Clunk! during hard braking-- drivetrain motion related?
 

My '04 has an elusive noise that only occurs when I brake very hard on a bumpy, undulating road surface. It is a very loud BLAM! like metal on metal.

It only happens in situations like this: I'm threshold braking or ABSing over the top of a small rise in the road. Then I reach the bottom of the "dip" (still braking hard) where the next rise starts immediately. The BLAM happens when the front end reaches the start of the next rise. Again, hard on the brakes the whole time. Oh, this is all with stock tires, driving hard on a (really gnarly) paved canyon road.

At first I assumed I was in the front bumpstops during full compression at the bottom of the dip, but there is no associated ricochet or dramatic movement. Just the BLAM sound. If I was out of travel and bottoming out the front susension (Vishnu spec Ohlins coilovers), the car would jerk or bounce at that corner, and/or the steering wheel would tug. It is not doing that at all so I am fairly confident I am not running out of travel. Also there is no coil bind.

I checked the front subframe & underbody to see if they were smacking the pavement but they are unscathed.

Another evom member has experienced this in his '03, even when stock. Same deal, no dramatic movements, just a loud clunk during hard braking. He recalled that others on evom had found it was related to engine or drivetrain motion rather than suspension motion. As if an engine mount was "bottoming out" or some other accessory banging into something else, but he couldn't recall exactly what. He also said it went away with time (maybe it's self-clearancing?).

I searched and came up with no clues. Has anyone else experienced this, and what is it?

Hm, no takers yet...

Does this noise sound familar to anyone?

Check your motor mounts and suspension bushings.

I've heard this on my brand new JDM Evo IX as well... on a highway, if i do an emergency stop (one time a fool suddenly pulled out in front of me) i heard a loud *CLUNK*.

My girlfriend reckons its something in my boot moving forwards and hitting, so you might want to check that... I dont hear that sound normally, not even when doing Auto-X or roadracing, so I'm not sure where that sound comes from as I don't reproduce it normally (and don't want to purposely do it over and over in case it is hurting something).

Check your boot as my gf suggests :)

hahaha your tools are loose in the spare well

Good theory, but my trunk is completely stripped of everything-- spare, jack, first aid kit, flares, porn collection, even the carpet. And the noise is definitely coming from the front. I'll check the motor mounts first.

Dont know if this means anything but I remember Toyota had a problem like this a while back and the found it to be mfg. tolerances in the calipers and pads causing a click sound when the breaks are applied.

I've heard this on pretty much every autox I've done. This is not the mild clunk mentioned on this thread:
https://www.evolutionm.net/forums/sh...ighlight=clunk

I have that clunk too. But this loud clunk seems to be triggered by extremely hard braking. And once it's happened once it continues for the rest of the day. At the last autox once it started, it started clunking on every single transition through the slalom! I thought I wouldn't be able to get home without the car falling apart, but as expected the noise hasn't happened since.

dont brake very hard on a bumpy, undulating road surface.

im pretty sure i have heard this noise too im gonna have to check it out

Im having that noise as well atm.. but I discovered that the guys who replaced my clutch and stuff - didnt tighten everything.. so I ran it over and fixed everything, it dont clunk anymore.. so check everything..

However, I have a strange Plastic like clunk noice when I deaccelerate(sometimes) and drive over dome bumpe roads(most of the time)... sometimes in some turns as well, but Ive tested it by turning really really hard at high speeds and no noice at all.. so I dont think its my steering.. any ideas?

I had the same problem with my '03 and it was attributed to drivetrain movement, not suspension. Both of the driveshaft carrier bearings were shot and allowing too much play in the driveshaft. It doesn't seem like there could be any connection between the two and when I first was investigating the problem at home I saw the bearings were shot but thought in no way they could be related.

Even though the bearings were covered under warranty I bought and replaced them myself because I don't trust the guys at Mitsu and the clunk went away. I have no idea if you have the same problem but the symptoms are the same.

Good luck {thumbup}

This might sound lame, but what about your exhaust? My friend's exhaust knocks against the underside of this G35, somewhere and we cant figure it out. Its not a BLAM but an annoying knocking when he goes over bumps and so on.

Good luck

I had an issue for a little while with my downpipe hitting my support bar in certain situations, worth a check, and easy fix.

This might be exactly what is happening to mine. I went on the lift last Saturday and checked everything out to try and diagnose this clunk noise. I noticed there was some shaft play, but didn't have another evo there to compare to...I am going to check that out when I get the chance this weekend.

Thanks!