Highway vibration that starts around 62mph. I do most of my own repairs at home, but I didn't do the engine replacement on this car..... But I'd researched how many other peoples Sevilles also have a highway vibration. Many claim tires and to stick with buying the original tires only. I think that's hogwash...

Many claim tie rod ends, motor mounts, front control arms need replacing, etc, etc, etc. But rarely was anyone getting it truly resolved.

I replaced all that sh*t, and still had a terrible highway vibration. But as I drive, I study exactly what I can notice about the vibration differently than most people. Heck my job is largely a problem resolver.

But I noticed little bumps or irregularities on the road, my vibration would go away as the suspension would respond only to that bump or irregularity. Only on completely smooth surface the vibration would start building and come back on.. This issue would clear up once I was over 80mph, but that's speeding in most cities. It was very irritating that right at the speeds we need to go around the city freeways, this thing would rattle your butt like crazy. Give me bumps and it would smooth out? Seems weird huh.

The vibration felt more like 2 sub-frame sections were battering against each other. Jacking up the car and studying what I could see looking under the car, the cross sectional sub frame across side to side in front of the back tires, was a separate sub-frame from the framework going forward with almost like big locate frame pins going up in holes that sit on rubber rings? I jacked up by the rearward sub-frame and saw these 2 frameworks start separating a gap to this rubber grommet. I think this was the problem. As I jacked up to open this gap, I grabbed 2 old unused 9/16th deep well sockets (1 for each side) and tapped these in against the 2 Sub-frames as wedges, dropped the car and went for a test drive. Cha Ching!!! That was the problem and my vibration was reduced about 80% less, which I could live with, but still not completely gone. But now the cars rear sits higher as the air compressor adjustable ride height is reading wrong, so I had to compromise that arm as well on the sensor so it thinks the car is already sitting high enough and stops running the compressor so much, lifting the car so high.

There has been so many things to make me hate this car..... But I love it's body style, it's power, and when the ride is smooth its amazing, I've never had a nicer riding car. But 4 years of owning it and I've spent nearly double in repairing things from the cost of the car, it's seriously been a love/hate relationship with a little more towards hate in that I wont buy Cadillac again. They have retarded design crap like this, and they leave common people who are not mechanically inclined to spend and spend trying to resolve issues because Cadillac won't take care of them.. That's bullshit...