Novelty goat

Boomtubes went on my '08 GT convertible today. Loud, deep, has that old time boat sound at idle, amazing at high rpms. They drone a bit, but not too bad, easy to live with. Better than Macs.

Here is my issue (aside from the absolutely worthless clamps and an alignment issue, replaced the clamps already);

when the exhaust has heated up, there is a god awful rattle coming from somewhere. Sometimes a banging sound, other times a metal on metal buzz, other times a "marbles in a can" rattle. But I have no clue from where. Everything is tightened down, nothing appears to be touching, but I cannot live with this. I drove the car tonight, got it warmed up again, checked everything while hot, and still see nothing that looks like it could be causing this issue.

Oh, and weirdly, with the top down you can barely hear the rattling.

Has anybody experienced a similar problem? If so, how did you remedy it?

theedge67

Check the hangers on the mufflers. I had a similar problem and found it to be the rear hanger on the driver side muffler. It was making contact with the frame behind the bumper.

Novelty goat

Thanks. I just checked and the hangers are about 2 inches from anything else, so it looks unlikely to be the cause.

MaverickMLFD371

check your clamps....

Novelty goat

Clamps are tight as a drum. I went over everything and retightened, checked again and see nothing close to hitting anything else. Flummoxed.

mustangfan123

I can't think of anything as to what the problem would be besides what was previously said. Good luck finding out what's wrong, I'd like to know when/if you do.

DoctorQ

If you didn't take the "pre-load" off the over-axle pipes (at the mid-pipes), it's near impossible to get a true fit at the over-axle joints (where you clamp the boomtubes to the over-axle pipes). I had a metallic rattle/vibration at certain RPMs (1500-1800 range). So l loosened the over-axle clamps, then loosened the mid-pipe clamps(roughly center of vehicle). You'll get a lot of slop now in the pipes (this is also the best way to center the tips). With both sets of clamps loose (over-axle and mid-pipe), center your tips in the bumper cutouts (and make sure your axle-backs are completely indexed into the over-axle pipe notch). Grab a friend as you really need someone to hold the tips in position while you tighten up the clamps (over-axle clamps first, then the mid-pipe clamps). Good luck solving your issue.

Novelty goat

Turned out it was the rear hanger on the driver side muffler making contact with the piece that bolts onto the frame of the car.

theedge67

That's what I thought.

GONE_N_60

Was this sound at higher RPMS or all over? I'm getting a similar sound under hard acceleration between 4 and 5 grand.

Novelty goat

The sound would become noticeable with the slighest throttle pressure, and sometimes even at idle in drive.

GONE_N_60

Ah, this must be different sound for me then.

Welcome to the BoomTube Club BTW

Novelty goat

Thank you. They are the best "muffler" I have heard. Accelerating on the highway, top down, the sound is absolutely delicious.