Ok, trying to figure out where to head with this one. At about 20 to 25 mph in any gear (both going up, steady state and going down) I am getting some pretty bad shaking. It seems to be coming from the front end. I just had the tires rotated and balanced and that didn't fix anything.

I know I need new ball joints, and the wheel bearings SEEM to be tight, but I only checked them by shaking the wheels. Any other places I should check before I dive into the ball joints?

 

Are both tires spinning freely? If not check your brake calipers. I just replaced mine and it went away.

 

Is the shaking only occurring at that speed? Not while going faster, nor at a stop while reving the engine?

Other things I've had that cause vibration/shaking were, strut tower bushings, transmission mount, engine mounts, driveshaft. But those things were a problem at any speed. There's more in the front linkage that is probably worn out. Have you put the front end up that have a look at the pitman arm, idler arm, the inner tie rod ends besides the outer.

 

Im thinking trans mount. Ive had 4-5 go bad in the last 3 years, and for w.e reason it always sounds like its in front of me.

 

Transmission mount is new, tie rods are new, transmission is a piece of crap that needs a rebuilt. I replaced the idler arm a few years back. I will look into that. Both wheels turn freely.

Everything is smooth at a stop while reving. There is no shaking until 20, and it mostly goes away after 25. There is a bit, but nothing bad.

 

Sympathetic resonance or harmonic vibration?

 

I found mine to be the axle, I disconnected the driveshaft to make sure there was no play in the clutch, transmission, or motor. No problems there, smooth up to 50mph

I reconnected the driveshaft and the vibration was there again so I knew it was the rear.

I took off the tires and rotors and my rear left axle hub was bent.
Now I have a new thirdmember and axles but my driveshaft won't bolt up smh, speaking of which I have to go make a thread about that now lol.

 

Sounds to me if your axle or hub was bent. You wouldn't be able to drive over 25 MPH. Lift the car up put it in gear. Watch the tire, and if the axle or bub is bent you'll see a major wobble. That isn't the kinda symptoms that creep up on you. Would have to be the result of hard impact. One part that you cant test easily, is the driveshaft. I had some vibration that was noticeable around 20-30 MPH. Than it would be only noticable to you if you are paying close attention to the ride.

The u-joints felt tight, but had a slight dryness feel while pushing the joints together while rolling the yokes back and fourth. I could identify the presence of high heat on the front ujoint, because the paint on the shaft was burnt off.

I had one u-joint, so i choose to replace the front. Turned out it was the cause of my vibration. I plan on doing the rear next. Seams like 30 years of heat on that joint burnt up the grease, and ran them dry.

Now with a new joint on there, I can feel a major difference in age.

 

Could very well be a u joint , they don't just wear out but also get dry and seize up ,if you have the shaft off make it move as far a possible in a circular motion ( both front and rear ,if there is any resistance felt ( a sort of grinding tight feeling then it is seized from lack of lubrication . most often this happens in wet climates . just because you can't feel any slop in the u joint doesn't mean they are good .

 

Ya my u-joints felt tight and had only very slight signs of wear. One good indicator of failure is signs of extreme heat. Try pushing the u-joint together and rolling it around. Lack of lubrication should be felt. Then try pulling the joint away from each other and roll it around again.

It will be hard to notice if you don't have a new one to compare it to.

Any play between yokes will cause some vibration. A good u-joint should feel as tight as a cats @ss.