Clunking Vibration type sound

Well, from that very useful information I can see that the Hyundai/Kia gearbox is virtually identical in design to the Nissan Leaf. The only difference I can see is that ours is missing one locating diameter at the end of the motor shaft spline and there is an added static O-ring seal at the ~80mm dia flange where the dark red area/blue arrow is on the gearbox picture. Between this design and the Nissan, lube oil will more easily access the motor spline via the tail bearing and the hollow pinion shaft, and that can only be good.

Trying to predict potential areas of failure is very speculative without having precise dimensions to carry out a stress analysis, or better, viewing a damaged example. These observations are based on the noise being reported as motor-shaft frequency, that dirty oil has been reported, and what would concern me just from looking at the design if it were my own:
1. First stage pinion shaft (pink):

a) The wall thickness along the entire shaft looks quite thin, especially as it has splines at the motor interface and parking pawl (green thing). Stress cracks could develop in the motor interface's female spline under torque, or be present at the start from production machining stresses on either spline.
b) Normal metal debris from the parking pawl could go straight into the adjacent ball bearing and damage it, if it has an open cage. Often bearings used in manual gearbox applications are equipped with a single shield at the gear side to avoid this problem. That allows oil to enter but not chunks of steel. No shield is shown but the CAD model may not show such a minor detail.​

2. The first and second stage shafts all use ball bearings and will be shimmed at assembly for near zero endplay, just like many other EV gearbox designs. The second stage pinion shaft (in orange) will see minimal end thrust due to the helical gears pushing axially in opposite directions under torque. But the first stage shaft (pink) will see significant end loading under torque, but I can only assume that the bearings are sized to suit. But bearing damage here could deteriorate quickly due to the high RPMs involved.
Excess end play on any of the three shafts will make clicking noises or clunks but only when torque direction changes, or at least not regular in timing. To get a clicking once per motor rev means it has to be at the first stage shaft and from localised damage, either a bent shaft, damaged female spline or if the bearing near that area (arrow b) fails and leaves the motor shaft to support the radial load.

 

Dont assume root cause in the gearbox only. My Niro’s motor was replaced and not the gearbox to address the clicking (gearbox oil was clean). Clicking went away after motor replacement.

 

That's very interesting. My dealer (Langley) insists it is the gearbox and has the part in and booked me for next Tues to do the job. Who is your dealer? Would you mind if I try to get mine to call yours?

 

What is your reasoning as to why the motor caused this? Was it simply that the noise went away?

 

I am really surprised that there still has been no TSB that we know of, and no other acknowledgement from Hyundai as to their understanding of the problem.

 

It's from Niro EV service manual. Same part on the Kona.

So here's why I don't think the gearbox is the problem. Every single case I'm aware of where the owner had his gearbox replaced for the clicking noise, eventually ended up back at the dealer to get the motor replaced. For every case where the motor was first replaced (like my own car), they have not yet returned to get a new gearbox or second motor replacement. I guess it's possible that some cars have both defective motors and gearboxes. You be the judge.

I'm still running the original gearbox and no clicking noise from the new motor with ~4000 miles on it so far. Original motor started clicking at about ~1000 miles and I kept using it until about 4000 miles. Since the motors have failed at many different mileages (one person reported clicking starting at only 100 miles while another at 20000 miles ), I can't say with confidence if the issue has been fully fixed or will eventually return.

 

After the posts referring to the spline connection between motor and gearbox, I'm thinking that connection is the weak link. Maybe the motor side of that connection is slightly less weak?

Sent from my Pixel 3a using Tapatalk

 

The Polish owner whose gearbox destroyed itself is only getting a new gearbox.

 

Correlation of the clicking is not necessarily causation of this failure. It is curious though.

 

My clicking sound started at about 4k miles. It was intermittent at first then at about 7k miles it became persistent. I nearly always hear it when slightly accelerating below 10mph... I am at 11k miles now and the sound is still there. It's not getting worse though. I was scheduled to get it checked early March but did not make it due to the lockdown in socal. I rarely drive the car now anyway. Hope to get it checked once the lockdown is over.

 

I'm in a similar boat. I had my water pump replaced last week, and while the car was in the shop, I told them about the clicking noise. They said they couldn't replicate it and I didn't want to drive around with them due to the whole "social distancing" thing, so I'm putting it off until things get back to normal.

 

Lemme throw this out there as an additional possible factor. For those
of you with the noise, are you aggressive or mellow on your accelerations?
Despite the potential to put some of you in denial, saying "it shouldn't
matter", it would still be nice to generate a table of driving style vs.
ballpark failure onset mileage and how quickly it progressed.

_H*

 

I drive in Eco mode only and my acceleration style is mellow. In fact, the noise is only noticeable when accelerating slowly. First noticed the noise at around 2000 miles.

 

mellow here as well

 

Very mellow here, always in ECO mode. Occasionally do tromp it sometimes if I want to pass on a non-multi lane roadway. Taking mine in tomorrow for the reduction drive replacement.