Bad vibrations...

[miller]

Off hand, since all the work, only thing that comes to mind is, front wheel bearings. If you haven't already, pull all four, inners and outers. Should be completely cleaned, inspected, re-packed, and with new seals, installed right.
Do NOT mix any of the bearing races. They are sets. If something is bad, it will show.

 

[Dave145]

I forgot to add that I replaced all four front bearings and their races, along with both rear outer bearings back in June. I'm wondering if my rims are bent at this point.

 

[Dave L]

Now I just gotta source either a cheap 2bbl carb for her or rebush the throttle shaft in mine. The old Stromberg is a bit worn out and leaks there. Also need to determine why the motor shakes while accelerating in park with the front end on stands. Hoping it's just a weak coil causing breakup...

I've been reading your post.Maybe your stuck on your vibration being a suspension problem.You said earlier that your poly runs smooth now it not. I would look at a tune up, you may have a bad wire or a plug giving your headache

 

[MW 413]

Have you replaced the tires yet? I read in a prior post your tire treads were cupped. Being a little over size on your rims is not an issue. But cupped tires that will balance tell me the tires have separated belts internally and will become out of round at different road speeds causing vibrations that come and go at different speeds and road surfaces. You could also try airing your tires up to the max inflation marked on the sidewall plus 5 lbs and just take it down the road and see if the vibration changes. If it does it is definantly the tires. After all you have spent in the rest of this thread the tires are not that expensive. Not trying to be smart, just trying to help you resolve your issue.

 

[Dave145]

MW 413: that's a good idea! Looks like a logical trial. The tires are a year old. They were on another car of mine for 3,000 miles, then the car got totaled. A month later I transferred the tires to this car. They have some chopping due to the crappy alignment this car had, but I'm hoping to run them a bit to see if that will wear into line.

The car did run smooth...and still does most of the time. I know my low speed shudder is related to the carb, since it rolls at those speeds fine but shudders while I accelerate through them.

The tires are Cooper cobras. Heard lots of good about them, but they even vibrated at 70mph on my old car ('76 Dart 4 Door)

 

[oldbee]

First of all your tires WILL NOT wear-in to a good pattern, they'll always be "bad". If you raise the frt end and spin the tires you can usually see a broken tire belt/bent rim by a sideways jump of tire while it's rotating. I'm also thinking maybe ur pinion angle could be out of whack causing your vibration? Usually tires/rims are felt in steering wheel,floor vibrations are 'usually' mounts, rear end, drivetrain.

 

[MW 413]

Tires do not wear back in once they have started a bad wear pattern. Even when put on another vehicle. They will continue to wear in the same bad wear pattern and get worse. Just a dumb question but we're any of the 4 tires hit or slid for any distance during the accident? Another reason the plys may be separating in one or more of the 4 tires or flat spotted.

 

[MW 413]

Like Oldbee says, jack up each tire and lay a Wood block or something next to the tire and rim on the inside and outside of the tire and rim and see of the distance changes as you spin the tire/rim around. Sometimes though separated plys do not show up this way. They sometimes just grow at different rates when the tire is rolling on the highway causing vibration. Front tire problems will be felt in the steering wheel and rear tire and drive line vibrations will be felt in the seat of your pants. In large trucks I have had diff pinions bearings that were loose take all the drive belts off the front of the engine with no vibration felt by the driver.

 

[oldbee]

Yeah usually a bent rim is flattened where it hit something, that's pretty obvious but a broken belt in tire can usually be seen just by spinning a tire and looking between it and the ground.

 

[Dave145]

Well, that's not really good news about the tires. I've been told they will "learn" to be true again with a proper alignment, but if you say that's false then that's out the window.

The accident I mentioned was a rear end hit. I was stopped and a truck rear ended me. I don't believe the accident caused a tire issue, because they were trouble makers on the car that got hit too. I will check for the tire wobbles tonight and post back.

The car vibrated terribly when I bought it too. We figured the tires on it that we're 3 years old were bad and removed them. One rim has a small ding in the very lip of it, but that can't be causing this massive vibration.

Back when I was first troubleshooting the vibration I ran the car on stands and noted the rear tires wobbling in and out...attributed it to bad wheel bearings (they were making noise on the passenger side)...

 

[oldbee]

Now were getting to the root of the problem. Possible bent axle shaft? Again put it on a lift and run it; you should see something. I know, there's so many things to look for. Always remember,first&foremost- KISS. Keep it simple stupid. It works more times than not. Been there,done that!

 

[493 Mike]

Did you follow Oldbee's advise to check the pinion angle? When I worked at a dealership in the 70's I cured a new car's vibration by correcting the pinion angle. See the FSM.
Mike

 

[oldbee]

And now we know how old 493mike is, give or take! Ya gotta listen(sometimes) to the 'old guys'...

 

[Dave145]

I'd like to hope it's not a bent shaft...it's just a 318 car that has less get up and go than an abandoned wheelchair...

Pinion angle I can look into. Rear springs are sagging badly (they're flat). But I don't know how much pinion angle can change with that.

 

[oldbee]

Probably more than you think!

 

[Dave145]

Back with info.

Pinion angle is 3.7 degrees.

Held a Carpenters square to all tires. Spinning by hand, they look true to the square. However...

Right rear wheel appeared to have movement in the rim outer lip. Could see a bit of run-out. Tire looked straight while spinning.

Left rear wheel had no rim movement at all. Looked true. Tire wobbles side to side a bit though.

Checked driveshaft. Straight as an arrow.

The tires aren't chopped as bad as they were made out to be. The rears are worse than the fronts, but even then I have felt worse.

 

[64Belvedere]

What about a driveline alignment issue? You mentioned it goes away on deceleration. when you decelerate, the pinion angle would change a bit. You also said the rear springs are sacked. I wonder if there is play in the bushings that is allowing the rear to rotate to much and throw things out of alignment. I fought this battle on my 64 Belvedere a few years ago. I ended up putting a trans mount and a new driveshaft in and that fixed the issue. Where did you have your jackstands during the rear wheel test? Were they under the axle? As the axle moves up and down through the suspension travel, the u joint angles would change some as well. Just spitballing here based on my own experience.

 

[Dave145]

I had the stands under the axle. I'm a bit more worried about the rims/tires wobbling though. Took videos of each and it's not quite what I think should be normal. The tread itself moves side to side a bit on the left rear, and the right rear rim clearly has a waddle about it's lip.

 

[Dave145]

I should mention that when I measured the angle, I had the car in all four wheels on the ground.

 

[oldbee]

Try to sight between tread&aground and you shouldn't see any wobble. Maybe you have a bad wheel on one side & bad tire on other. It's exasperating at times.