I looked again and found that he had stated the vibration is everywhere, I did not see anyone talking about driveshaft balancing. Has this been done ??

 

UPDATE and quick recap of Operation Parts Cannon. Vibration at around 75 ish with max intensity at 83. Feels like a wheel or tire is out of balance. As of today, I’ve have done and replaced the following: road force balanced new wheels and new Nitto 555 G2 tires, alignment, new wheel bearings, new tie rod ends, new shocks, new 6 u joints, new slip yoke, machined rotors, verified (new) brakes are not sticking, hoses not collapsed, e-brake not hung up. Took the old wheels and tires to get balanced and then put back on to test and same problem. The things I have NOT done are the front ball joints and suspension bushings because they are in really good shape as where most of the removed original parts.

I feel the vibration everywhere and its makes no difference what gear, what engine speed, idle and coasting, or braking. I have not had the prop shaft balanced. I was originally concerned that I may have flat-spotted the tires because the car sits for months on end. So I got some Flatstoppers and have used those for the last few years. What bothers me is that the old wheel and tires did the same thing. But for that fact, I would not have gone through all this. But everything is pointing to a wheel/tire issue.

So today, I will rig up a dial caliper that I got a Hobo Freight and will test the run out of all 8 wheels I have, and then figure out a what to test the tire run out. That should tell me loads of information. Until then, thank you all for your interest in my every descending madness. Dude.

 

Wow. That's a long read. Here's my take. I've chased a lot of vibrations in my years. First, don't rule anything out. Second, stop throwing parts at it. 3rd, do the obvious first. High speed vibrations are usually caused by a rotating part i.e. prop shaft, half shafts, rotors, wheels/tires. Based on what you've described here the first thing I would do is take all 3 shafts to a drive shaft shop and have them checked out for wear and balance. If all checks out, I'd start looking at that diff. Put in on a lift and run it up to speed. See if the vibration is there and is it worse when there is no load.

 

Please Forgive me if this was already discussed. Are you driving with the roof in-place & properly torqued? My car shimmies outrageously with the roof panel out. It just amplifys the whole mess. Top mounted, it's way reduced, even tolerable.

 

I mentioned driveshaft because I picked mine up from being balanced this past Friday and it was $80. I put a new yoke on it several months ago and new universals a year and a half ago. I had the original big a** weight on the yoke and thought it might need a "small" change to the weights / balance...... (see pic)
I wont get to drive until I figure out new or deleted cats.
.
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Roof on and tight. I cannot stand the way it drives with the roof off and the acrylic roof makes the car a greenhouse in the summer Florida sun.

 

Are your wheels the correct hub-centric size?? Just spit balling here. Its not "supposed" to matter, but I've seen where it has occasionally. Rare, but occasionally.

 

It would be worth having your alignment checked in the back, specifically camber. Since the half shafts use U-joints, any significant camber (positive or negative) will produce vibration. You might be able to get a general idea by just using a level placed vertically across the tire sidewall.

 

Found another anomaly doing the rear brakes. The left rear caliper is working properly, piston travels nicely, slide pins free, rubber hose okay, all is good...so I thought.

I went to replace the rear brakes (just because I’ve done everything else back there so why not) and noticed I could not get the left side to compress all the way to get the new pads on. Turns out, the person before me messed up the plate that goes under the piston, mechanically keeping it from going all the way down. There are two tabs that have to go through the top plate but are bent under the plate. In operation, the wheel is not stuck and does not get too hot. And I would never have noticed it but for replacing the rear brakes. This is something that could not possibly have happened on its own, and almost assuredly didn’t come from the factory that way. So, it had to be a Bubba. I took it all apart and fixed the problem, and the new brakes went on flawlessly. Now... I haven’t driven it yet (this was last night) but WTF are the chances that this little cheap piece of bent *** tin would be the cause of my madness and thousands of dollars, buckets of sweat, blood, and tears... Anyway, here is the picture, notice the left side and how it is crooked.

 

On a side note, I took off the spare tire for access to the rear, and liked the way it looks so I will keep it off. Here is a picture of all the bits that goes with the spare tire, the tray, its
brackets and bolts, jack and handle and hardware. This all comes to 43 pounds. So in a way, its like removing one of those (see picture below) from the back hatch area.

 

Fixed the brake issue, still vibrating. Tested all 4 new OE Brand wheels and two of the actul OE wheels for lateral and radial runout. See results. Its still vibrating between about 75 and is worse at 83 to 88. Yes I wish I could go back in time...

 

 

I've done alignments for years. I've never seen an alignment issue cause a vibration. If it's vibrating, there is something else wrong. If your camber is so far out that it causes the alignment of your half shafts to be uneven, well, you've got other issues still.

 

The camber adjustment on the C4 is a poor design and has been known to slip if not properly (heavily) torqued. The simple check I propose is easy and costs $nothing.

 

Update and diagnosis:

My brand new (in 2017) nitto tires with 2500 miles on them have all flat spotted, and they are permanent. The weird part of the vibration is that any one flat spotted tire may not be noticeable, but as they all rotate at different speeds, the flat spots come in and out of phase with one another driving me crazy and causing diagnosis madness. So after 700 miles I was able to feel when they would come in and out of phase with each other, both in the front or back and every once in a while it would feel like they would all four come into phas together and that's when I would notice the vibration at its worst. So, after all those new parts I threw at my car, it was the new “hi-performance” tires that did me in. I cannot blame Nitto entirely, as I did not drive the car that much, but I guess I should be storing my car on jack stands. Dude

 

I'm not saying this is impossible, but flat spotting modern tires is highly unlikely. And just from parking it, even more unlikely. Any possible flat spot from parking would work its way out in a few miles.

Now, I've seen flat spotting from locking up the brakes. But that has to be on a car without ABS.

 

Nope.

 

My Nitto NT-01s flat spot after sitting a few days. After a few miles, they smooth right out. Soft compound probably makes it more prone to it.
Scott

 

I got rid of a set of Nitto 555G2's because they flat spotted in 3 days so bad that it took 10 to 15 MILES of driving before I could go above 35 mph without shaking the car badly. SHAKING the car. NTSB warrantied them out.

A buddy of mine had a set of tires for his '90 permanently flat spot sitting over the winter here in Ohio. He had to replace them.

On my wife's Equinox, we returned a set of Coopers because they shook so bad, even after road force balancing. The Goodyears we have on now, one of them will flat spot if its sitting in a certain position. (in the last 2 months). Even the Cooper Zeons (which are not bad tires) that we put on the Corvette will flat spot a little. I recently bought a set of those devices to keep them round. The only salvation is I ge 25 to 35 % off because I am getting a pension from Goodyear and qualify for the retiree benefits.

Tires are just not what they used to be. Compounds are better, but back when men built the tires (at least here in Akron) they would make sure that belt ends didn't overlap, etc. Goodyear would cut their tires true round of there was an issue coming out of the mold. So many tires are now built overseas in plants either by machines that just do, or people that just do because they are making pennies.

 

Nope what?