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Extreme Veteran
Posts: 350
 
| Hi, has anyone experienced a vibration on acceleration? I have driven my 56 Dodge Custom Royal V8/auto approximately 300 Km (180 miles) and it has been as smooth as silk at speeds up to 100 kph(60 mph). Today I developed this scary vibration on acceleration be it from a stop or at a higher speed when I step on it. It feels like a rotary vibration but hard to pinpoint. U joints are both in good condition. Prop shaft couldn’t have just bent. Wheel bearing are all new front and rear and easy to determine if you have a bad bearing. So what is it? I’m stumped.
Del S |
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Expert
Posts: 2002
Location: Branson, MO | It could be trans/torque converter related but make sure it’s not an engine misfire of which it could be a spark plug or bad plug wire(s). Also (might be a long shot) but dirt/bad gas in the fuel system could be a contributor.
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Extreme Veteran
Posts: 350
| Hi, not a bad plug or wire. Idles smooth.....runs strong.
I never thought of the converter but will check it out along with everything else I can think of.
Thanks,
Del |
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Extreme Veteran
Posts: 350
| I forgot....I had tank cleaned and coated at a reputable shop. Have only added about 20 litres (5 gal) at a time until a few days ago when I filled up at a busy gas station. I hope I didn’t get the bottom of the tank. Will check it out.
Thanks,
Del |
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Expert
Posts: 2002
Location: Branson, MO | Don't be fooled, there is a big difference between idling and under load. I had the same situation and the car idled normally but under load there was a misfire. It turned out to be bad wires.
Whatever the case may be, good luck in getting it figured out. |
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Extreme Veteran
Posts: 341
Location: Wisconsin | A misfire could be one cause and I wouldn't rule that out, but I have twice had vibrations develop under acceleration with my '59 Fireflite and both times it was in the driveshaft. The first occurrence was due to a worn out front trunnion housing and that vibration developed over many miles of driving and gradually got worse. That repair was completed a year ago. Just two weeks ago, while at the National DeSoto Club convention, my car started vibrating extremely violently when accelerating. I actually also assumed it was a misfire under load and long story short is I am now good for another 10,000 miles before I need another tune-up with zero difference in how the car runs. Yesterday with the car home and on the lift, I took apart that front trunnion joint and found it was very dry. The factory manual warns against putting in too much grease due to the weight and the possibility of it throwing off the balance, but apparently I had skimped too much when I assembled it - a lesson learned for future reference. I took out the roller bearings and re-greased everything very well, put it together, and it's nice and smooth now. |
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Expert 5K+
Posts: 7393
Location: northern germany | Viper Guy - 2021-08-09 11:04 AM
Don't be fooled, there is a big difference between idling and under load. I had the same situation and the car idled normally but under load there was a misfire. It turned out to be bad wires.
Correct, had the same problem. Spark jump outside of the combustion chamber only under load.
An incorrect aligned rear axle (prop shaft) can cause bad vibration on acceleration also. |
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Expert 5K+
Posts: 7806
Location: Williams California | A broken transmission mount can cause vibrations similar to a bad driveshaft or U-joints. Causes misalignment of the transmission to differential.
---John |
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Board Moderator & Exner Expert 10K+
Posts: 13045
Location: Southern Sweden - Sturkö island | Good point John. Also travel, sand and other packed residue can make the transmission mount stiff and not flexible. Regering to the mount with spring |
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Extreme Veteran
Posts: 350
| Thanks people, I will take all suggestions into consideration when I get back to work on the old gal. Every suggestion makes sense, I just have to figure it out. Haven’t had time in the last couple of weeks.
Del S |
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Vibration on acceleration
