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I have much of the bouncing and the shaking and the very regular periodic vibration right btween 50 and 60 especially appparent on smooth pavement traveling at a steady pace- no vibtration in steering, just the body structure. I've read (maybe fron McMark) that this is indicative of bad ball joints. Does this sound reasonable? Thanks!

I'd check that all the wheels are balanced correctly first....Could also be a flawed tire with a lump or high spot in it.
Or bad CV joint...Could be a lotta stuff, but most likley you have a wheel out of balance, probably on the rear of the car.

How old are your wheel bearings?

I changed nearly everything on the front (tie rods, ball joints, wheel bearings).
The wheel bearings brought the remedy.

Ball joints and tie rod ends are easily checked by lifting the wheel and grabbing side to side, then top to bottom and pushing and pulling. There should be no play or apparent hitting when pushed side to side, top to bottom. You should only feel the movement of the steering column and/or shock play. Any play is an indication of something worn.

With my 71 without wheel centering rings, it is possible to put the wheel on and not have it be in the exact center of the hub assembly. This is a real problem when I have the tires balanced and rotated. The monkeys at NTB start all 4 lugs, then torque them down one at a time. If I have a big vibration after that, I lift each wheel until just off the ground, put my work light behind it and rotate the tire. I find the high spot, loosen the lugs and retighten and rotate again. This seems to happen often with my fake Fuchs more than with my old steel wheels.

Spoke.

thanks fellers. to answer some Qs,
no looseness is apparent in any direction when a front wheel is liftedand tested BUT
this began after I replaced front bearings and rotors. I have retightened the axle nut a couple of times trying to locate this looseness. How tight is right? There is definite resistance to rotation now. but with tire on, if I spin the tire it will rotate a few revolutions. Is this still too loose?
It seems to maybe come more from the back, so I'm gonna check CVs.
My 73 has hub-centric wheels, but I'm gonna do the flashlight test anyway.
I don't think it is wheel balence or roundness since the prob has remained through a tire change (all new Kumhos now), but I may check 'em too.

the front axle nut should be tightened to 1 ft lb (assuming the nut turns freely) . If the wheel still has noticeable play on the axle then your spindles are worn. attempting to further torque that nut risks disaster. More than likely at an inopportune moment.