Author Topic: Rear Vibration  (Read 1642 times)

Offline DukeOfHazzards

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Rear Vibration
« on: April 20, 2010 - 10:44:26 AM »
I took my 70 Cuda over to Dan Fast Brakes and Mufflers in Lynnwood, WA and Mike over there told me more about my ride in 5 minutes then I new about it in the last 2 months that I've owned it.  He told me that he knew this car very well and that everything inside was pretty much brand new since it was fully restored.  After test driving it he noticed that there was a little bit of a vibration or humming noise towards the back end of the car.  It is cyclic and sounds rotational so it leads me to believe it could be 1 of 2 things either the tires are causing the noise or the tranny/diff.  I don't think it's the tires because the frequency of the noise isn't happening as fast as the tires are spinning.  It's almost like twice per second.  It can be heard while driving in all three gears.  Any ideas what could be causing this vibration noise?  Also second question is the automatic 3 speed tranny seems to shift from first to second and second to third pretty late.  Mike said it probably just needs "adjusting"?  Everything in the car is pretty much new so what exactly does that mean?
1970 'Cuda
2DR HT Lime Light Green
8 Cylinder 383 w/ Indy aluminum block heads pushing 465HP
3 Speed Automatic
2 Year complete frame off restoration, numbers matching, transmission and rear diff date code correct
2.5" Exhaust, white leather interior, new suspension
Condition: 1.1




Offline Chryco Psycho

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Re: Rear Vibration
« Reply #1 on: April 20, 2010 - 11:49:24 AM »
it could be a U joint in the driveshaft
it could also be the tires , I have had numerous problems with BFG tires being out of round even when brand new I would change the wheels &  tires  first & see if the problem is still there
 you may need to shorten the kickdown linkage to the tranny slightly to correct the late shift

Challenger - You`ll wish You Hadn`t

Offline tactransman

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Re: Rear Vibration
« Reply #2 on: April 21, 2010 - 09:08:26 AM »
Make sure the caps on the rear u -joint have the clips on them to center it in the rearend yoke. I do not know how many times I have seen those left off on a u-joint change because they don't hold the cap in like the other side of the "cross".  :screwy:
Terry-tactransman 
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Offline shadango

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Re: Rear Vibration
« Reply #3 on: April 21, 2010 - 01:37:18 PM »
YIKES!   :22yikes:

I cant say that I know for sure that my clips are in there...dont remember putting any in.

Got any pics of what it should look like?  I cant figure how a clip comes into play.....?? :clueless:
« Last Edit: April 21, 2010 - 01:46:01 PM by shadango »

Offline wally426ci

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Re: Rear Vibration
« Reply #4 on: April 21, 2010 - 01:42:24 PM »
It could also be the axle bearing adjustment. Mine does this every 3 years or so.  :clueless:
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Offline barracuda7199

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Re: Rear Vibration
« Reply #5 on: April 21, 2010 - 03:18:31 PM »
YIKES!   :22yikes:

I cant say that I know for sure that my clips are in there...dont remember putting any in.

Got any pics of what it should look like?  I cant figure how a clip comes into play.....?? :clueless:
they are half round metal rings not real thick that clip on the cups for the u joint at the bottom near the center right above the grease seal. not a real clear explaination but about the best i can do. compare the front to the back you should see them assuming they are in the front.
Brandon

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Offline tactransman

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Re: Rear Vibration
« Reply #6 on: April 21, 2010 - 03:43:16 PM »
YIKES!   :22yikes:

I cant say that I know for sure that my clips are in there...dont remember putting any in.

Got any pics of what it should look like?  I cant figure how a clip comes into play.....?? :clueless:
Make sure ALL four of these are installed,not just the two on the shaft cups themselves. The other two center the u-joint in the rearend yoke.

Terry-tactransman 
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Union, Mo.
Give a man a fish and he eats for a day,teach him to fish and he eats for a lifetime.

Offline tactransman

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Re: Rear Vibration
« Reply #7 on: April 21, 2010 - 03:58:01 PM »
This type of yoke has "tabs" for the u-joint cap to sit inside of so the clips are NOT required. So no tabs,gotta have the clips. Tabs ,no clips required to center the u-joint on the rearend yoke.

Terry-tactransman 
Torqueflite/Automatic Transmission Specialist
Union, Mo.
Give a man a fish and he eats for a day,teach him to fish and he eats for a lifetime.

Offline MEK-Dangerfield

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Re: Rear Vibration
« Reply #8 on: April 21, 2010 - 05:31:30 PM »
The obvious is a bad universal joint or an unbalanced drive shaft causing the vibration. If you think it could be the tires, is it possible to swap the front and rear tires, or do you have bigger tires in the rear?

As for the late shifts, do you know if the tranny has a shift kit installed? These late shifts could be intentional if so, but as Chryco mentioned, a shortening of the kickdown linkage would soften it up. The linkage is adjustable.

Mike

1970 Challenger - SOLD
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Offline shadango

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Re: Rear Vibration
« Reply #9 on: April 21, 2010 - 10:24:25 PM »

Offline wally426ci

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Re: Rear Vibration
« Reply #10 on: April 22, 2010 - 08:43:07 AM »
I think thats the drive shaft, the yoke would be open (silver above)  :bigsmile:
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Offline tactransman

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Re: Rear Vibration
« Reply #11 on: April 22, 2010 - 02:56:16 PM »
Is that a picture of a yoke?
No,I tried to find one but couldn't. That is the driveshaft.
Terry-tactransman 
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Union, Mo.
Give a man a fish and he eats for a day,teach him to fish and he eats for a lifetime.

Offline Kevin71

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Re: Rear Vibration
« Reply #12 on: April 22, 2010 - 04:05:18 PM »
I had a vibration problem too.  It turned out to be the drive shaft was slightly off balance and it was to short.  I had swaped out a auto and put  in a 5 speed.  Had the drive shaft cut about 3/4' too short.  Magnified the off balance in the drive shaft.  I jacked the car up and put the rear end on stands and then put the car in gear and I could see what was vibrating.  Be careful don't want to get run over by your own car.

Offline RT Dude

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Re: Rear Vibration
« Reply #13 on: April 22, 2010 - 09:19:49 PM »
it could also be the tires , I have had numerous problems with BFG tires being out of round even when brand new I would change the wheels &  tires  first & see if the problem is still there
 
Had a similar vibration issue. Had the new 15x7 rims checked for concentricity, and they were all OK. Then checked out the new BFG tyres. They were over 10mm (3/8") out of concentricity  :22yikes: .
Had the tyres rebalanced and it was about 95% better.
Brent

Offline Kevin71

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Re: Rear Vibration
« Reply #14 on: June 09, 2010 - 11:51:37 AM »
I get up to around 70 and then back off a little,  getting a vibration.  If I push in the clutch it does it to. But when accelerating it's not there.  If lay completly of the gas it doesn't seem to be as bad.  Any ideas?