Drive shaft unbalance

[Paul G]

What is the symptom of an unbalanced drive shaft?

I had the Charger on the highway last weekend. Doing some shake out runs prior to the drive to Vegas. I am getting a vibration at speeds over 65 mph. It is an oscillating type of vibration I can feel in the floor and seat. At 65 mph it starts and gets more pronounced with more speed. At speeds over 65 mph, dropping it in neutral and letting the engine idle does nothing for the vibration until the vehicle speed gets back under 65, then it goes away. I would think that eliminates the engine and trans? I felt all around the drive shaft for a weight. It has one welded on it.

Tires? I have a new set of Firestones on order. The 275's are out of stock. Got to wait for another production run. My tires are 10 years old. Probably out of balance as well. Think it might all be in the tires?

[greenpigs]

Flat spot on tire(s)?

[bull]

Did you check the u-joints and trans output for excessive play? 

[Just 6T9 CHGR]

I had a similar vibration & mine turned out to be the pinion bearing

[Paul G]

Did you check the u-joints and trans output for excessive play? 

I wiggled the shaft around best as possible by hand. No play.

[68coronetGLwannabe]

Tires? I have a new set of Firestones on order. The 275's are out of stock. Got to wait for another production run. My tires are 10 years old. Probably out of balance as well. Think it might all be in the tires?
[/quote]

10 years old tires in this AZ heat. I would definitely be at the tire shop getting them checked out. My Buddy had a very similar problem with his 68. He kept driving it and blew a rear tire which wiped out his rear quarter panel.

[Long Island RT]

Could be in the driveshaft angles too.  I had a serous issue that was only resolved when I set both driveshaft angles the same, only in an opposite direction and preferably between 1/2° and 3 1/2°.  Mine was exacerbated because I have a 4:10 rear with overdrive - so around 65-70 I was spinning the driveshaft 3500 rpm.

When the front angle was off - I could feel it in my shifter (manual).  When the rear was off - I felt it in the seat of my pants.

good luck

[Paul G]

I had a similar vibration & mine turned out to be the pinion bearing

Is there an easy way to check the pinion bearing or does the diff have to come apart?

[Just 6T9 CHGR]

I had a similar vibration & mine turned out to be the pinion bearing

Is there an easy way to check the pinion bearing or does the diff have to come apart?

The only way I found out is when I had my SG rebuilt.....tried everything else in the book....driveshaft balance 2x, wheel balance, drive shaft yoke, u-joints, pinion angle etc.  The new pinion bearing along with the proper backlash helped in my case.   The car still isnt Lexus-smooth but 100% better than it was before the rebuild