Thud from rear under hard acceleration

jh_f30 · 09-02-2018, 11:29 AM

Hey guys! I've noticed a thud coming from the rear when I do some pulls. Typically under low rpm/high torque loads. It's a single thud with a slight shudder and then it's gone. I haven't determined if it only happens in a specific gear. It doesn't sound like it's very good for the car, so I don't really want to try replicating it over and over again.

I'm wondering if it's possible that either A) the trans slips the gear before catching or B) it's a single wheel hop as the tires catch.

Anyone else experience anything like this? I think I'm pretty much done with mods at this point as my mileage is getting pretty high and it's my daily driver. I'm due for a transmission fluid change, but if it's wheel hop, I might also consider trying some Bilstein B8s in the rear (my shocks are probably pretty worn anyways).

obert · 09-02-2018, 11:50 AM

Complete guess here........bad driveshaft flex disc?

BEAR-AvHistory · 09-02-2018, 01:06 PM

Car bottoming suspension on acceleration squat with some wheel hop?

jh_f30 · 09-02-2018, 01:49 PM

Also forgot to mention, I notice it happening mostly when rolling on, ie. getting onto an on ramp and hitting about 3/4 throttle to accelerate to highway speed (and then some).

Haven't done a launch from a standstill in a while, so I don't know if it would cause the same thud, but given the unknown nature of the sound, I think I'll refrain from launches until it's resolved.

09-02-2018, 11:29 AM	#1
jh_f30 Lieutenant Colonel 1308 Rep 1,827 Posts Drives: 2013 335i Sportline Auto RWD Join Date: Aug 2017 Location: Bay Area, CA iTrader: (2)	Thud from rear under hard acceleration Hey guys! I've noticed a thud coming from the rear when I do some pulls. Typically under low rpm/high torque loads. It's a single thud with a slight shudder and then it's gone. I haven't determined if it only happens in a specific gear. It doesn't sound like it's very good for the car, so I don't really want to try replicating it over and over again. I'm wondering if it's possible that either A) the trans slips the gear before catching or B) it's a single wheel hop as the tires catch. Anyone else experience anything like this? I think I'm pretty much done with mods at this point as my mileage is getting pretty high and it's my daily driver. I'm due for a transmission fluid change, but if it's wheel hop, I might also consider trying some Bilstein B8s in the rear (my shocks are probably pretty worn anyways). __________________ 2013 F30 335i RWD ZF Melbourne Red ~Remus Sport Axleback~VRSF Chargepipe~VRSF Catless Downpipe~GPlus FMIC~HR Sport Springs~Active Autowerke OBD Flash Tune Stage 2~
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09-02-2018, 11:50 AM	#2
obert Brigadier General 1781 Rep 4,456 Posts Drives: 2013 328i Join Date: Oct 2011 Location: Seattle Wa iTrader: (49)	Complete guess here........bad driveshaft flex disc?
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09-02-2018, 01:06 PM	#3
BEAR-AvHistory 2020 Z4 M40i - 2022 M4C Convt 3129 Rep 5,264 Posts Drives: 2020 Z4 M40i - 2022 M4C Convrt Join Date: Jun 2011 Location: Raleigh, NC - OIB, NC iTrader: (0) Garage List 1965 COBRA (FFR rep ... [8.57] 2023 Jeep Wrangler ... [9.50] 2009 Yamaha V-Star [0.00] Cars 2-BMW, 2-FORD, ... [0.00] 2023 Ford Expeditio ... [0.00] 2020 Z4 M40i [10.00] 2022 BMW M4C [7.25] 1998 FORD Ranger 4X4 [0.00]	Car bottoming suspension on acceleration squat with some wheel hop? __________________ Kevin Dravit Gray, Black Leather, Moonlight Roof, Red Calipers 2022 M4C - 2020 Z4 M40i - 2023 FORD Expedition XLT Max 4X4 400BHP - 2009 V-Star - 1998 Ranger 4X4 5MT - 1965 Cobra (R) 5MT - 2023 Jeep Wrangler Sport S 6MT
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09-02-2018, 01:49 PM	#4
jh_f30 Lieutenant Colonel 1308 Rep 1,827 Posts Drives: 2013 335i Sportline Auto RWD Join Date: Aug 2017 Location: Bay Area, CA iTrader: (2)	Also forgot to mention, I notice it happening mostly when rolling on, ie. getting onto an on ramp and hitting about 3/4 throttle to accelerate to highway speed (and then some). Haven't done a launch from a standstill in a while, so I don't know if it would cause the same thud, but given the unknown nature of the sound, I think I'll refrain from launches until it's resolved. __________________ 2013 F30 335i RWD ZF Melbourne Red ~Remus Sport Axleback~VRSF Chargepipe~VRSF Catless Downpipe~GPlus FMIC~HR Sport Springs~Active Autowerke OBD Flash Tune Stage 2~
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