Got all new bushings in the rear arms, one new u joint, but I still have a tiny vibe, galloping vibe as someone here called it, at 45 to 90 or so. All tires are balanced, front was realigned, and it has all new rotors and such on front. Inside mirror is steady, outside shows it abit. May not be much, but it bugs me.

Checked the driveline angles today, on a new four post drive on lift. It was pretty much dead level. This is with stock replacement rear springs, and the front lowered a bit.

The bottom of the oilpan and trans pan say dead level.

The front u joint and yokie shows 4 deg down. Driveshaft is 2 deg down to the rear. Rear axle is 2 1/2 deg up in the front.

From research, it seems like the trans should rotate up or the axle should rotate up in front.

Is this enough to vibrate noticeably?

Suggestions?

Next move is to get the driveshaft balanced, hopefully this week.

Doubt 1.5° difference's is causing your vibe.
Stock GM is more than that and has been for 40+ year's.
When you did the rear arm bushings did you tighten everything with weight on the suspension?
Did you install a poly trans mount?

It still has a stock style trans mount that came in the car when I got it. It was a six cylinder pg car, and someone set a 350/th350 in place, and welded the motor mount brackets on the k member.

I think it still has the orig six cyl rear and ds. The rear trans mount seems to work ok with the TH350. Going to check the yoke engagement into the trans also, but it does not seem excessively loose by feel.

The vibe seems to shake, shake, shake, diminish, and start over, forever. Shows in the hood, the outside mirror and seats. Steering wheel still has some of it, but that has lessened with the new parts.

Tires would be a single steady frequency I think. It has been there since I got the car, and is substantially less than before I took the 3 in spacers out from under the springs. That gave me the idea that it is in the ds area. The trans-ds-rear are also not in a straight line horizontally, but I am told that is normal for a Chevelle. I tightened all the arms with the car on jackstands under the axle. The only other remaining rotating items are the brake drums.

It will run 70-90+ mph for miles, and does not seem to have any tire issues at all., other than lack of tread and driver sense.

Have not pulled the rear cover, but will do that as soon as possible, since I have a seal leaking on the right rear brake.

Going to get the ds balanced asap also. The hurricane looks like it may hold me up a week or so. By comparision, my 4.10 geared Mustang will run 105 at the top of the track much smoother. Did it with a balanced stock ds and currently has the aluminum one.

Any other items to check?

Yes, it is in the higher than wheel speed range, from my sotp analysis. Kind of like the shaft goes out of balance, then reaches a limit and comes back, only to start again.

I have, at different times, moved the tires around, no change. I suppose it could be a ring gear or bearing issue. Going through stuff as best I can until I find it.

It still seems like it could be a drive train issue. The entire drive train was changed out in my '66 and I had all kinds of vibration issues. I read tons of posts and looked at various web sites on how to set the pinion angle. I changed the setting so many times and never made it any better. The more research I did the more confusing it became. A fellow TC member put it in simple terms and I followed his directions and the problem went away. He told me to forget measuring the angle at the tranny and front u joint. He told me to measure the angle at the drive shaft near the rear U-joint and the angle on the rear differential. The point where the drive shaft meets the rear end, via the u joint, should make a "V". The difference between the two angles should be 2 to 3 degrees. I am not much of a guru but this worked for me.

Yeah Vince ,it's usually that simple.

Come and go vibration can be a loose/worn trans bushing ,wear in rear yoke at u-joint connection or driveshaft itself. When you pull it to get it balanced,inspect these items.If the balance doesn't fix it,and all else is good and tight,have a new driveshaft built using the next bigger tube size.