[BimmerNugget]

I have a 2011 328i RWD auto transmission 59k miles.

My car starts and idles 100% fine. However, when I put car into Drive and give it a little gas there is a very slight raspy grinding noise when accelerating. This only happens the first time I gas it when I start the vehicle.

For example, I start my car, let it idle until revs drop below 1k. Then I put into drive and take off. That is when I hear the raspy grinding sound. If i let go of the gas and get on it again there is no noise. Basically this sound will never come back again until the car sits overnight and I start it again the next time.

I have ruled out any engine issues because when the car is in park and I rev it, it does not make the grinding sound. The engine sounds 100% smooth. Only when I am actually in drive and moving. So that leads me to think it's a transmission related issue? Should I get a transmission fluid flush done at 59k miles?

[desertman123]

How long does the noise last? How loud, and where's it coming from. If you can manage to catch a video that'd help a ton.

I'm thinking it's more some random drivetrain or suspension piece is loose or something. I'd just take a good look at everything and shake it around and make sure everything's okay.

Also at 60-80k is a good time to get trans and differential fluid done anyway. Don't bother with flushes, just a drain and fill.

[SiEgs90]

Maybe a heat shield? I have a 328xi. I get a slight rattle from time to time under about 2krpms. I have a very slight hill grade turning onto my street and that's when I usually hear it. I never received any fault codes so I'm not too worried. Cosmetically though it does sound like a piece of junk when it does act up. Sounds almost like a set of tools being dragged along the pavement. Been meaning to get it looked at, but it hasn't annoyed me enough yet.

[BimmerNugget]

The noise literally lasts 3-4 seconds tops when I give it gas for the first time. When I let off the gas or brake for a stop sign, then go again, the grinding sound is not there.

This only happens when the car has sat for 6+ hours AKA when car is "cold".

[JuniorB]

Check your exhaust system for anything that may be loose. Best way I find is go under the car and start banging all the pipes, converters, and muffler with a dead blow hammer. It will give a destintive sound when something is loose. Because the exhaust is one piece, it's tied up there pretty tight. It's hard to say where to pinpoint, but I would try that first. Your issue sounds like it's only under acceralation only. You can also hold the brake and throttle at the same time, bring the rpms, you should find it if it's the exhaust.

[Noir]

Originally Posted by SiEgs90

Maybe a heat shield? I have a 328xi. I get a slight rattle from time to time under about 2krpms. I have a very slight hill grade turning onto my street and that's when I usually hear it. I never received any fault codes so I'm not too worried. Cosmetically though it does sound like a piece of junk when it does act up. Sounds almost like a set of tools being dragged along the pavement. Been meaning to get it looked at, but it hasn't annoyed me enough yet.

Heatshield was my problem, sounded particularity nasty too. I honestly thought I ruined my new clutch at the time heatshield was making contact with the driveshaft.

[Ngy]

Had this and it was the propshaft support bearing had collapsed.

[thatpolygon]

I had a metallic rattle noise when taking off too and it was a loose o2 sensor.