Driveshaft / U-Joint Tech 1967 Coronet 500

[ws27]

The unpredictable balancing just might be the yoke bushing, it can be replaced in the car.

[markz]

Didn't quite follow everything you said but...........

What were you trying to accomplish by the bump test? Resonance of the shaft? Not sure that would work. Using a software such as SimApp works well to determine the resonant frequency of the shaft.

Is this a stock suspension with a stock driveshaft?

I agree that a worn bushing may be the culprit.

As far as driveshaft angles, forget the equal and opposite rule for u joints that you understand.............. It ain't happening! Remember that the car driveshaft and rear leafs combine for a formula for significant dynamics. The angles are constantly changing. A four link or ladder bar suspension eliminates pinion rotation so they do not change angles nearly as much as a leaf spring suspension.

Because of pinion rotation, set the pinion down 5 to 7 degrees down relative to the driveshaft. The front angle should be pretty small - I believe less than 2 degrees but the service manual does not quantify the angle and I haven't ever heard of actual recommendations.

[Hibbing_Coronet_500]

I did a ring down test with my CSI 2120.
Yes stock springs no goofy stuff.

The car was born a small block. Someone before me put in a 383 using the conversion motor mounts.

Anyway.
My measurements are:
Transmission angle 2.6 deg down slope.
Drive shaft angle. 3.2 deg. Math equals .6 deg working angle.

Pinion angle 3.4 degrees up
Drive shaft angle 3.2 degrees. Math equals .2 degree working angle.
To make both equal and opposite I need to shim the pinion .8 degree down.

Thats the way I figure?

I also notice the when running on jack stands. If I pop it into neutral. The wheels don't coast. They slow down fast! With almost a slight growl coming from somewhere.

I need to hook up my vibe gear and use my head sets to listen for that growl.

Limmited time makes it hard to put everything together.

[Hibbing_Coronet_500]

My ambition with the drive angles is to ensure that they are close as can be. Then rule out drive angles if that stupid in and out once a second vibration at 63 mph goes away.
Process of elimination!

[markz]

Anyway.
My measurements are:
Transmission angle 2.6 deg down slope.
Drive shaft angle. 3.2 deg. Math equals .6 deg working angle.

Pinion angle 3.4 degrees up
Drive shaft angle 3.2 degrees. Math equals .2 degree working angle.
To make both equal and opposite I need to shim the pinion .8 degree down.

Thats the way I figure?

I also notice the when running on jack stands. If I pop it into neutral. The wheels don't coast. They slow down fast! With almost a slight growl coming from somewhere.

No! No! No! No! That will NOT work! You CANNOT have the opinion angle up or near zero! You MUST have a downward angle for the pinion compared to the driveshaft. Shoot for 5 to 7 degrees. I believe there is good writeup on that in the mopar chassis book. If you don't have a copy shoot me a PM and I will scan and email it to you.

I believe you are okay in the front.

You need to fix the rear angle. It will not work right with an upward or near zero pinion angle!

As far as the growling, probably just a tight brake shoe against the drum. Loosen the adjusters some and betcha it goes away.

Still think you might be fighting a worn bushing, but I would definitely fix the pinion angle first. Don't over-engineer this. I have been guilty of that sin myself in the past but as I get older I get smarter...............

[skeehorse]

http://www.macsmotorcitygarage.com/2014/...d-phasing/

[Hibbing_Coronet_500]

I found that article you mentioned. It states 5-7 deg downward pinion angle.

I would agree if this was a drag car Doing 9 second passes.
I took my 2.5 degree upward shims out and turned them 180 and added quarter inch shim under that to get to 5 deg downward angle.
No luck! The driveshaft binds and WON'T turn.
The car is still on jack stands and I did not attempt to operate it in this state.

I am waiting on a bushing kit and a set of 2 deg shims from eBay. Till then ill read and try any suggestions. Or listen to any advise out there.
It's frustrating when you take the steps to make the car "right" again. New this and new that. The car is getting tighter. Rides better etc. Just to be blessed with vibration issues that make the car worse than when it was as a sloppy bucket of bolts.

[markz]

I took my 2.5 degree upward shims out and turned them 180 and added quarter inch shim under that to get to 5 deg downward angle.
No luck! The driveshaft binds and WON'T turn.
The car is still on jack stands and I did not attempt to operate it in this state.

That is just not right. That is 5 degrees relative to the driveshaft right - not to level?

I will get under my daughter's car on Saturday and measure her angle. I forgot what it was, but I did check it. I used to run 5 to 7 degrees down in my race car when I ran it on the street. Was a leaf spring car then with SS leafs and a 8 3/4. Absolutely no trouble with it.

When you get into issues like this, it good to get back to basics. Make sure the bushing is good. Triple check the ujoints - look for looseness or binding. Recheck all your pinion angles - make sure you aren't overlooking something on how you are taking the measurements.

If all that fails, do a Kepnor Tregoe analysis..............

[markz]

You might try to remove the drums in case that is causing you binding or there is some issue with the wheels / tires.

[Hibbing_Coronet_500]

Update:
I got both pinion angles equal and opposite within .1 degree.
Test drive. Vibration 90% better, yet still there!

Ordering new Trans bushing and Trans mount.
Stay tuned.