BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Front suspension clunk/knock

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      09-02-2015, 04:21 PM   #1
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pianoman224's Avatar

Drives: 2008 335i E90
Join Date: Oct 2014
Location: Orange County

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Front suspension clunk/knock

I am experiencing the most annoying knocking noise coming from the front left of the car immediately after hard acceleration. I have searched and searched, but everyone usually has this noise while going over bumps or uneven roads, my issue is only present after I let of the gas.

Whenever I accelerate from 1st or 2nd gear, as soon as I let off the gas (which transfers the vehicle weight forward suddenly) there is a loud audible knock/clunk sound that I can feel under the drivers side floor under my feet. It literally feels like someone took a rubber mallet and hit the floor underneath my feet very hard. It does not happen at higher speeds (my guess is because the g force change is not as sudden and violent as it is at lower speeds). It happens in a single gear so I highly doubt its the gear box. The noise does NOT occur over bumps or rough road, only under the condition described above.

I didn't really have this acceleration knocking/clunk sound until after I started modding the car a year ago with Downpipes, JB4, backend flash, FMIC, Exhaust, and other mods that are very common on this platform.

After installing my downpipes a while ago, I do recall having a similar clunk when I would shift the weight of the car from side to side while turning the wheel in a slalom type manner (if that makes sense, basically at 10-20mph turning back and forth like you were trying to heat the tires up) . BUT, I figured out it was a loose steering rack (I had unbolted it for the downpipe installation). After I tightened them down sufficiently, the noise was gone.

I know that people suggest tightening the top strut nut located under the strut bar in the engine bay, but I have tightened it to no avail, it's as tight as it is going to get.

about 2 weeks ago I decided to replace my sway bar end links with meyle HD links since it was cheap and I figured the stock ones were most likely shot, which they were. Steering felt slightly tighter but the same noise is still there.

Is there anything else I should be checking for suspension wise? upper/lower control arms? Should I be looking at tranny/motor mounts? strut mounts? Honestly, suspension is the one area of this car that I am not familiar with and I have no clue what to look for in terms of proper amount of play in bushings/what bolts to check etc.

Relevant Car Info:

2008 E90 335i AT
FBO mods
Stock M Sport suspension
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      09-02-2015, 08:45 PM   #2
feuer's Avatar

Drives: e90 335i
Join Date: Apr 2015
Location: Chicago, IL

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It could be a lot of things:
Engine mount
Transmission mount
Strut mount
Control arms
Loose subframe
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