vibration from rear above 60

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skep419

skep419

5.9 Magnum 4 speed afficionado
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Last winter I replaced the torsion bar cross member and moved the springs in 3 inches. Went for the maiden voyage and noticed a vibration. I have changed the pinion angle from 4 deg negative to using the factory perch location at positive 2. Zero change in vibration. Transmission is neg 2. Yesterday I took of early from work and had the drive shaft balanced and new spicer u joints installed. Same thing. Tried a different set of rear tires. Checked the diff fluid level. Ran it on the hoist at work and it is coming right from the pinion. What else can I try? Before the changes there was zero vibration. Any suggestion would be greatly appreciated. Thanks
 
When you measure the angles are you going trans to shaft and pinion to shaft when the car is on the ground or on stands so front and rear suspention has full weight on it?
 
The car is on the ground at ride height with the driveshaft out. angle finder on the output shaft of transmission. pointing down 2 deg. Yoke has been at -4, -2, 0 , and now +2 (moved leaf springs back to factory perches to get the +2. all others were leaf spring shims.) No change in vibration. The driveshaft angles down to the rear from the trans 3 deg.
 
skep419 said:
The car is on the ground at ride height with the driveshaft out. angle finder on the output shaft of transmission. pointing down 2 deg. Yoke has been at -4, -2, 0 , and now +2 (moved leaf springs back to factory perches to get the +2. all others were leaf spring shims.) No change in vibration. The driveshaft angles down to the rear from the trans 3 deg.
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I know this is such a confusing issue. And many can't decide what is correct. But the way i see it, Trans at 2 and shaft at 3 means 1 deg down from tailshaft to driveshaft. You would want the opposite angle from the pinion to driveshaft. That would be under power, so if your springs allow 3 deg. of upward pinion motion under power you would want the pinion down 4 deg. at rest. I'm guessing on the pinion movement because the amount of power, pinion snubber settings and shock selection and/or settings can alter upward movement of the pinion. This is the way i've always adjusted mine but others may disagree, so let the beatings begin:violent1:.
 
That is exactly where I welded the perches after the 3" inboard kit (4 deg nose down). So I started putting shims in it thinking it was the angle causing vibration. That is not the case.
 
skep419 said:
That is exactly where I welded the perches after the 3" inboard kit (4 deg nose down). So I started putting shims in it thinking it was the angle causing vibration. That is not the case.
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Wow, looks like you did everything right. Maybe there is a issue in the carrier but im surprised it only started after your mods. Maybe someone else will have a idea for you:-k.
 
We tac welded the perches while it was bolted in the car. I then had a buddy bring it to work and have the finish welds done. Could the weld warp the tube?
 
skep419 said:
We tac welded the perches while it was bolted in the car. I then had a buddy bring it to work and have the finish welds done. Could the weld warp the tube?
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I wouldn't say that it couldn't, but i can't see just welding the perches distorted the tubes enough to cause a vibration issue?
 
Since you say it seems to be coming from the pinion area I wonder if this is just a front pinion bearing growling? I've seen pinion bearings growl pretty bad, almost to the point of feeling like a vibration. Have you tried turning the yoke by hand with the driveshaft removed? If so did it turn smoothly?
 
Had it up on the drive on hoist touching the case with my hand. No noise just vibration.
 
This may be grasping at straws, but could it be a shock issue. When you moved in the perches you changed the angle/length of the shocks. I know it's not likely but if they were long shocks(bottoming out) or worn?
 
When I get back to town I'm going to take the driveshaft out and have a buddy pull me down the highway. If it still vibrates I will disconnect the shocks and try that.
 
It could also be the trans output bearing or bushing. A problem there, would transfer into the shaft giving the illusion of rear vibration.
 
A bearing will make a noise, but not a vibration until the bearing is no longer able to hold whatever it is supposed to be holding.

Having a vibration above 60 without detail is of no help, i can't even begin to give you an idea without lots of detail of the vibration exactly.

when does it start, does it get faster, does it get stronger, does it go away after ___ mph...
We can not drive your car asking about a vibration online with the detail you gave will have you checking all kinds of nonsense and making all kinds of insane changes.

.
 
Sounds like it could be the tail shaft bushing
 
It starts at 60 gats worse the faster you go (vibration speeds up) vibrates on deceleration also.
 
How much play is aloud in the tailshaft bushing? It does have some movement
 
If there's enough play that you can feel it you should change it
It can be done from under the car if you get the right tools
One tools slides in and catches the bushing and uses a slide
Hammer to remove it and the other is used to drive the new
One in. I think the bushing is around 15.00
 
Supershafts said:
A bearing will make a noise, but not a vibration until the bearing is no longer able to hold whatever it is supposed to be holding.

Having a vibration above 60 without detail is of no help, i can't even begin to give you an idea without lots of detail of the vibration exactly.

when does it start, does it get faster, does it get stronger, does it go away after ___ mph...
We can not drive your car asking about a vibration online with the detail you gave will have you checking all kinds of nonsense and making all kinds of insane changes.

.
Click to expand...

[ame="http://www.youtube.com/watch?v=DFQHUrmiqJ8&feature=youtu.be"]YouTube[/ame]
 
Trying out different camera position on ride back. (nothing spectacular)

[ame="http://www.youtube.com/watch?v=u6LubBraIi0&feature=youtu.be"]http://www.youtube.com/watch?v=u6LubBraIi0&feature=youtu.be[/ame]
 
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