74 dart vibration problem.

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California Dart

California Dart

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Nov 6, 2011
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Location
Oceanside, California
So I bought this 74 Dart. Rattled like crazy on the drive home. I had the engine rebuilt, front end rebuilt, new shocks, New engine mounts and trans mount, alignment, new carb and this STILL vibrates with acceleration!!!! This is driving me nuts! I take it out at about 50-60 mph and then throw it in neutral and NO VIBRATION so it isn't the driveshaft. Has a 318/2 brl carb with the stock auto trans.

The engine rebuilder put a "motor home cam shaft" in it for better perfromance, hope thats not the problem. I can sit in park and accelerate and I get vibration. The motor is tuned and timed perfectly. What is my next step?

Do you guys think it could be the converter of flex plate?
 
Its possable someone put the wrong balancer on the engine, it might have a balancer from a 360 (which is externally balanced) on a 318 (internally balanced). If your balancer has half moon shaped piece of iron on the front it's for a 360 and will definatly cause a vibration if used on a 318.
 
daliant said:
Its possable someone put the wrong balancer on the engine, it might have a balancer from a 360 (which is externally balanced) on a 318 (internally balanced). If your balancer has half moon shaped piece of iron on the front it's for a 360 and will definatly cause a vibration if used on a 318.
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Yup, a 318 should have a symetrical balancer with no weights or cutouts. The same way with the torque converter......no weights. Hey, I just noticed that you're here in San Diego. Drive it by and I'll take a look/listen and give you my opinion. I'm in Spring Valley, how far away are you?
 
daliant said:
Its possable someone put the wrong balancer on the engine, it might have a balancer from a 360 (which is externally balanced) on a 318 (internally balanced). If your balancer has half moon shaped piece of iron on the front it's for a 360 and will definatly cause a vibration if used on a 318.
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don't you mean torqeconverter balancing weight?
 
philgorg said:
don't you mean torqeconverter balancing weight?
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You said that it vibrates in park and not moving, right? If you are in park the transmission is in park and you have the vibration it isn't the TQ or the driveshaft, neither one them is moving while in park. If you had the engine rebuilt have the shop check it.
 
The torque converter is definately moving in park with the engine running. It's bolted to the flex plate which is bolted to the crank. The stock 360 is externally balanced which means it uses external means to balance the engine. In this case a balancer with an oblong weight ('71-7) or hollow slot cut into the outer ring ('78-up) and a weight or two welded to the torque converter. A vibration sitting still in park and revving the engine indicates it's somewhere in the rotating assemby from the torque converter forward. This is assuming, of course, that the mounts are in good shape and nothing is hitting the frame and the exhaust is not rigidly mounted. Hopefully, whoever built the engine also balanced it or you're in for a difficult search.
 
cudamark said:
The torque converter is definately moving in park with the engine running. It's bolted to the flex plate which is bolted to the crank.
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thanks

i almost had a hernia from laughing on that one. :D
i should have went on to say that california should check the converter to see if it has weights on it. 318s and 340s did not have externally balanced TCs. most likely the car came with a 360. or if someone changed the tranny from a 904 to a 727 chances are they used one that was bolted to a 360.
 
The late '72 and '73 340 (cast crank) has a balance weight on the converter too. You could get a 904 or 727 behind a 360 and they both had balance weights.
 
the torque converter does move with engine running in park ? holy crap then i have issues ! LMAO
 
I don't know the history of what trans is in the car or what converter. I had the motor rebuilt, new mounts all around, new (hanging) exaust system and this still vibrates. It's either the converter, balancer, cam or the engine itself. It's not a huge vibration but it's there. I am in Oceanside California and I will take this anywhere around to get this solved. cuda mark can call me at 760-533-7946
 
I had a 74 340 Cuda that was internally balanced, and they threw a stock counterweighted balancer on it.......It did EXACTLY what you say.

After nearly pulling my hair out, I crawled under the car and looked with a flashlight (the weight is on the inside)..........and sure enough, there it was............In this case, I simply removed the counterweight (bolted), and got rid of the vast majority of the vibration.

I also had a car that needed a neutral balanced converter, and they put a new one on that was weighted..........Did the same thing..........A friend ground off the counterweight, and again, the vast majority of the vibration was gone.

You read about these vibrations constantly on these forums, and the majority of them seem to be an incorrect balancer or an incorrect converter, a counterweight being the culprit or the missing ingredient.
 
Well I had Cuda Mark look at it and he said the harmonic balancer looked ok and we really couldnt see the TC but noticed the dual exaust I had put on was pretty ridgid. The hangers have rubber washers but it's still very ridgid so I was told to put rubber hangers on them anyway. If that doesnt do it them I'm having this TC checked at a trans shop. Damm back keeps me from doing this stuff myself and this is getting real costly. I now have a 6500.00 ugly car that vibrates.
 
Well I have done everything but pull the trans on the problem. Just sitting there and giving it gas makes it vibrate. Either the guys rebuilt the motor unbalanced or theres a TC problem. Although when I stand above the motor and give it gas by hand, the motor looks and sounds smooth. would a speed shop be the best place to take this? and is there a good one near Oceanside, CA?
 
Had the trans pulled and the TQ spun and checked. TQ was 40 grams off so they added another weight right next to the one there already to zero it out. Only have vibration up to 2000 rpms and really not too bad. There's still a little vibration left and all we can see is that the main crank pully is a little bent and wobbles a little, but tight. Noy sure if that would cause the vibration though.
 
Glad to see its getting better Dana your packets headed in the mail buddy
 
California Dart said:
Had the trans pulled and the TQ spun and checked. TQ was 40 grams off so they added another weight right next to the one there already to zero it out. Only have vibration up to 2000 rpms and really not too bad. There's still a little vibration left and all we can see is that the main crank pully is a little bent and wobbles a little, but tight. Noy sure if that would cause the vibration though.
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There should be no engine balance weights on the converter at all on a 318. There could be some thin sheet metal type straps welded to the outer edge for fine tuning the balance due to imperfections in the manufacturing process, but that should be it.
 
cudamark said:
There should be no engine balance weights on the converter at all on a 318. There could be some thin sheet metal type straps welded to the outer edge for fine tuning the balance due to imperfections in the manufacturing process, but that should be it.
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I hear ya but that's what the trans guy said. Said there was one weight on it and when he spun the converter it was 40 grams off. He put another counterweight next to it and it's much better. The second weight was put right next to the existing one.
 
philgorg said:
thanks

i almost had a hernia from laughing on that one. :D
i should have went on to say that california should check the converter to see if it has weights on it. 318s and 340s did not have externally balanced TCs. most likely the car came with a 360. or if someone changed the tranny from a 904 to a 727 chances are they used one that was bolted to a 360.
Click to expand...
May have had a 360 in it at some point because there were indeed weights on the TQ.
 
cast crank = you must have 318 cast crank matched balancer + ***either*** weighted flex plate for 318 with a neutral torque converter (aftermarket) ***or*** the neutral flex plate with weighted converter(stock)

steel crank = you must have 318 steel crank neutral balancer + neutral flex plate + neutral torque converter
 
to keep it simple steel = all parts are neutral balanced this is called "internally balanced"

cast = balancer is offset (specific to engine, 318/340/360 are all different balancers) and one of the parts out back must be offset as well but not both and they cannot be neutral
 
after a little research, i belive all 318's were produced internally balanced... however, if someone put a 340 crank in that was from a later 340 it would need a correct balancer.

it could be that you have a 360 balancer on the front.
they look different. this page has pictures of the 318/steel340 as well as two of the 360 balancers
no picture of the 340 cast crank balancer
http://www.bouchillonperformance.com/BPEHarmonicBalancers.asp
 
moparlover said:
after a little research, i belive all 318's were produced internally balanced... however, if someone put a 340 crank in that was from a later 340 it would need a correct balancer.

it could be that you have a 360 balancer on the front.
they look different. this page has pictures of the 318/steel340 as well as two of the 360 balancers
no picture of the 340 cast crank balancer
http://www.bouchillonperformance.com/BPEHarmonicBalancers.asp
Click to expand...
Believe me. We have checked everything out twice. Everything is new. Correct non-weighted front balancer. The crank pully is a little bent but don't know if that would cause vibration. Just adding the second weight on that torque converter made a huge difference. Used to vibrate from 1000 to 4000 rpm and now only vibrates up to about 1500.
 
Well theres only a little vibration left. I was finally told today that it may be the slightly bent crank pully. Since mine wobbles a little bit and it's attached to the Harmonic Balancer a fabo member I met today thinks it's definately a problem. We'll see next week. Because it's being replaced with a brand new one.

So who sells brand new ones?
 
its in the motor or the accessories on the front . did you try undoing the belts one by one? 273,318,steel crank 340 no weights on the convertor.
 
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