Bad knocking under feet

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ratty dart 340

ratty dart 340

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Hey everyone, I recently bought a 1973 dodge dart sport h code car from a yunkyard for 3k. She had been sitting for more than 20 years after the previous owner drag raced it. She has a ford 9 inch rearend that he had swapped into it, and he also swapped in a first year 360 for the 340. The engine runs amazing for the situation and does "drive." However, when we start driving around the neigherhood, there is a really bad knocking under out feet. Its definetly not coming from the engine, but maybe the torque converter and or flex plate is the problem? Somehow the tranny fluid was still in good shape after sitting so long but maybe the tranny is screwed up too. Its a 727 btw.


Also, when we press the brakes, the car wants to die. This seems vacuum related but i dont know.

Thanks, Andrew
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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.
 
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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Nope. No noise in park or netrual. The noise starts when the cars starts moving. Only recently did the brakes start killing the motor, when pressed. That is a seperate issue. As far as the noise, it sounds like a loose driveshaft wobbling, but we know for a fact that it's not the driveshaft.

I will try to get a video tomorrow.
 
I've "known so many things for a fact" through the years and had it wrong, it's pitiful, so keep an open mind.
 
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Check motor mounts etc, the exhaust could be "rocking" with engine.
Pop hood and have someone watch while u put it in gear.
 
Can you get the rear end in the air on jack stands? Running it in gear would let you see if it's a rear end noise, or if it's coming from upstream in the trans/TC/engine. Did you pull the rear brakes for a look? I had an old Ford wagon making a LOT of nasty noise due to an abortion of a brake job, it had a ton of noise from loose parts flopping around.
 
Does it have headers on it? Steve up there makes a great point. Most cheaper brand headers have trouble with torsion bar clearance and usually, it's more pronounced in gear if an auto.....but I believe you'd pick up on it at idle in gear. We need more pictures man. We love pictures. lol
 
halfafish said:
Can you get the rear end in the air on jack stands? Running it in gear would let you see if it's a rear end noise, or if it's coming from upstream in the trans/TC/engine. Did you pull the rear brakes for a look? I had an old Ford wagon making a LOT of nasty noise due to an abortion of a brake job, it had a ton of noise from loose parts flopping around.
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Yup. We have it on jacks and had to replace the drivers side drum cylinder bc it was leaking. But when in gear on the stand, there is no noise, which leads me to belive its further upstream.
 
ratty dart 340 said:
Yup. We have it on jacks and had to replace the drivers side drum cylinder bc it was leaking. But when in gear on the stand, there is no noise, which leads me to belive its further upstream.
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Tell you what try. With it on jack stands, put it in gear and get it up to where you hear the noise and gently apply the parking brake. That will load the drive train as if it's pulling weight. It may make it make the noise and person #2 can listen from under the car. Employ care, of course.
 
RustyRatRod said:
Does it have headers on it? Steve up there makes a great point. Most cheaper brand headers have trouble with torsion bar clearance and usually, it's more pronounced in gear if an auto.....but I believe you'd pick up on it at idle in gear. We need more pictures man. We love pictures. lol
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It does not have headers, just the stock manifolds.

We just did a front suspension rebuild kit and that fixed alot of knocking and bumbing, especially from some of the ball joints. However, this noise feels directly under the brake pedal. I have more pics of exterior/engine bay. But i will get some pics underneath.
 
ratty dart 340 said:
It does not have headers, just the stock manifolds.

We just did a front suspension rebuild kit and that fixed alot of knocking and bumbing, especially from some of the ball joints. However, this noise feels directly under the brake pedal. I have more pics of exterior/engine bay. But i will get some pics underneath.
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One thing to look for even on the stock exhaust is that driver's side head pipe coming off the manifold. It snakes through holy hell to get out of there. If it's a replacement from a muffler shop, it could be bumping against something. That's one thing to really look at closely.
 
Some more to check. Double check that the torque converter bolts are tight and they've not backed out. That can happen. Also get a light and shine up between the engine and transmission and look very closely at the flew plate. sometimes they crack and that can also cause some noises like knocking.
 
RustyRatRod said:
Some more to check. Double check that the torque converter bolts are tight and they've not backed out. That can happen. Also get a light and shine up between the engine and transmission and look very closely at the flew plate. sometimes they crack and that can also cause some noises like knocking.
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sounds great. I will test these things hopefully tomorrow. Our first thought was the flex plate being cracked or something.
 
Great find!!!!! I'd brought that biotch home too!!!

Dollar to donuts the knocking is your driver's side downpipe. But if that's the only real issue, you done good
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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 !
 
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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