VIBRATION AT 50 MPH,1200-1500RPM
#141007
10/24/08 05:45 PM
10/24/08 05:45 PM
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Joined: Jan 2003
Posts: 568 Ormond Beach, FL
71STROKERFISH
OP
mopar
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OP
mopar
Joined: Jan 2003
Posts: 568
Ormond Beach, FL
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71 Barracuda, stroker sb/727/8-3/4 Got a vibration going on that occurs with trans(727)in neutral or drive. Vibration feels like it's coming from the convertor/trans/exhaust. I had the car up on the rack and nothing is rubbing, loose, obviously vibrating. In the past 2 months I've replaced the convertor with a new ring gear(checked the torque on the bolts...tight), replaced the stock ignition with a used MSD(great upgrade). I'm at my witts end with this. When I replaced the convertor I changed fluid....I've talked to many convertor and trans shops and they are saying it is not a convertor balancing problem.... Could the harmonic balancer cause a vibration at a specific RPM only...it's an original peice on this stroker motor from a 71 340..... Thanks! dougcataline@cox.net405-596-6513
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Re: VIBRATION AT 50 MPH,1200-1500RPM
[Re: 71STROKERFISH]
#141016
10/25/08 08:52 AM
10/25/08 08:52 AM
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Joined: Dec 2004
Posts: 1,061 New Mexico
dmerc
super stock
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super stock
Joined: Dec 2004
Posts: 1,061
New Mexico
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I had the same kind of problem and it turned out to be an out of balanced radiator fan, take your fan belts off and see if the vibration goes away. If it does, the problem is the fan blade, water pump or alternator. Something that the belts are driving. It's also possible to have an out of balance harmonic balancer but not likely.
Last edited by dmerc; 10/25/08 09:04 AM.
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Re: VIBRATION AT 50 MPH,1200-1500RPM
[Re: dmerc]
#141017
10/26/08 09:50 PM
10/26/08 09:50 PM
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Joined: Jan 2003
Posts: 568 Ormond Beach, FL
71STROKERFISH
OP
mopar
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OP
mopar
Joined: Jan 2003
Posts: 568
Ormond Beach, FL
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Well, sounds like I've got something else to look at now. Got the car outta the garage today, and did the following: Loosened belhousing boltls, started the engine: still had the vibration Loosened the transmount bolts, started the engine: still had the vibration Swapped out the ignition coil: still had vibration I put the timing light on it and had a closer look at the vibration RPM....it's more like 1900ish in park, neutral, in drive(power braking), on acceleration, and at 50MPH. I guess I'm going crazy here, but I plan to yank the fan and belts off next....what a headache! Thanks for the info so far folks!!! --71STROKERFISH
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Re: VIBRATION AT 50 MPH,1200-1500RPM
[Re: Exit1965]
#141019
01/10/09 10:01 PM
01/10/09 10:01 PM
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Joined: Jan 2003
Posts: 6,266 Renton Washington
Triple Threat
master
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master
Joined: Jan 2003
Posts: 6,266
Renton Washington
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Engine, Trans, flexplate or converter. If it will do it in neutral its obviously not anything from the trans back.
-Dustin 67 Dart, 9 second, 392" G3 Hemi 68 Barracuda 340 F/SA
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Re: VIBRATION AT 50 MPH,1200-1500RPM
[Re: Quikshft]
#141021
01/11/09 12:58 AM
01/11/09 12:58 AM
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Joined: Jul 2004
Posts: 12,812 Tulsa, Oklahoma
Wagonmaster
I Live Here
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I Live Here
Joined: Jul 2004
Posts: 12,812
Tulsa, Oklahoma
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Quote:
Don't laugh, but it simply sounds like a bad transmission mount. You've done so much trying to chase this down, try removing the mount and see if the rubber has degraded. When it fails it allows a metal to metal contact which will create a harmonic at certain rpm levels, regardless whether the car is at cruise speed or sitting at the curb in neutral.
I chased a vibration in the same RPM range for a couple years in mine. Had the carrier replaced, u-joints, shaft balanced, balancer. Turned out to be an UNBROKEN, yet old and hard trans mount.
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Re: VIBRATION AT 50 MPH,1200-1500RPM
[Re: Wagonmaster]
#141022
01/11/09 01:17 AM
01/11/09 01:17 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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I'm afraid to suggest it but I would pull the pan & see if any weight is laying in the pan/shake the rods & see if anything feels/looks amiss.
live every 24 hour block of time like it's your last day on earth
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Re: VIBRATION AT 50 MPH,1200-1500RPM
[Re: Wagonmaster]
#141024
01/11/09 09:19 AM
01/11/09 09:19 AM
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Joined: Jul 2003
Posts: 3,377 Rancho Cordova, CA
Exit1965
master
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master
Joined: Jul 2003
Posts: 3,377
Rancho Cordova, CA
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Quote:
Quote:
Don't laugh, but it simply sounds like a bad transmission mount. You've done so much trying to chase this down, try removing the mount and see if the rubber has degraded. When it fails it allows a metal to metal contact which will create a harmonic at certain rpm levels, regardless whether the car is at cruise speed or sitting at the curb in neutral.
I chased a vibration in the same RPM range for a couple years in mine. Had the carrier replaced, u-joints, shaft balanced, balancer. Turned out to be an UNBROKEN, yet old and hard trans mount.
I don't know about the original thread maker, but I am going to replace my trans mount today.
I'm using the red poly one, and I've done more searching and found that other people have the same symptoms with that stinking mount -- a pulsing vibration. I have a stock NAPA replacement I'm going to throw in there and will post back the results.
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