Driveline Thud

m3_obsession · 06-23-2019, 02:50 PM

Newby here - I just got an e90 m3 with a DCT and about 60k miles. The car works perfectly when it is cold. When its been driven for a while there is a loud thud/clunk when starting off from a stop. It almost feels like the car is being rear ended. No cow bell noise like i've seen when searching the forum or any other symptoms.

Any idea what this could be?

Thanks
Matt

chocstraw · 06-23-2019, 03:57 PM

The DCT is a somewhat clunky transmission coming from a stop, it seems that there is no avoiding it. That being said, it does get clunkier with component wear and age.

Check motor mounts, transmission mounts, the trans-driveshaft flex disk, check the driveshaft for excessive play, and the diff and mounts.

Are shifts hard? On S4, almost all shifts are shock-free, with some having a bit of a jolt

m3_obsession · 06-23-2019, 08:07 PM

Is it normal that the car would start off when cold flawlessly and get worse when hot? I have not checked the motor mounts but maybe they are shot and are worse when the engine compartment gets hot.

The transmission mounts look good, there is minor weeping around the passenger side of the transmission but not at all wet. The trans-driveshaft disk looks to be in perfect condition and the diff seems to have an appropriate level of backlash, the mounts look ok, and the subframe is bolted up tight.

on S4 the shifts are firm but I would consider them shock free, with no abnormal noises.

amrazM · 06-23-2019, 11:01 PM

Could be the car not going into first when stopping then abruptly going into 1st when you get moving.

06-23-2019, 02:50 PM	#1
m3_obsession MCB 1 Rep 10 Posts Drives: e90 m3 Join Date: Jun 2019 Location: Connecticut iTrader: (0)	Driveline Thud Newby here - I just got an e90 m3 with a DCT and about 60k miles. The car works perfectly when it is cold. When its been driven for a while there is a loud thud/clunk when starting off from a stop. It almost feels like the car is being rear ended. No cow bell noise like i've seen when searching the forum or any other symptoms. Any idea what this could be? Thanks Matt
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06-23-2019, 03:57 PM	#2
chocstraw Lieutenant 496 Rep 457 Posts Drives: E92 M3 ZCP Join Date: Apr 2019 Location: Los Angeles iTrader: (0)	The DCT is a somewhat clunky transmission coming from a stop, it seems that there is no avoiding it. That being said, it does get clunkier with component wear and age. Check motor mounts, transmission mounts, the trans-driveshaft flex disk, check the driveshaft for excessive play, and the diff and mounts. Are shifts hard? On S4, almost all shifts are shock-free, with some having a bit of a jolt
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06-23-2019, 08:07 PM	#3
m3_obsession MCB 1 Rep 10 Posts Drives: e90 m3 Join Date: Jun 2019 Location: Connecticut iTrader: (0)	Is it normal that the car would start off when cold flawlessly and get worse when hot? I have not checked the motor mounts but maybe they are shot and are worse when the engine compartment gets hot. The transmission mounts look good, there is minor weeping around the passenger side of the transmission but not at all wet. The trans-driveshaft disk looks to be in perfect condition and the diff seems to have an appropriate level of backlash, the mounts look ok, and the subframe is bolted up tight. on S4 the shifts are firm but I would consider them shock free, with no abnormal noises.
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06-23-2019, 11:01 PM	#4
amrazM mTekMods 2143 Rep 2,902 Posts Drives: like a granny. Join Date: Jan 2010 Location: Manhatan iTrader: (1)	Could be the car not going into first when stopping then abruptly going into 1st when you get moving.
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