Bad vibrations (part 3)

[Dave145]

I can and likely will. I've tried a few times in the past and it hasn't changed anything, but maybe that's because of the whacked out pinion angle.

It's supposed to rain here for the next couple of days (though the sky is Crystal clear now?)...so I will try and get a test in when I can.

 

[6PKRTSE]

Change you harmonic balancer (damper). I had a vibration issue once like yours that was worse at 65 MPH or so & changed & tried everything as you have. I changed out the 40+ old damper at that time & the vibration has been gone now for many years.
Fuuny thing is once removed I had the old damper sitting on my garage shelf with the hub side facing down, one day walking by it several weeks or months later I notice it actually separated into two pieces while sitting there.

 

[Dave145]

Well guys I'm back. No success. I reinstalled the old original driveshaft with the corrected driveline angles and it's still vibrating. Not quite as bad, but still quite noticeable.

At this point I think I'll rebuild the ball and trunnion joint with a rebuilt kit off eBay and get the shaft balanced and then try again.

While the shaft was out I tried to shake and wiggle the pinion and trans flanges. Nothing moves even a hair.

 

[beanhead]

Pinion angle is wrong. It looks perfect right now until you drive it. If your transmission is down 3 degrees your pinion needs to be down also as it will come up when you are driving. If your measurements are accurate you should point the pinion down by 1-2 degrees. It travels up 3-4 under acceleration loads and higher under heavy load like launching. You can get some 5-6 degree shims to point it down to try. I went through the same thing on my 64 polara. Check my thread in the last few pages where I install new perches to correct the angle. I used a proper angle finder though. I don't trust apps for this.
Mine is perfect now with the old drive shaft and the new conversion like you have.

Ya! This may not be THE problem, but ideally you want the angle parallel under acceleration... So at rest the pinion should be a couple degrees lower than the trans angle... again, it may not be the fix for your high speed vibration but it's definitely not helping...

 

[beanhead]

Well guys I'm back. No success. I reinstalled the old original driveshaft with the corrected driveline angles and it's still vibrating. Not quite as bad, but still quite noticeable.

At this point I think I'll rebuild the ball and trunnion joint with a rebuilt kit off eBay and get the shaft balanced and then try again.

While the shaft was out I tried to shake and wiggle the pinion and trans flanges. Nothing moves even a hair.

Running it with the angles that far out of whack could very well have compromised your U-joints, so you might as well change those too now that the angle is corrected. But, I would guess that since changing shafts caused you to at least notice some difference, you are closing in on the problem area...

 

[5.7 hemi]

Now are you comparing how your car is to a new car? Since you’ve done about everything to fix it, could be that your expectations are high for 50 year old car? I’m asking cause with all the advice that’s been given, there has hardly been any change.

 

[Dave145]

Yes there has been little change, but no I'm not comparing it to a new car. I'm comparing it to every other car I've driven of this vintage. No car of any age is supposed to shake the **** out of itself above 60mph, unless of course it's from the 20's or 30's when a horse could piss faster than a car could drive.

I'm going to have the original driveshaft rebalanced. I may also rebuild the trunnion again with new parts for good measure.

I looked into the trans out put shaft bushing. It doesn't have one according to all my parts books. 65 and up do. 64 and down don't. 62-64 transmissions have just two bearings in the tailshaft, so that possibility is out.