes the RPM's of the motor to the RPM's required to turn the axles. It is the transmission in a Leaf. I've never heard of one being replaced but since it has been replaced I wouldn't worry about the transmission - you have a new one.

The red fluid is the oil that lubricates the gears in the unit. Since it was leaking there was probably not enough oil left inside and that is why the whole unit was replaced. I'd say it is more likely that they simply put in an entire new unit rather than open it up and try to replace only parts of it. So it should be completely new and good to go.
Click to expand...

Thanks for your reply! I'm glad that the experts here feel that in likelihood this issue was taken care of in a complete fashion through full replacement. This is reassuring.
 
HI Again All,

So also perplexing to me is with all the tech and firmware that must be in this car which leads me to believe that there are a fair number of sensors and some kind of onboard diagnostic system - it is surprising to me that I never got any indication from the screen or dashboard that something was wrong. My only symptom was the fluid leak and if weren't for parking in my garage on a fairly level and plain colored floor I wouldn't have noticed the leak for sometime.

When I suffered a flat tire in this car (drove through a new home construction zone and picked up a screw) - the TPMS system let me know right away with no doubt! Plus my tire was low enough that "something just felt wrong" and it sure was. I didn't make it more than 20 feet before I pulled the car back into the driveway.

For something like the transmission subsystem - it's seems that a sensor should have triggered a message to the onboard computer. Something like an ODM signalling the dasboard?

Anyhoo my car's notification system was silent. Not even an old fashioned "idiot light" :)
 
Stanton said:
The corollary to this question is: you can change/replace the reduction gear fluid with something a bit newer/different (like Valvoline ULV), resulting in a slight increase in overall efficiency (m/kWh). This isn't for everyone (but not hard to do), and lots more info can be found if you search the forum for threads on the subject. I did it last year (first and only time in my 10 year ownership) and am very happy with the results.
Click to expand...

Thanks for your reply. I'll ask what kind of transmission fluid they filled it up with when I pick up my car in an hour.
 
jsteve said:
HI Again All,

So also perplexing to me is with all the tech and firmware that must be in this car which leads me to believe that there are a fair number of sensors and some kind of onboard diagnostic system - it is surprising to me that I never got any indication from the screen or dashboard that something was wrong. My only symptom was the fluid leak and if weren't for parking in my garage on a fairly level and plain colored floor I wouldn't have noticed the leak for sometime.

When I suffered a flat tire in this car (drove through a new home construction zone and picked up a screw) - the TPMS system let me know right away with no doubt! Plus my tire was low enough that "something just felt wrong" and it sure was. I didn't make it more than 20 feet before I pulled the car back into the driveway.

For something like the transmission subsystem - it's seems that a sensor should have triggered a message to the onboard computer. Something like an OBD signalling the dashboard?

Anyhoo my car's notification system was silent. Not even an old fashioned "idiot light" :)
Click to expand...
 
jsteve said:
LeftieBiker said:
/\ Agree. It is likely that an oil seal failed and the reduction gear 'ran dry' and damaged itself because of the lack of oil. Without knowing how hard it is to replace just the one gear and the oil seal I won't say whether or not I think they replaced the whole unit. I hope so, because the smaller gear(s) that meshes with the reduction gear would likely also be worn..
Click to expand...

Does it sound like the whole transmission was replaced or just some "gearbox"? Thanks for your reply!
Click to expand...

Again, without knowing how hard it is to replace just the one gear and the oil seal I won't say whether or not I think they replaced the whole unit.
 
jsteve said:
LeftieBiker said:
/\ Agree. It is likely that an oil seal failed and the reduction gear 'ran dry' and damaged itself because of the lack of oil. Without knowing how hard it is to replace just the one gear and the oil seal I won't say whether or not I think they replaced the whole unit. I hope so, because the smaller gear(s) that meshes with the reduction gear would likely also be worn..
Click to expand...

Does it sound like the whole transmission was replaced or just some "gearbox"? Thanks for your reply!
Click to expand...

Theres nothing in the service manual related to opening the case or dealing with internals so I expect they just replace as an assembly. Here's a video if you're interested in what the thing looks like.

[youtube]https://www.youtube.com/watch?v=L5WhB7uQLzY[/youtube]
 
LeftieBiker said:
Given the dealership model of "Replace assemblies until fixed" it does seem likely that the whole unit is now new.
Click to expand...

Thanks LeftieBiker!

The service adviser guy that handled the return of my car on Friday wasn't a 100% sure on my question regarding "was the whole transmission replaced". But there was a page in the paperwork showing an illustration of the unit that made it look like the whole thing was replaced. He wasn't going to give me a copy of the illustration page and said so, but another service adviser who overhead said it was okay for me to have a copy, so the guy checking me out made me a copy of it. I wanted a copy of the "bill" too they were sending to Nissan for the warranty repair but was denied. I had to sign all these pages, but only got to have copies of a few pages. Most of the pages just had text descriptions but no $$ amounts, only the word "warranty". Make sense since it was a warranty thing. But at least I have some itemization of the repair.

The repair for this "reduction gear replacement" ran almost $4k (according to the page I signed but was not allowed a copy of). And the guy said that was "cost". So undoubtedly more if it was "retail". Very glad that this was a warranty replacement and that the dealership didn't blink in making this repair.

I'm SO HAPPY to have my car back. I missed it greatly :D The loaner "rental" they gave me for 8 days sucked. It was a new Nissan Altima (a "fine" car in its own way) but did not have that EV feel that I've come to enjoy. But very interesting is the Altima nomenclature was very similar to my Leaf. I guess new cars, heck anything in the last 5-7 years is very different that what I'm used to. Prior to my 2022 Leaf, I drove a 1998 BMW 318ti for 23 years and I was quite used to the lack of "tech" :D Things like backup cameras and infotainment systems. I'm not so sure I like all of this stuff (yet?). But I do like the Android Auto integration with my phone when it works.
 
jsteve said:
Does it sound like the whole transmission was replaced or just some "gearbox"? Thanks for your reply!
Click to expand...

The reduction gear and the differential are combined in one alumin(i)um casing, and they are, together, almost all the transmission. The rest is of it is the two drive shafts and constant-velocity joints to connect the differential to the drive wheels. The whole of this reduction gear with differential is only about 20 kg/45 pounds weight, a few inches wide to the left of the traction motor, and together they are the bottom slice of the three-layer lump in the engine compartment. Two of the three motor+transmission mounting brackets are fixed to the reduction gear casing.

There's an old thread over at speakev.com where an owner replaced a faulty reduction gear, outdoors, with the car on axle stands and a home-made timber prop to hold up the motor, inverter and power delivery module while its support brackets were disconnected. No power lift or specialized garage equipment! Based on the description there, Nissan will have replaced the transmission, not tried to repair it while you were waiting.

The reduction gear also contains the parking lock, which is mechanically operated. Reverse, neutral and drive are not 'gears' in the LEAF (or the e-NV200), just electronic control modes. Even in neutral, the motor spins with the front wheels. Compared with a conventional manual or automatic transmission, the reduction gear is tiny, simple and reliable.
 
Thank-you woeful for a great explanation of the reduction gear! So far so good. No more "pink" fluid on my garage floor and my Leaf is running great :D Thanks. --jan

p.s. also funny coincidence - I just today discovered the speakev.com site :D
 
My 2023 Leaf S suffered a transmission failure at 10 months and 8,900 miles. The first indication was a loud whine as the leak was not apparent, possibly due to random parking places.
Dealer diagnosed "Fluid leak at union to traction motor, low fluid level burnt smelling and there is metal debris in fluid"
Repair: Replace Transaxle/Gearbox

Dealer ordered new assembly and installed under warranty, and furnished rental car for the week.

I purchased the Leaf at dealer located 40 miles from Nissan Symrna factory and got it right off the delivery truck 12/08/2022. This was at the end of the Covid chip shortage and shortage of new vehicles.

I hope this is a rare occurrence 5 years after the original OP had their problem. The parts and labor must cost Nissan a lot of dollars.
 

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ddansb01 said:
I hope this is a rare occurrence
Click to expand...
Rare but not super-rare, as far as I can tell. Nissan's service manual makes a meal of the replacement (remove entire power stack from the drive shafts to the power delivery module) where independent garages and at least one DIY owner can support the stack then remove just the reduction gear and drive shafts from below. That needs far less work and fewer use-once parts to replace.
 

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