Source of slight driveline (?) vibration on my 64 with TH400

[Norman Silverman]

Hello All.

Because i like my cars to operate as close to the way they did when nearly new, I chase almost everything mechanical. While I'm waiting for Russ' Comfortron book to arrive, I am thinking about the SLIGHT vibration(rumbling) my car experiences at speeds over 50. It is not the tires, of that i'm sure. It feels like a chassis rumble.

It is slight, but annoying-to me. If I give the car more throttle at 50 plus the vibration/rumbling seems to get just a bit worse. So, my thoughts are:

1) Failing Driveshaft center bearing/support. (I have Imperials and this is a common fault in them, too-but it does not feel like this, although the driveshaft center bearing in those cars are not fastened to the main backbone of the chassis, like in our cars). 

2) Failing CV joint(s)

3) failing U-joint.

In the past, when I had problems with CV joints in newer (1966) Caddies, I found that rebuilt joints never operated vibration-free, so I am reluctant to go that route. Is there a way to re-lubricate the joints without taking them apart?

4) MAYBE dry front wheel bearings, but I have not yet looked and don't think that's the problem because it does not present until a bit of speed. (yeah, I know; that's usually tires out of balance/out of round, but I watched each one being done on a freshly calibrated machine). 

Any thoughts?

Thanks

Norm

[Norman Silverman]

Thanks!

Shocks are good, as are motor mounts, but there is a familiarity to this vibration that leads me to believe this is driveshaft related-especially after watching Jason's highly informative video. (I looked in the help section for driveshaft/driveline, but didn't see anything. Forums is where it is, and that's where I'll also look in the future). This is a very knowledge-rich site and I appreciate it more and more as i become familiar with how to find things, or in this case when other members are kind enough to steer me in the right direction. 

Much appreciation!

[Norman Silverman]

Noted with appreciation and comprehension. Everything looked pretty tight there when we had the car on the lift to examine the exhaust system. 

[3ft7bqmb7dryo]

Norm, the driveline vibration is as you pointed out, with one more piece of the puzzle to add.  The rear lower control arm bushings get distorted due to the spring weight directly bearing down onto the control arm. That causes a change in the pinion angle, causing vibration.

Pull the drive shaft out and check all the components.

[Norman Silverman]

Hi. Tires are brand new Hankook Optima radials and balanced perfectly. I bought them because I have them on 2 of my Imperials and they balance well and ride well. The reason I mentioned the muffler place is that I was able to get under the car and look around, but I won't dismiss anything at this point. 

Everything on my car is stock, so that's not an issue.

As to the balance weights, my old tires had the original outer balance weights that were designed to accommodate the wheel cover teeth(I saved them but did not re-use them because they were heavier than we needed. Because they don't make those anymore, I had the shop put regular balance weights on the inside of the rims and adhesive weights on the outside. The tires and rims balanced VERY well and few weights were used. 

Thanks for the tips, I appreciate them very much.

Oh, one more thing: are re there Zerk fittings in the CV joints? I didn't see any.