Bad knocking under feet

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Topless69 said:
After seeing under the hood, I’d say beavers.
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:rofl: Well, I was thinking along those lines too but I imagine they got it cleaned up pretty well from the sound of their efforts. But those are also very good suggestions on the exhaust head pipe, flex plate, and the driveshaft length. Get the car up with full weight on the suspension and confirm you’ve got around an inch or so between the u joint yoke and transmission rear seal. Setting up a mechanical oil pressure gauge would be a good idea too. I’ve got the same situation going on right now with main bearing knock in a dodge 239 v6. It’s usually in a low rpm situation with no throttle in neutral after it’s hot and the oil pressure bottoms out. It’s way past rebuilding but it’s turned into an experiment of how long one can go before it ends itself at this point.
 
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Rmoore said:
One other thing to check… Make sure someone hasn’t put the wrong driveshaft in this car ! If the driveshaft is to long , the slip yoke is being shoved up to far on the output shaft, slamming the slip yoke into the back of the output shaft ! That could be why it doesn’t do it with the car in the air ! Some thing else to look at Sir !
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Well being that the previous owner used the car for drag racing, and swapped the rear end. He may have also swapped the diveshaft, so i will def take a closer look at that. Thanks
 
Garrett Ellison said:
Oh wow, you had me at Dart Sport! Does it still have those tires and wheels on it and are they showing any signs of rubbing anywhere? But you also mentioned the 9 inch. Good chance the driveshaft length isn't correct. I had a 1980 firebird that had too long of a driveshaft in it that did the same thing.
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Wow very interesting. I will take a closer look and see if that could be the source of the knocking.
 
Topless69 said:
After seeing under the hood, I’d say beavers.
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Dont worry. We cleaned it.
k.JPG
 
Garrett Ellison said:
:rofl: Well, I was thinking along those lines too but I imagine they got it cleaned up pretty well from the sound of their efforts. But those are also very good suggestions on the exhaust head pipe, flex plate, and the driveshaft length. Get the car up with full weight on the suspension and confirm you’ve got around an inch or so between the u joint yoke and transmission rear seal. Setting up a mechanical oil pressure gauge would be a good idea too. I’ve got the same situation going on right now with main bearing knock in a dodge 239 v6. It’s usually in a low rpm situation with no throttle in neutral after it’s hot and the oil pressure bottoms out. It’s way past rebuilding but it’s turned into an experiment of how long one can go before it ends itself at this point.
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Loving all the ideas. Sounds like a great experiment
Thanks
 
RustyRatRod said:
Gosh, could be lots of things. ANY noise at all in park or neutral? How about when you are idling in drive and load the brakes? A video with some GOOD audio might help.
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I knew a guy that took a A/C duct rated 24" HD zip tie to a buddies driveshaft.... and NO, not mine... People know better, if they know me.... and AIN'T NO WAY I would mess with someone's Ride ...
 
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ratty dart 340 said:
but we know for a fact that it's not the driveshaft.
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Great Score. Did you have the drive shaft out when checking it? I don't know your skill set but a frozen u joint wont have play in it but has the potential to make a banging sound once driving.Just a thought. Also maybe unplug and cap your brake vacuum booster hose and see if it still stalls out. Just don't get yourself hurt.
 
Years ago, 1973 Gremlin 304 automatic, developed knocking under feet like 2 hammers drumming on the floor. Neck on torque converter was broken.
 
I've heard engine knock that turned out to be 3 loose flex plate bolts . 4th bolt hole on flex plate was broken off and missing.Doesn't sound like your issue but It can't hurt to remove the inspection cover and take a look.
 
4spdragtop said:
Check motor mounts etc, the exhaust could be "rocking" with engine.
Pop hood and have someone watch while u put it in gear.
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Like many others who "liked" this one, I'm with Steve. The engine or transmission mount is broken. The engine one definitely creates a thud that goes through the frame and will feel under foot. I've had one.
 
A loose or missing TC bolt I would suspect first. Another out of the box thought might be a worn out thrust bearing. Maybe hold the brake and raise the "in gear" rpm a bit.
 
You got it cleaned up purdy dang good!
 
Old engine mounts will cause this, I recently went through this on a 69 Polara that I had just purchased.


Alan
 
Your mounts are most likely spool type mount but can rattle if the rubber is rotten or worn out of them.
s-l300.jpg
 
Nice car.

When exactly does it clunk or knock?
Under load? while coasting? Turning?
Stopping? Bumps on the road?

Is the noise rpm related, does it speed/intensify with more gas pedal?
 
Kendog 170 said:
Great Score. Did you have the drive shaft out when checking it? I don't know your skill set but a frozen u joint wont have play in it but has the potential to make a banging sound once driving.Just a thought. Also maybe unplug and cap your brake vacuum booster hose and see if it still stalls out. Just don't get yourself hurt.
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We capped the brake booster where the vacuum line attaches awhile ago, but the car recently started stalling when pressing brakes. Which is wierd beacase we hadnt done anything to the car that would have made it do that.
 
Kendog 170 said:
I wish I scored that. I would covert it to a Demon style look but that's just me. Great car as is to play with.
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Yea we arent sure yet. We got really lucky with the price and condition. Its a perfect ratty muscle. We want to clear coat the patina and jf8 green paint. And also put some raised white lettering on it.

Really cool that this car has AC, power steering, power front disc brakes, performance hood treatment, H-code, and the rare rear fold down seat for this year.
 
69cudaownr said:
Like many others who "liked" this one, I'm with Steve. The engine or transmission mount is broken. The engine one definitely creates a thud that goes through the frame and will feel under foot. I've had one.
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Another good suggestion.

Thanks
 
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