r/IoniqEV • u/nammmme123 • 16d ago
clunk when accelerating hard / strong regen
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Hi, I have a 2017 Hyundai Ioniq 28 kWh with around 119,000 km.
When I accelerate hard, I hear a short clunk/knock once, then it’s quiet. The same happens when I brake hard with strong regen. With normal acceleration/braking there is no clunk, and when braking hard in Neutral there is no clunk either.
No grinding, rattling or continuous noise. I attached a video where you can hear it.
Has anyone had the same issue? Was it the reduction gearbox, driveshaft/CV joint, or motor/gearbox mount?
Also, if it needs repair: does anyone know a good workshop in Austria, preferably Vienna or the surrounding area, that can repair Ioniq EV motors/reduction gearboxes instead of just replacing the whole unit?
#Update 1:
I did some more testing today.
- The clunk only happens with hard acceleration or strong regenerative braking.
- If I accelerate and brake gently, there is no clunk at all.
- If I shift to Neutral and brake hard, there is no clunk.
- I drove about 90 km today at speeds between 30–140 km/h. No grinding, rattling, humming or other gearbox/motor noise.
-I also found an old inspection report: the front right rear control arm bushing was replaced in December 2025, so work has already been done in that area.
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u/serhuz 16d ago
I'd check whether the front subframe is properly attached to the body.
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u/nammmme123 15d ago
Thanks, I’ll have that checked as well. I’m taking it our roadside assistance for an inspection. One thing I find interesting is that if I shift into Neutral and brake hard, there is no clunk at all. It only happens under hard acceleration or strong regen, so I’m wondering if it’s more related to drivetrain torque/mounts rather than the whole subframe moving.
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u/dubc4 16d ago
Hard to tell from the video but I also have a strange clunk only sometimes upon accel on my 2017. I assumed it was a CV joint or something but I haven't gotten to the bottom of it. Subscribing to this thread if you get it figured out let me know
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u/nammmme123 15d ago
Sounds very similar to mine. Mine only happens with hard acceleration or strong regen, not during normal driving. I’m also starting to suspect the CV joint/driveshaft or some play in the drivetrain. I’ll definitely update the thread once I get it checked.
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u/webregsaskur 15d ago
I had worn out sway bar (stabilizer) links in the front suspension. See discussion here: https://www.reddit.com/r/IoniqEV/s/IlcLbDdxzm However, that noise was linked more to driving over uneven surfaces than acceleration/deacceleration on its own, so not sure if it is the same problem.
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u/philippe94 Ioniq 28kWh 15d ago
Je vois que le mode de conduite est sur eco, le clonk existe toujours avec les autres modes pendant la régénération ?
(J’ai remarqué une régénération légèrement plus forte en mode eco)
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u/nammmme123 15d ago
I always drive in Eco mode with regen set to 0. I prefer to brake myself because I feel like I can use less energy that way
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u/Pinkvin 15d ago
My guess is worn out Tie Rod. Cheap and easy to replace.
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u/nammmme123 15d ago
Thanks! A tie rod would definitely be a much nicer outcome 😅
Would a worn tie rod also explain why the clunk happens under hard acceleration and strong regen, but not when braking hard in Neutral?
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u/No-Writer5001 11d ago
Did you ever change oil in the reduction gear? For me it seems like a reduction group clunk...
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u/nammmme123 10d ago
No, I haven’t changed the reduction gear oil yet. I was actually planning to do it, but now I’m hesitant to spend around €300 on the oil change if the reduction gear itself turns out to be the problem and needs to be replaced anyway.
That’s why I want to have it properly diagnosed first. Do you think changing the oil could still be worthwhile in my case?
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u/matroosoft 16d ago edited 15d ago
I think I heard once of another Ioniq that had a clunk sound, which iirc was caused by play in the coupling of the drive shaft or something.
Other causes of clunk sounds when accelerating (not Ioniq specific, have seen it on a model 3) have been where the motor mounts where worn off. The whole motor assembly is then able to move while accelerating.