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Bad vibration over 60 mph

Street fighter

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I have a 73 charger that have a bad vibration at about 6o mph I have replaced rear tires after being told by two places that one of my rear tires had a flat spot on it, when I say a vibration I really mean a vibration that can be felt more when you get off the gas,I have what looks like some kind of a balancer on the rear of the trans that have two bolts that mounts to the trans, I noticed that the two rubber bushens are just about gone ,could this be my problem? I plan to check weight on the convertor and the balancer on the engine. what else could it be? also I will be checking the drive shaft weights. The engine is a 360 NEED HELP.
 
Can you shut it off at speed. Veer left right. Pop into neutral etc. Put someone in trunk.
 
I have a 73 charger that have a bad vibration at about 6o mph I have replaced rear tires after being told by two places that one of my rear tires had a flat spot on it, when I say a vibration I really mean a vibration that can be felt more when you get off the gas,I have what looks like some kind of a balancer on the rear of the trans that have two bolts that mounts to the trans, I noticed that the two rubber bushens are just about gone ,could this be my problem? I plan to check weight on the convertor and the balancer on the engine. what else could it be? also I will be checking the drive shaft weights. The engine is a 360 NEED HELP.
Is this on the transmission itself or on the drive shaft? Does it look like this? If it looks like the one in this picture its a parking brake.

IMG_1395.JPG
 
Rear pinion angle out of spec can do this. Search for threads on this and you’ll find an easy way to check it on your car. Good luck!
 
,I have what looks like some kind of a balancer on the rear of the trans that have two bolts that mounts to the trans, I noticed that the two rubber bushens are just about gone

Maybe transmission mount? If it's bad it could definitely cause a vibration.
 
Is this on the transmission itself or on the drive shaft? Does it look like this? If it looks like the one in this picture its a parking brake.

View attachment 720048
No it's not anything like that. it bolts on the tail of the trans and it have two 5/16 bolts that bolts it to the tail of the trans, each bolt is surrounded by two rubber bushings, it appears to be a counter weight for the tail of the trans to stop vibration.
 
360s are externally balanced so it's possible you have the wrong balancer or converter but I doubt it from your description because I think you would feel that throughout the rpm range. Vibration problems are really hard to diagnose. Mounts, tires and wheels, worn out front end parts, driveshaft, pinion angle all come into question. Process of elimination. Good luck!
 
No it's not anything like that. it bolts on the tail of the trans and it have two 5/16 bolts that bolts it to the tail of the trans, each bolt is surrounded by two rubber bushings, it appears to be a counter weight for the tail of the trans to stop vibration.

If the counterweight is loose, flopping around, it needs to be solid to do it's job. See if you can replace the worn out rubber.
 
360s are externally balanced so it's possible you have the wrong balancer or converter but I doubt it from your description because I think you would feel that throughout the rpm range. Vibration problems are really hard to diagnose. Mounts, tires and wheels, worn out front end parts, driveshaft, pinion angle all come into question. Process of elimination. Good luck!
 
It's very common for someone to put the wrong converter behind an externally balanced engine like the 360. That part you're talking about is a vibration damper. I've seen them before. First, you have to know when it's vibrating. Will it vibrate in park if you bring the rpms up? If so, the problem is in the engine/trans/converter. I have had converters fail internally, causing a vibration. Driveshafts have an oscillating rumble sound. Wheels and tires are more of a shake that you can almost feel each wobble. Check the trans mount. If it's bushings are gone, that could cause it.
 
Everything on the car is correct I have had it 30 years so I know it's none of those,I have a list of things that I am going to check and I hope that I can find out what's wrong, this can take some time the vibration is not coming from the front end steers great but you can feel it coming from the rear over 60 and slowing down from 60. BAD
 
It's very common for someone to put the wrong converter behind an externally balanced engine like the 360. That part you're talking about is a vibration damper. I've seen them before. First, you have to know when it's vibrating. Will it vibrate in park if you bring the rpms up? If so, the problem is in the engine/trans/converter. I have had converters fail internally, causing a vibration. Driveshafts have an oscillating rumble sound. Wheels and tires are more of a shake that you can almost feel each wobble. Check the trans mount. If it's bushings are gone, that could cause it.
I am going to try running it in park and check it. and see what I find ,I thought about the convertor so I checked the trans and there is no metal in it.
 
So let me see, the car was okay before but now it's got a vibration? Replace any driveline parts recently? Slap any curbs (not like that ever happens). Could be something simple like your driveshaft shucked a counter weight, U-joints taking a crap, or wheel weight shifted/fell off, maybe the slip yoke is giving up. If motor mounts and/or trans. mount are toast that can also give you grief. I'd start with the least expensive stuff first before I ripped into it. My 2 cents
Best of luck :thumbsup:
 
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I think if it was me I would remove the driveshaft to check the U joints for wear or one that's froze up.

Both my 73 Chargers had that cast weight bolted to the back of the trans. Even on the car I drove on the street (73 SE) I didn't notice the difference when I removed it.

Bryand
 
I would start with the drive shaft and go from there. you said it vibrates at 60 ,is that only when your accelerating or coasting ,did you put it in neutral to see if it would stop? So this is something new since you have had the car for 30 years. What did you change lately?
 
Anyone mentioned U-joints? My buddy had a bad trans mount and it caused the ujoint to wear out real fast. Had to replace both u-joints and a new trans mount. Fixed his vibration issue.
 
I just removed a 904 from my 74 Duster and I have that exact piece at the rear of the tranny that you have. I've put in a 727 and it doesn't have it. I looked in several books and there is no mention of that piece or even a picture of it on any trans. How about rotating tires front to rear to see if the vibration is now in the front. Do you drive car on a regular basis? Flat spots in tires happen from cars sitting for a period of time. Some tires are worse than others with flat spot problems.
 
Everything on the car is correct I have had it 30 years so I know it's none of those,I have a list of things that I am going to check and I hope that I can find out what's wrong, this can take some time the vibration is not coming from the front end steers great but you can feel it coming from the rear over 60 and slowing down from 60. BAD
First thing I’d do is crawl under the car and give either end of the drive shaft a good shake. If you get a bunch if shake at the rear it’s either the u-joints or your pinion bearings are going south. If it’s up front it’s either the u-joints or your slip yoke is shot. If everything seams tight it’s a good chance it’s mounts.
 
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