Thud when taking foot off gas at higher speeds

sauceonside · 07-12-2017, 04:37 PM

I'm noticing an issue where I'm not sure if this is normal or an issue. I have a RWD M240i with 3500 miles. I've started noticing a sensation that is most noticeable at higher speed in 6th gear.

The steps to reproduce are:
-Drive car at 75mph in 6th gear, say around 3000 RPM
-Take foot off gas quickly

Almost instantly after foot is off the gas, I can feel a momentary pulsation/shake/thud. It feels as if the power is detaching even though it is not in neutral. It is almost instant but especially noticeable at higher speeds and suddenly removing gas. I do not feel it if being gentle laying off the gas.
I can feel this through the steering wheel and seat and hear a very faint noise at the same time.

In the reverse situation, going from coasting to giving sudden gas, I feel the same thing. It again feels like there's a moment where the driveshaft power is being restored before to the wheels. Definitely not a slipping issue but feels like it's coming from the rear as opposed to engine.

Has anyone experienced this or have any ideas if this is normal behavior? I don't recall if this has always been the case but only in the past 500 miles noticed it. Thanks for any help.

wdc330i · 07-12-2017, 06:01 PM

Quote:

Originally Posted by sauceonside

I'm noticing an issue where I'm not sure if this is normal or an issue. I have a RWD M240i with 3500 miles. I've started noticing a sensation that is most noticeable at higher speed in 6th gear.

The steps to reproduce are:
-Drive car at 75mph in 6th gear, say around 3000 RPM
-Take foot off gas quickly

Almost instantly after foot is off the gas, I can feel a momentary pulsation/shake/thud. It feels as if the power is detaching even though it is not in neutral. It is almost instant but especially noticeable at higher speeds and suddenly removing gas. I do not feel it if being gentle laying off the gas.
I can feel this through the steering wheel and seat and hear a very faint noise at the same time.

In the reverse situation, going from coasting to giving sudden gas, I feel the same thing. It again feels like there's a moment where the driveshaft power is being restored before to the wheels. Definitely not a slipping issue but feels like it's coming from the rear as opposed to engine.

Has anyone experienced this or have any ideas if this is normal behavior? I don't recall if this has always been the case but only in the past 500 miles noticed it. Thanks for any help.

It would help to know what driving mode this happens in.

sauceonside · 07-12-2017, 06:04 PM

Quote:

Originally Posted by wdc330i

It would help to know what driving mode this happens in.

This occurs in any driving mode, including Comfort and Sport.

Y0tsuya · 07-12-2017, 06:08 PM

May be the engine twisting back to rest position. The thud is when it bottoms out on the engine mounts. There was a youtube video that shows extreme effect of this with worn-out engine mounts.

Not really noticeable when my car was new but starting to show up now. Will probably get louder over time.

sauceonside · 07-12-2017, 06:10 PM

Quote:

Originally Posted by Y0tsuya

Probably the engine twisting back to rest position. The thud is when it bottoms out on the engine mounts. There was a youtube video that shows extreme effect of this with a worn-out engine mounts.

Not really noticeable when my car was new but starting to show up now. Will probably get louder over time.

Ok that's good to know. It sounds like you're doubting it's any kind of defect- let me know if that's not necessarily the case. Thank you.

morphomeman · 07-12-2017, 06:20 PM

But this is a 2017 vehicle! The engine mounts should be solid as rocks. Maybe time to visit your friendly dealer people.

overcoil · 07-12-2017, 07:25 PM

in the 235 at 3500 rpm you start to produce some real power and I guess I feel a pulse when getting on the throttle and when rapidly lifting - but no thud.

Are the engine mounts on the 240 electronic ?

moldcad · 07-12-2017, 11:53 PM

OP hears/feels it from the rear, so I'd suspect the driveshaft connection with the differential.

Piotr

3rdcoast228i · 07-13-2017, 06:30 AM

That sounds more intense than it should be... I would definitely take it to the dealer to make sure everything is ok.

Why risk more damage if something is wrong? As forum members we are just guessing, we can't feel what you are talking about.

bimmerfile · 07-13-2017, 06:56 AM

Quote:

Originally Posted by 3rdcoast228i

That sounds more intense than it should be... I would definitely take it to the dealer to make sure everything is ok.

Why risk more damage if something is wrong? As forum members we are just guessing, we can't feel what you are talking about.

Definitely agree. Based on OP's description of the issue, a service technician will have no problem reproducing the noise OP is hearing/feeling - so leave it to the experts to evaluate/resolve.

Maynard · 07-13-2017, 11:03 AM

Another vote for taking it in for diagnostics - if it is a driveshaft issue you really don't want it to cut loose at speed. Also wondering about that dual mass flywheel and if that has anything to do with it - have heard that some of those go bad, but no idea what symptoms go with the failure.

XutvJet · 07-13-2017, 01:10 PM

Pretty normal. My 6mt does this in 6th at highway speeds. That thud is driveline lash between all the motor, tranny, and diff mounts. Pretty common on rwd cars, especially more luxury focused ones where they're trying to quell NVH. I noticed this at around 1,000 miles and it hasn't gotten worse in 20 months and 16k miles of driving.

07-12-2017, 04:37 PM	#1
sauceonside Private 31 Rep 68 Posts Drives: 2017 240i MT Join Date: Jul 2016 Location: Metro-West iTrader: (0)	Thud when taking foot off gas at higher speeds I'm noticing an issue where I'm not sure if this is normal or an issue. I have a RWD M240i with 3500 miles. I've started noticing a sensation that is most noticeable at higher speed in 6th gear. The steps to reproduce are: -Drive car at 75mph in 6th gear, say around 3000 RPM -Take foot off gas quickly Almost instantly after foot is off the gas, I can feel a momentary pulsation/shake/thud. It feels as if the power is detaching even though it is not in neutral. It is almost instant but especially noticeable at higher speeds and suddenly removing gas. I do not feel it if being gentle laying off the gas. I can feel this through the steering wheel and seat and hear a very faint noise at the same time. In the reverse situation, going from coasting to giving sudden gas, I feel the same thing. It again feels like there's a moment where the driveshaft power is being restored before to the wheels. Definitely not a slipping issue but feels like it's coming from the rear as opposed to engine. Has anyone experienced this or have any ideas if this is normal behavior? I don't recall if this has always been the case but only in the past 500 miles noticed it. Thanks for any help.
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07-12-2017, 06:08 PM	#4
Y0tsuya Second Lieutenant 77 Rep 261 Posts Drives: 2015 M235i 6MT, 2016 340i 8AT Join Date: Jun 2015 Location: SF Bay Area iTrader: (0)	May be the engine twisting back to rest position. The thud is when it bottoms out on the engine mounts. There was a youtube video that shows extreme effect of this with worn-out engine mounts. Not really noticeable when my car was new but starting to show up now. Will probably get louder over time.
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07-12-2017, 06:20 PM	#6
morphomeman Major 595 Rep 1,220 Posts Drives: 2015 M235ix Join Date: May 2015 Location: United States iTrader: (1) Garage List 2016 BMW X3 [0.00] 2015 BMW M235ix [0.00]	But this is a 2017 vehicle! The engine mounts should be solid as rocks. Maybe time to visit your friendly dealer people.
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07-12-2017, 07:25 PM	#7
overcoil Major General 3081 Rep 5,580 Posts Drives: M235i 6spd Join Date: Dec 2013 Location: Mid-Atlantic iTrader: (0)	in the 235 at 3500 rpm you start to produce some real power and I guess I feel a pulse when getting on the throttle and when rapidly lifting - but no thud. Are the engine mounts on the 240 electronic ?
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07-12-2017, 11:53 PM	#8
moldcad Major 266 Rep 1,091 Posts Drives: M235i Join Date: Jan 2013 Location: Poland iTrader: (0)	OP hears/feels it from the rear, so I'd suspect the driveshaft connection with the differential. Piotr __________________ previous: 2003 E46 330i SMG just sold: 2013 F10 528i xDrive my AWD beater: 2015 Golf R mk7 DSG my RWD pirate & long-distance cruiser: 2015 M235i AT8, LSD
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07-13-2017, 06:30 AM	#9
3rdcoast228i Captain 225 Rep 610 Posts Drives: 2016 228i Msport Join Date: Apr 2017 Location: Texas iTrader: (0)	That sounds more intense than it should be... I would definitely take it to the dealer to make sure everything is ok. Why risk more damage if something is wrong? As forum members we are just guessing, we can't feel what you are talking about.
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07-13-2017, 11:03 AM	#11
Maynard Colonel 3862 Rep 2,882 Posts Drives: 228iX & M2C Join Date: Mar 2016 Location: Upstate NY iTrader: (1)	Another vote for taking it in for diagnostics - if it is a driveshaft issue you really don't want it to cut loose at speed. Also wondering about that dual mass flywheel and if that has anything to do with it - have heard that some of those go bad, but no idea what symptoms go with the failure.
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07-13-2017, 01:10 PM	#12
XutvJet Major General 5596 Rep 5,391 Posts Drives: 2011 Cayman Base, 2016 M235 Join Date: Mar 2016 Location: Kansas City iTrader: (-1)	Pretty normal. My 6mt does this in 6th at highway speeds. That thud is driveline lash between all the motor, tranny, and diff mounts. Pretty common on rwd cars, especially more luxury focused ones where they're trying to quell NVH. I noticed this at around 1,000 miles and it hasn't gotten worse in 20 months and 16k miles of driving.
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