what can cause violent rattling and vibrating and random speeds out of no where? It doesnt do it always just sometimes ill drive down the road and it will start out of nowere feels like all four wheels are about to fall of shakes the whole car. Things i looked at so far all four wheels are balanced front tires are brand new. the rear tires are et street dot slicks. All the steering components are tight and greased. All mounts are new and tight. Shocks and springs look good and all the bolts are tight in the suspension and chassis. Any body have a suggestion tommarow im going to put regulator 5 spoke z28 wheels on it to see if it makes a difference.

 

I have the same problem, cept i changed alot of stuff, guess im just gonna have to change out the whole under engine setup.

 

mine ended up being flat spots in my slicks

 

I had a similar problem, it ended up being the torque converter. When it would lock up, it would shudder pretty bad. It was intermittent though, but once the converter was changed, problem solved.

 

Mine ended up being flat spots on my wheels! Yeah, my wheels were not round. I had awful vibration from 45 to 55 MPH and a general bounce at all speeds.

Cars this heavy should like like my name (a Cadillac).