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I'm working on a Ford Fairlane with a hella of a viberation. The 9" was overhauled using all new American parts by a good Ford line machanic working for 30 yrs. I have the unit on jack stands with the drive shaft removed, started car and ran the 4 speed through the gears. No viberations. Now the driveshaft was balanced and new U joints installed both ends. The only thing left that I can think of is the rear end. If you're thinking pinion angles, that could be it but how do you change angles. I've installed new springs and hardware [rubber bushings on top of springs] and am at wits with this Gal. Any thought about my problem?
 

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I had the exact same problem a while back.
I changed rear gear and bearings. It started to vibrate as h...!!
It turned out it was the driveshaft, had it balanced at a good shop...the vibration still there!! Put a dial indicator front,middle and rear at the driveshaft...result..they screwed up. They had some crappy tools when they balanced it they admitted so they redone it free at charge and it was better.

I did a roadtest, had my father tow me without the driveshaft in place so that way I came to the conclusion it must be the shaft.

Good luck.

André
 

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First off, what car are you working on?

Do you mean the drive-shaft was originally factory balanced or did you have it rebalanced and why? Remove the DS from the rear flange and rotate it 180 degrees and see if there is any change. Check the u-joints for freedom of movement while you have it pulled. Is the rear flange mounted correctly? Are the u-straps positioned correctly and did you torque them or just run them down?

Did the pinion angle change with the new springs?
 

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First off, what car are you working on?

Do you mean the drive-shaft was originally factory balanced or did you have it rebalanced and why? Remove the DS from the rear flange and rotate it 180 degrees and see if there is any change. Check the u-joints for freedom of movement while you have it pulled. Is the rear flange mounted correctly? Are the u-straps positioned correctly and did you torque them or just run them down?

Did the pinion angle change with the new springs?
BINGO! A good helpful thread from Kul finally :)
 
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