Rattle/knock sound after warmed up

[Tom Tom Turbo]

I have a weird rattle or knock sound that sounds like it is coming from the passenger side rear of the motor or front of the transmission. It does it from around 1300-2200 RPM but goes away at idle or if you stand on it. It has plenty of oil and the motor has around 800 miles on a complete tear down and rebuild.

I have a 5 disk Vigilante converter and the trans has about 5k miles on a level 2 rebuild from a reputable 2004R vendor.

Thoughts? I'm going to check converter bolts when I have time.


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[John Larkin]

I think you are on the right track. Mine were loose back when, knocked like a hammer sometimes.

 

[BMR]

I would start with converter bolts. If those check out, I would say move on to the flexplate. If it's cracked, it will make noise as well.

 

[few87]

When I had a rattle/knock at idle in the same area you are talking about, it was the brick in the catalytic converter loose knocking around inside. But I don't remember hearing it when driving.

 

[Phoneguy]

You are probably right in checking the converter bolts but it could be the converter itself. Does it sound like marbles?

Bryan

 

[Tom Tom Turbo]

It sounds more like a downpipe hitting the frame (which isn't happening) or a very loud lifter ticking (also not happening). I know the pink Vigilantes were known for being noisy, but mine is purple, installed in 2004. Don't know where that falls....


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[few87]

I don't recall it sounding like marbles. To confirm that it was the catalytic converter, I just banged on it with my first with the car off.

Dave

 

[Phoneguy]

If you still have the heat shield on the AC box , check to see if it is making contact with the valve cover

 

[Tom Tom Turbo]

No cat or cat heat shield on the car anymore. I'll check the valve covers, although I've had 2 different height valve covers on the car recently and there was no change in the sound.


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[Tom Tom Turbo]

Converter bolts were as tight as I could reasonably get them, no visible flexplate cracks. AC box heat shield was firmly attached (noise sounds more solid that a heat shield rattle anyway). Do I maybe have a bad converter?


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[Rodney87GN]

You may just have to bite the bullet and drop the tranny to be sure the flexplate isn't cracked. That's what I ended up doing after chasing a similar knock/rattle.

This is how my flexplate looked...

 

[DarthBuick]

If I thought the converter was making a noise I would take the converter bolts out and see if rattle goes away. It is a easy way to eliminate converter or trans noises.

 

[Tom Tom Turbo]

Forgive my ignorance but how does unbolting the converter keep it from rattling? It doesn't do it at idle, only under slight load or when revved up in park/neutral after it is up to temp.


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[DarthBuick]

If the converter isn't spinning it can't rattle. It is one way to eliminate it as a source of noise.

 

[Phoneguy]

If I thought the converter was making a noise I would take the converter bolts out and see if rattle goes away. It is a easy way to eliminate converter or trans noises.

This is the fastest way to eliminate the transmission from the equation....

Bryan

 

[Pronto]

You may just have to bite the bullet and drop the tranny to be sure the flexplate isn't cracked. That's what I ended up doing after chasing a similar knock/rattle.

This is how my flexplate looked...

Wow.

 

[Tom Tom Turbo]

My flexplate looks 10x better than that....if no lines, cracks, scoring, etc. I doubt that is my issue. Probably this 5 disk Precision converter. We'll check it out this weekend.


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[Tom Tom Turbo]

Checked the bolts, nothing there and there were no visible cracks on the flexplate. Which means it is probably internal transmission. It seems to go away when the converter locks around 55 mph. It is moderately noticeable under light acceleration but goes away at full throttle and gets worse when you're out of the gas completely. I'll upload a video shortly.


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[Tom Tom Turbo]

First video is in park after 30 miles of highway driving, 2nd video is cruising along at 35-40 mph






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[Benched]

Balancer bolt? About 220 ft/lbs.