Thud from rear

Ryan_n · 05-21-2018, 08:57 AM

I’m slightly worried about what happened yesterday with the car. I was at a stop and started accelerating pretty hard but another car started to get on my line so I quickly let go the throttle while I was accelerating and I hear a pretty loud thud in the back, I was sure the transmission or diff broke. I kept driving in S2 Sport+ and did not feel anything wrong with the car. I got home, parked for 20mins and took it for another drive (normal and spirited..) but still the car felt normal and gear changes were normal. Where did that thud come from, is it normal after a hard release of throttle under accel?

Thanks for your help guys

JayZap16 · 05-21-2018, 09:13 AM

Quote:

Originally Posted by Ryan_n

I’m slightly worried about what happened yesterday with the car. I was at a stop and started accelerating pretty hard but another car started to get on my line so I quickly let go the throttle while I was accelerating and I hear a pretty loud thud in the back, I was sure the transmission or diff broke. I kept driving in S2 Sport+ and did not feel anything wrong with the car. I got home, parked for 20mins and took it for another drive (normal and spirited..) but still the car felt normal and gear changes were normal. Where did that thud come from, is it normal after a hard release of throttle under accel?

Thanks for your help guys

Its hard to say if the thud was caused by the letting go of the throttle. What did the thud sound like? Metal on metal? Hard bushing noise? Meaning, it could be coincidence that you rear wheel hit a pot hole at the exact same moment you let go a of the throttle.

mkoesel · 05-21-2018, 09:14 AM

Sounds like driveline backlash. Hard to say that's it for sure, but if it is, there should be nothing to worry about unless you find that the car keeps doing it regularly even when not letting off the accelerator abruptly.

Ryan_n · 05-21-2018, 09:43 AM

Thank you for the quick replies. I'm sure it was a loud thud in the trunk area not very metallic I can't recall but no potholes on the street where I was.

I took it for a drive again this morning and there is nothing that sounds wrong or drives wrong. @mkoesel, that driveline backlash seems to be it. I tried to reproduce it by releasing throttle during acceleration and didn't hear thud or clunk. However, I didn't do an instant/abrupt throttle release on purpose like when I heard the thud.

When the thud happened it was really an abrupt throttle release. Seemed like the trans was going to shift up and I went from 75% throttle input to 0% in an instant. Is this thud a 'normal' tolerance with the trans or diff?

theox05 · 05-21-2018, 02:52 PM

Might sound like a dumb Q, but did you have anything in your trunk? I've started/stopped quickly with my work bag in the trunk and it will definitely make a thud when it falls over.

Nikolas · 05-21-2018, 02:53 PM

Quote:

Originally Posted by theox05

Might sound like a dumb Q, but did you have anything in your trunk? I've started/stopped quickly with my work bag in the trunk and it will definitely make a thud when it falls over.

Body?

theox05 · 05-21-2018, 02:55 PM

Quote:

Originally Posted by Nikolas

Body?

Nah, I'm always careful to strap those down. Last thing I need is blood on that fine BMW carpeting.

Ryan_n · 05-21-2018, 03:54 PM

Hahaha no body or anything in the trunk. I’m going to keep monitoring it but for now it seems nothing was affected, car is driving solid and smooth. But, if anyone can confirm it’s ok or normal-ish, I’d probably sleep better tonight. I know I shouldn’t care so much for a car but this is an M3 I’m sure you guys understand..

Poiseuille · 05-21-2018, 04:27 PM

Quote:

Originally Posted by Nikolas

Quote:

Originally Posted by theox05

Might sound like a dumb Q, but did you have anything in your trunk? I've started/stopped quickly with my work bag in the trunk and it will definitely make a thud when it falls over.

Body?

nah, that guys from Colorado, not Philly.

Whatcoloristhat · 05-21-2018, 05:35 PM

Quote:

Originally Posted by Ryan_n

Hahaha no body or anything in the trunk. I’m going to keep monitoring it but for now it seems nothing was affected, car is driving solid and smooth. But, if anyone can confirm it’s ok or normal-ish, I’d probably sleep better tonight. I know I shouldn’t care so much for a car but this is an M3 I’m sure you guys understand..

my mechanic noticed it right away on a new m3 6mt...normal perhaps considering it doesn't happen often?

drjoe66 · 05-21-2018, 08:56 PM

I get this once in a while too. Accelerate hard and then let go off the gas. Thud from rear axle. Also sometimes when I get off the accelerator at higher rpms, like on the freeway it makes that sound. Not reproducible though and my 2015 DTC never did this.

MarbleNY · 05-21-2018, 09:02 PM

I too have heard that sound when I let go of the gas abrubtly. I've only had the car a week, but i've heard it twice yesterday on a long hard drive.

jmg · 05-21-2018, 11:15 PM

I've heard this on my DCT. I googled it and at the time I read it was somewhat normal and not to worry about it if it goes away.

Aaaaaaaaa · 05-22-2018, 12:16 AM

Heard it a few times on my 6MT when letting gas off too abruptly in Sport+ and hard acceleration. From what I've read M diffs/trans are just noisy plus the decreased sound insulation in these cars.

prodigymb · 05-23-2018, 10:05 AM

Quote:

Originally Posted by Poiseuille

nah, that guys from Colorado, not Philly.

I've heard the sound as well . . . but I am from Philly

SocalBM · 05-23-2018, 11:02 AM

My car does it as well and it's got fewer than 200 miles on it (just delivered). 6 speed car.

AllForTheCash · 05-23-2018, 05:59 PM

Mine does it at times as well. Just as described above. 6MT.

Deteria · 05-24-2018, 09:11 PM

Maybe a loud wheel hop thud?

sprokai · 05-24-2018, 09:30 PM

Quote:

Originally Posted by AllForTheCash

Mine does it at times as well. Just as described above. 6MT.

I hear an occasional thud in my 2015 DCT. It's drive line lash. Not the greatest noise, but I think it's normal. I had worse in my old STi and even my old Yamaha FJR shafty was pretty bad.

BMWM3ekim · 05-31-2018, 10:25 AM

I have heard it as well (I have DCT), but more so during slowing down (coasting down to a stop light for example). Seems to occur most frequently in second gear - I liken it to the sound you might hear with manual transmissions when you let out the clutch too quickly while car is in gear when slowing down... I've experienced it numerous times during the 45000 miles of my 2016's life..

Antartic · 12-06-2018, 08:39 AM

I heard this earlier today- I was driving in manual mode (2018 F80 DCT), and downshifted from 2nd to 1st to come to a stop- heard such a loud thud that I had to pull over thinking either someone hit me or I broke the differential.

The car drove fine afterward, but no amount of insulation would've muted that noise- it was loud and you could feel it too. I tried to replicate the driving conditions but didn't hear and feel the thud again. I can't take it to the dealer if I can't replicate it. I'm thinking this might be just a quirk of the car.

YasF80_SLO · 12-08-2018, 10:17 AM

when im on the power with the DCT in any gear and simultaneously upshift manually, and let of the gas during the gear change ( or slightly before) it makes a very firm thud and bang, much more so than a normal not WOT upshift would be. either more power or lower gear makes it worse.

also when driving around with the windows open its pretty easy to hear the differential. it also makes some noises that are pretty odd.

05-21-2018, 08:57 AM	#1
Ryan_n New Member 35 Rep 12 Posts Drives: 2017 M3 F80 ZCP Grey Black Join Date: Mar 2016 Location: Montreal iTrader: (0)	Thud from rear I’m slightly worried about what happened yesterday with the car. I was at a stop and started accelerating pretty hard but another car started to get on my line so I quickly let go the throttle while I was accelerating and I hear a pretty loud thud in the back, I was sure the transmission or diff broke. I kept driving in S2 Sport+ and did not feel anything wrong with the car. I got home, parked for 20mins and took it for another drive (normal and spirited..) but still the car felt normal and gear changes were normal. Where did that thud come from, is it normal after a hard release of throttle under accel? Thanks for your help guys __________________ F80 2017 M3 ZCP \| Grey Black and SO \| Ultimate Package
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05-21-2018, 09:14 AM	#3
mkoesel Moderator 7512 Rep 19,368 Posts Drives: No BMW for now Join Date: Jun 2006 Location: Canton, MI iTrader: (1)	Sounds like driveline backlash. Hard to say that's it for sure, but if it is, there should be nothing to worry about unless you find that the car keeps doing it regularly even when not letting off the accelerator abruptly.
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05-21-2018, 09:43 AM	#4
Ryan_n New Member 35 Rep 12 Posts Drives: 2017 M3 F80 ZCP Grey Black Join Date: Mar 2016 Location: Montreal iTrader: (0)	Thank you for the quick replies. I'm sure it was a loud thud in the trunk area not very metallic I can't recall but no potholes on the street where I was. I took it for a drive again this morning and there is nothing that sounds wrong or drives wrong. @mkoesel, that driveline backlash seems to be it. I tried to reproduce it by releasing throttle during acceleration and didn't hear thud or clunk. However, I didn't do an instant/abrupt throttle release on purpose like when I heard the thud. When the thud happened it was really an abrupt throttle release. Seemed like the trans was going to shift up and I went from 75% throttle input to 0% in an instant. Is this thud a 'normal' tolerance with the trans or diff? __________________ F80 2017 M3 ZCP \| Grey Black and SO \| Ultimate Package
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05-21-2018, 02:52 PM	#5
theox05 Private 83 Rep 64 Posts Drives: 2016 GT4 Join Date: Jan 2018 Location: CO iTrader: (0)	Might sound like a dumb Q, but did you have anything in your trunk? I've started/stopped quickly with my work bag in the trunk and it will definitely make a thud when it falls over.
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05-21-2018, 03:54 PM	#8
Ryan_n New Member 35 Rep 12 Posts Drives: 2017 M3 F80 ZCP Grey Black Join Date: Mar 2016 Location: Montreal iTrader: (0)	Hahaha no body or anything in the trunk. I’m going to keep monitoring it but for now it seems nothing was affected, car is driving solid and smooth. But, if anyone can confirm it’s ok or normal-ish, I’d probably sleep better tonight. I know I shouldn’t care so much for a car but this is an M3 I’m sure you guys understand..
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05-21-2018, 08:56 PM	#11
drjoe66 Captain 329 Rep 757 Posts Drives: 2021 M5 & 2019 X3 Join Date: Nov 2008 Location: Carolinas iTrader: (0)	I get this once in a while too. Accelerate hard and then let go off the gas. Thud from rear axle. Also sometimes when I get off the accelerator at higher rpms, like on the freeway it makes that sound. Not reproducible though and my 2015 DTC never did this. __________________ 2019 X3 2021 M5 Comp On order: 2022 X3M40i
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05-21-2018, 09:02 PM	#12
MarbleNY Enlisted Member 31 Rep 49 Posts Drives: 2018 Sapphire Black M4 ZCP 6MT Join Date: May 2018 Location: NY iTrader: (0)	I too have heard that sound when I let go of the gas abrubtly. I've only had the car a week, but i've heard it twice yesterday on a long hard drive.
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05-21-2018, 11:15 PM	#13
jmg Lieutenant General 18697 Rep 14,115 Posts Drives: G82 M4C X-Drive Join Date: Mar 2013 Location: Orange County, CA iTrader: (1) Garage List 2022 G82 M4C X-Drive [9.85] 2018 F80 M3 CS [9.87] 2019 i3 BEV [0.00]	I've heard this on my DCT. I googled it and at the time I read it was somewhat normal and not to worry about it if it goes away. __________________ 2022 G82///M4 Competition X-Drive - KW-HAS, EBC Bluestuff, Millway Race Camber Plates, Cup2 Connect, PSI High Flow Midpipe, Lightweight Front Lip, M Perf Flow Through Wing Previous • 2018 F80 ///M3 CS • 2016 F80 ///*M3 IG: Raging_G82
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05-22-2018, 12:16 AM	#14
Aaaaaaaaa Banned 7559 Rep 5,056 Posts Drives: The other M3 Join Date: Oct 2014 Location: So Cal iTrader: (0)	Heard it a few times on my 6MT when letting gas off too abruptly in Sport+ and hard acceleration. From what I've read M diffs/trans are just noisy plus the decreased sound insulation in these cars.
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05-23-2018, 11:02 AM	#16
SocalBM First Lieutenant 179 Rep 348 Posts Drives: Porsche GT3 Join Date: Nov 2013 Location: Houston iTrader: (0)	My car does it as well and it's got fewer than 200 miles on it (just delivered). 6 speed car.
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05-23-2018, 05:59 PM	#17
AllForTheCash Private 28 Rep 75 Posts Drives: M5 Comp Join Date: Aug 2015 Location: East Coast iTrader: (0)	Mine does it at times as well. Just as described above. 6MT. __________________ 2015 911 Carrera 4S 7MT 2018 911 GT3 6MT 2019 BMW M5 Comp
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05-24-2018, 09:11 PM	#18
Deteria Second Lieutenant 110 Rep 216 Posts Drives: 2015 M4 Join Date: Mar 2017 Location: Dallas iTrader: (0)	Maybe a loud wheel hop thud? __________________ 2015 Black Sapphire F82 M4: Bootmod3 Stage 1 Tune / GTS DCT TCU DIFF Flash / Remus Catback / VRSF Charge & J Pipe / MST Intakes / Mishimoto TMIC / RK Autowerks Crank Hub / Apex VS-5RS 19x9.5 ET22 19x10.5 ET45 / Powerflex Bushings / MSS HAS / Evolve x Bilstein B6 Damptronic / Vorshlag Camber Plates / Hotchkis Sways
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05-31-2018, 10:25 AM	#20
BMWM3ekim New Member 10 Rep 9 Posts Drives: '16 AB M3 Join Date: May 2015 Location: Bridgewater, NJ iTrader: (0)	I have heard it as well (I have DCT), but more so during slowing down (coasting down to a stop light for example). Seems to occur most frequently in second gear - I liken it to the sound you might hear with manual transmissions when you let out the clutch too quickly while car is in gear when slowing down... I've experienced it numerous times during the 45000 miles of my 2016's life.. __________________ 16 F80 M3 AB DCT ZEC ZLP 2VZ 2VF
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12-06-2018, 08:39 AM	#21
Antartic Second Lieutenant 94 Rep 293 Posts Drives: F80 M3 2018 Join Date: Sep 2010 Location: USA iTrader: (0)	I heard this earlier today- I was driving in manual mode (2018 F80 DCT), and downshifted from 2nd to 1st to come to a stop- heard such a loud thud that I had to pull over thinking either someone hit me or I broke the differential. The car drove fine afterward, but no amount of insulation would've muted that noise- it was loud and you could feel it too. I tried to replicate the driving conditions but didn't hear and feel the thud again. I can't take it to the dealer if I can't replicate it. I'm thinking this might be just a quirk of the car.
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12-08-2018, 10:17 AM	#22
YasF80_SLO Captain 232 Rep 649 Posts Drives: F80 Join Date: Oct 2016 Location: San Luis Obispo iTrader: (0) Garage List 2015 BMW M3 [0.00] 2018 Nissan Versa S [0.00]	when im on the power with the DCT in any gear and simultaneously upshift manually, and let of the gas during the gear change ( or slightly before) it makes a very firm thud and bang, much more so than a normal not WOT upshift would be. either more power or lower gear makes it worse. also when driving around with the windows open its pretty easy to hear the differential. it also makes some noises that are pretty odd.
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