[DynamoDan]

Hi all,

Finally made the step up to a 235i. It's a 64 plate with low milage (29k). Ever since I have had it there is a quiet grinding noise on acceleration coming from I'd guess the drivers footwell.

It's under warranty and been to a dealership 3 times. First time I was told it was a characteristic of the car, second time I was told it was the gearbox. I picked up my car with the new gearbox to just turn back round and drop it off again the sound had not changed one bit.

It's still with bmw but the suggestion is it's "normal" but I wouldn't class this sound as anything to do with the gearbox. (gearbox whine)

So the sound:

Metalic
Slightly resonating sound
Sounds rotary
Sound seems to either disappear or quieten down so I cant hear it when I left off the gas
Happens only in gear
Between particularly revs 1.5k - 2.5k maybe
Doesn't happen initially only after a few turns out of my area
Sound doesn't change as gears change. Constant and doesn't stop
Really slow acceleration to those revs means it doesn't happen
Not heard it in reverse
Apparently bmw have put mics on the car and suggests from gearbox.

Any idea what it could be? Tried recording the sound but the mperformance exhaust and engine just get picked up.

My best idea so far is that something is maybe catching the drive chain gently. I. E parking break Clip but my knowledge of cars is awful!

Thanks in advance!

[tlum235i]

Sounds like the drive shaft center support. Only reason I know this is I just saw a YouTube video with a guy who had this issue on his BMW and it sounds very similar.

[DynamoDan]

Yeh that's what thought too from a couple of videos. Bmw are saying the new gearbox does it but within tolerance and only in one gear which isn't true. Going back to pick up the car later but will mention it.

If it was the gearbox I'd expect the sound to vanish briefly while it changes gear not be constant throughout

[aerobod]

One known issue is a broken handbrake cable support clip in the tunnel above the driveshaft that allows the handbrake cable to scrape on the driveshaft. Cheap to fix the clip, but labour cost can be high due to generally having to remove the exhaust and driveshaft to fix.

[DynamoDan]

So I've got the car back. The sound they heard which resulted in the new gearbox isn't the one I've been hearing. The best way to describe it is when you run a wet finger over a wine glass. Not really a grind actually but a resonating high pitched sound. It's getting louder as I drive it as my phone picks it up if I put it near the drivers footwell. Doesn't happen until warmed up then gets worse. Link below to a recording

https://easyupload.io/phnlkj

[tlum235i]

I can't really tell much from the audio unfortunately. Could be a few things honestly. I know wheel bearings can cause humming noises, so if the sound is near the footwell, maybe that's it. Not sure that would make much sense though if it's lower mileage.

[DynamoDan]

Yeh I did think wheel to begin with but it seems to disappear totally or be extremely quiet once I let off the gas. Seems worse in lower gears so assuming its related to the power being pushed on or to the engine

[Devils41]

If its under the arm rest and sounds like this video its the E-brake clip. its plastic and is prone to breaking. It allows the ebrake cable to rub the driveshaft underload. I had a Mechanic replace mine with a CNC'd one, they only needed to drop the fuel tank a bit.

[DynamoDan]

It's the front drivers side. I'm going to ring bmw again tomorrow and see what the crack is. I have a massive rattle under my car after it's been driven a bit, near drivers side.

I reckon the nosie could be something simple but we will see.

[icekxd]

Hi, sorry to bump a relatively old thread but seems like this same issue applies to me. I am at 83k miles, 2015 spec.

I first noticed this sound a few months ago but it was only noticeable when driving off after cold start (out of bay parking driving forward with the windows down) I could only hear the noise because of the cars that were besides mine. Once the engine reached operating temps I wouldn't hear this noise again.

However, now I can hear it all the time. I can drive down the road at city speeds, engine warmed up, outside temperature at around 90°F with windows down whenever I gently accelerate I will hear this noise. I will try grab an outside recording and post it here.

I am certain it isn't the handbrake clip as I also have that issue and the two sounds are completely different and from different locations.

Thanks in advance

Originally Posted by DynamoDan

So the sound:
Metalic
Slightly resonating sound
Sounds rotary
Sound seems to either disappear or quieten down so I cant hear it when I left off the gas
Happens only in gear
Between particularly revs 1.5k - 2.5k maybe
Sound doesn't change as gears change. Constant and doesn't stop
Really slow acceleration to those revs means it doesn't happen
Not heard it in reverse

[DynamoDan]

Mine turned out to be a cheaper aftermarket air filter. Have the bmw one now and all good. Even had the gearbox replaced by bmw 😢

[icekxd]

Originally Posted by DynamoDan

Mine turned out to be a cheaper aftermarket air filter. Have the bmw one now and all good. Even had the gearbox replaced by bmw ��

Glad you got it sorted buddy.

It's hard to believe that the air filter made a metallic noise. Unfortunately, that's not the case for me as I do have the OEM one and I had this issue before replacement.

I started to worry that it might be the chain guides or the chain itself stretched out, but this would mean that this noise would be present all the time even in neutral, yet it isn't.

[DynamoDan]

Originally Posted by icekxd

Glad you got it sorted buddy.

It's hard to believe that the air filter made a metallic noise. Unfortunately, that's not the case for me as I do have the OEM one and I had this issue before replacement.

I started to worry that it might be the chain guides or the chain itself stretched out, but this would mean that this noise would be present all the time even in neutral, yet it isn't.

Telling me, they had it 4 times, one new gearbox and one new airfilter later and its gone or quiet enough to not hear it constantly in low acceleration. It only did it after about 2 minutes of driving but must be when it starts dragging in cold air or something. The noise was never there in neutral or park. Mine sounded like a metal disc rubbing noise but must have been the wind/air being taken in. The turbo did sound awesome with it in but rather have the normal one I was expecting and no noise

[Breakfirstfinishlast]

Originally Posted by icekxd

Glad you got it sorted buddy.

It's hard to believe that the air filter made a metallic noise. Unfortunately, that's not the case for me as I do have the OEM one and I had this issue before replacement.

I started to worry that it might be the chain guides or the chain itself stretched out, but this would mean that this noise would be present all the time even in neutral, yet it isn't.

You never know with aftermarket parts.. BMW puts a lot of money into R&D when they build things. There's no way a small aftermarket can engineer as well as BMW does. I've had similar experience with aftermarket parts. Not the grinding you're talking about. Specifically one aftermarket air box was actually reducing the power of the car.