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Vibration over 65

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Old 09-28-2004, 05:20 AM
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Default Vibration over 65

I recently had a 12 bolt with 4:11's installed. At the same time I had a Spohn adjustable torque arm and lower control arms installed. I did my 3 - 10 mile break in drives. And This morning I took it over 65 for the 1st time and once I hit 65 it felt like I had really nubby tires on the rear (like you would have on an off road 4x4) The car drives fine other than that. Could my TA pinion angle not be adjusted correctly?
Old 10-01-2004, 04:33 PM
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No one has any ideas?
Old 10-01-2004, 08:18 PM
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yes your pinion angle could have alot to do with it...
did you get your angle finder with the TQ arm?
there is differant settings for the street and strip
Old 10-02-2004, 08:05 AM
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Originally Posted by jaberwaki
yes your pinion angle could have alot to do with it...
did you get your angle finder with the TQ arm?
there is differant settings for the street and strip
THe shop that installed the rearend set the pinion angle, and they knew its for the street. Even if they set it for the track, I would have to let off of it before I hit the traps cuz of the vibration, I crawled under the car and noticed that the floorboard is dented from the top of the torque arm hitting it. I have not done any hard launches but I have got on it will moving. Would the dent be caused from hard acceleration or would the angle of the rearend change at higher speeds causing the torque arm to touch the floorboard and what I'm actually feeling is the road noise transferred thru the TA ?
Old 10-02-2004, 09:33 AM
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The dent is normal, I called spohn after the same setup without the LCA's. Spohn recommended making a dent in the floor board. I used a wood 1.5" railing and rounded off the edge so I wouldn't have a sharp dent. You'll never notice it inside since it's under the rear driver side seat.

As far as vibration, Mine vibrates at 75 MPH above. I lifted the rear and put the Pinion angle gauge on the TA mount to the diff and lowered the car back on a level surface and have 0 degree pinion angle. With the spohn rigid TA mount I think we're just feeling something that was always there, just the old TA tranny mount isolated it.

My next investment is going to be in a MW balanced DS. A lighter balanced DS should do the trick but I'm concerned about the CF DS mounts to the yoke. I'm thinking of doing with the 3" CM Balanced DS.
Old 10-03-2004, 03:51 PM
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I find it hard to believe that vibration over a certain speed is normal and should be excepted. There must be a reason for it, it can't be right
Old 10-04-2004, 05:38 PM
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ttt for ya
Old 10-04-2004, 10:26 PM
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I find it hard to believe that vibration over a certain speed is normal and should be excepted. There must be a reason for it, it can't be right
I never said it was normal, should be expected, or that it is right.

What I'm trying to get at is that aftermarket driveshaft suppliers may use more stringent balancing than a mass produced vehicle with rubber suspension mounts.

If you happen to find a solution, please fill me in. I would do the same.
Old 10-06-2004, 07:54 PM
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check the balance on your wheels. thats usually around the speed where a wheel imbalance wil be most prevalent.
Old 10-10-2004, 09:47 AM
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Got my car back from the shop. THey made the dent bigger, so the TA would not hit it. this seems to have done the trick. The "road noise" has decreased considerably.
Old 10-10-2004, 09:58 AM
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Crovax is right - vibes starting around 45-50 are usually driveline (driveshaft) related and starting at 60-70 are usually tire/wheel related. Could be bent rim/bad tire/out of balance combo. Hope for the balancing as it's the cheapest fix.
Old 10-10-2004, 10:25 AM
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Glad to hear that did the trick.



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