Cyclic Vibration 70 Challenger RagTop

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    Author Topic: Cyclic Vibration 70 Challenger RagTop  (Read 2328 times)

    Offline 70ChallengerRag

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    Cyclic Vibration 70 Challenger RagTop
    « on: April 23, 2004 - 09:20:24 AM »
    Hi Everybody,

    I wondered if anybody might be able to help me. I have a 1970 Dodge Challenger Convertible with a 318 and a 904 automatic trany.

    I have a very heavy vibration that occurs every 1 or 2 seconds while driving or sitting with the car in park. It tends to occur between 2500 and 3500 RPM's. It also tends to be worse in cold weather.

    I have no clue what it could be. We have swapped the engine, motor mounts, transmission and rear end and still have the problem. We even had the engine that we put in perfectly balanced.

    Any help would be greatly appreciated.

    Greg
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    Offline Pistol Gripper

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    Re:Cyclic Vibration 70 Challenger RagTop
    « Reply #1 on: April 23, 2004 - 09:53:11 AM »
    Quick question,  does it do it with the tranny in neutral ?

    P.G.
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    Offline 70ChallengerRag

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    Re:Cyclic Vibration 70 Challenger RagTop
    « Reply #2 on: April 23, 2004 - 12:28:53 PM »
    If I remember correctly, it does vibrate when it is in neutral as long as the RPM's are up in that 2500 to 3500 range.  However, if you are moving and put it in neutral, it doesn't seem as bad because it isn't transmitting it throughout the entitire car.

    We have replaced the flexplate, and torq converter with no noticable improvements.

    Thanks
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    Offline Chryco Psycho

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    Re:Cyclic Vibration 70 Challenger RagTop
    « Reply #3 on: April 24, 2004 - 12:24:12 AM »
    What parts have been used with both combos? does it misfire or just keep running smooth while vibrating? I`m thinking maybe the ign or a condenser dropping cylinders or a carb problem , if eithe r the ign or carb have been used on both engines  ???
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    Offline 70ChallengerRag

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    Re:Cyclic Vibration 70 Challenger RagTop
    « Reply #4 on: April 26, 2004 - 08:45:39 AM »
    The Engine runs smoothly while the vibration occurs.  The original engine was a 318 (completely stock) with a 2bbl carburator.  The replacement engine is also a 318 but has a Holley 650 cfm 4 bbl carburator and Hooker Comp Headers.  The transmission is a stock 904 automatic but is not the original.  We have replaced the torq converter as well as the flex plate and continue to have the problem.

    Is there a problem with aftermarket motor mounts.  At one time I noticed that the motormounts were different but then replaced thm both with "stock" replacements.  

    It can't be the tranny because when we were testing things we had a flywheel put in just so the car would be able to crank but would not transmit any vibration from the transmission (if there was any) but the vibration was still there.

    Thanks

    Greg
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    Offline torredcuda

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    Re:Cyclic Vibration 70 Challenger RagTop
    « Reply #5 on: April 26, 2004 - 08:05:01 PM »
    What type of exhaust sysytem do you have?Have you replaced the harmonic balancer and is it the correct one?Do you have the correct balance flex plate/torque converter?
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    Jeff
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    Offline Chryco Psycho

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    Re:Cyclic Vibration 70 Challenger RagTop
    « Reply #6 on: April 27, 2004 - 12:51:29 AM »
    Are using a clutch fan if so is it the same fan , possibly the alternator  loading & unloading ?
     Try running it without belts & see if the vibration goes away  
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    Offline oldvamoparfan

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    Re:Cyclic Vibration 70 Challenger RagTop
    « Reply #7 on: May 02, 2004 - 11:56:54 AM »
    TR may be on the track.  Did either torque conv come from a vehicle w/ a 360 engine?  Look on the engine side of the TC & see if it has a weight welded to it out near the ring gear.  If it does, you have a 360 balanced TC.  You can remove it, or get a 318 TC.  Also, did you use an after mkt flex plate?  It too could have built in bal wgts for 360.  The are not obviously different, so you would probably have to ck the part #. If so, a stock flex plt will fix your problem. Ck back side of  harmonic balancer to see  if it is even all the way around.  If it has cutouts, it is a 360 balancer.  Good luck & happy Moparring.   Ovmf
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    '72 Challenger 360,  '05 Dakota,   04 Town & Country,   '82 Yamaha 650 Maxim
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