SOLVED! Knocking/clunking from the tunnel

Michael Oxman

Michael Oxman

The Journey Begins!
So for the last few weeks I've heard a knocking/clunking sound coming from the back of the car, usually while accelerating between 1st, 2nd and 3rd. At first I thought it was something in the trunk but it's not. It almost reminded me of the sound of a cracked u-joint but it is a random knocking pattern and not rhythmic like the u-joint and feels like whatever is knocking might be vibrating too. I thought it might be something loose with the exhaust but that's solid.

It's gotten more frequent to the point that it knocks on acceleration but also when going over rough road or bumps at speed. It was very prominent tonight, and when I gripped the tunnel between the seats as I was driving it certainly felt like whatever was knocking was knocking around in there, but as I understand it that's just the coolant pipes - no moving parts. I wonder if its possible for a pipe to come loose? Anyway, I'm going to put it up on some ramps to take a look and I was wondering if anyone had any insight into what to look for. I'm positive its not coming from the engine or transmission.
 
Check all three engine mounts to see if they look like the rubber has broken down. Check the bolts holding the CV joints, they have been known to back out. Look at the axles and CV to see if you can spot any rubbing. Check the lollipop to see if it is still in one piece. The lollipop controls the motion of the shift rod which passed thru the tunnel. If it fails I guess the shift rod could be bouncing around a bit.

In short, lots of things could come loose and cause a knocking sound.
 
As per this thread it sounds like I'll need to check the transmission mounts as well. that whole thread also talks about the drive shaft.

Strange CV joint / diff / transmission noise.

Hi all, I just got back to Munich from Zurich (about 350 KMs) and I seem to have a bit of a problem. On the way there, I noticed a "clunking" sound coming from the back of the car (right hand side) whenever took a slow, sharpish right hand curve (such as a curved exit or entry ramp). I made a...
xwebforums.com
 
The mechanical bits in the upper tunnel would be the shifter, which usually would not be moving around while in gear, and the emergency brake pull mechanism.
 
UPDATE: I'm up on ramps and I see the inner CV joint is touching the cross member. As per this post, I fail the pencil test completely. Upon further inspection, I'm missing a bolt holding up the transmission!! Anyone know the bolt dimensions??

Odd rhythmic clunking coming from the rear of the car.

So I took the second test drive after working on some of the issues the first ride uncovered and this time I noticed a rhythmic metallic clunking sound come from the back of the car, it sounded like the passenger side but I can not be sure at this time. It increased in frequency as the car...
xwebforums.com

And this is me:
 

Attachments

  • Knocking.jpg
    Knocking.jpg
    139.8 KB · Views: 121
  • Bolt.jpg
    Bolt.jpg
    125.1 KB · Views: 125
Last edited:
My guess is the missing bolt is not why the CVJ is hitting the crossmember. A worn lower mount is more likely the cause. So while you are under there check the condition of the rubber on the mount. There are several threads discussing this.
 
Dr.Jeff said:
My guess is the missing bolt is not why the CVJ is hitting the crossmember. A worn lower mount is more likely the cause. So while you are under there check the condition of the rubber on the mount. There are several threads discussing this.
Click to expand...
It looked ok to me, and the reason why I'm looking at the bolt is you can see that there is a drop of a few millimeters between the hole in the transmission and the hole on the crossmember. I'll have to jack up the tras a bit just to replace it once I figure out what goes in there.
 
JimD said:
You are missing a bolt.
View attachment 66946
Click to expand...
Thanks Jim - I found that I was missing it this morning, so the remaining question is what actually goes in there. Do you know? I started a separate thread with the question thinking that it would get more eyes. Thanks in advance.

Your underneath is so clean - it looks better than new.
 
Michael Oxman said:
It looked ok to me, and the reason why I'm looking at the bolt is you can see that there is a drop of a few millimeters between the hole in the transmission and the hole on the crossmember. I'll have to jack up the tras a bit just to replace it once I figure out what goes in there.
Click to expand...
Sorry, I could not see that gap in the pic. And it sounds like replacing the bolt fixed it.....

Michael Oxman said:
Success!! M8x1.25 25mm
Click to expand...
Glad to hear. ;)
 
ok the front fastener is supposed to be a stud with a nut, the rear on a bolt...the reason being if you put a bolt in the front one, and it's too long it might pierce the casing into the tranny....ouch, lol...
 
Kevin Cozzo said:
ok the front fastener is supposed to be a stud with a nut, the rear on a bolt...the reason being if you put a bolt in the front one, and it's too long it might pierce the casing into the tranny....ouch, lol...
Click to expand...
Defintitely. I should have said nut, not bolt.
 
Michael Oxman said:
Looks like the back fastener was loosening up too. Snugging up the front bolt pulled the whole thing over a few millimeters and I got a few turns on that other bolt as well. No more clunking!
Click to expand...

Ummm...it almost sounds like you do not realize that there are THREE fasteners holding that engine mount on !!! As there is also of course another bolt on the rear of the mount up top. So there is one stud on the front of the mount...and two bolts on the rear. Perhaps you did not look hard enough to see that other rear bolt up higher as it is kinda hidden from your view when looking up ? and perhaps it is loose or missing ?

Engine mount ext bracket install 03.JPG
 
Last edited:
You must log in or register to reply here.
Back
Top