Brakes and Tires
What would cause a vibration from 48mph to 80mph on a 1993 Buick Roadmaster wagon that has new rims tires auto lockout switch u-joints and drums and runs great?
Inspect the driveshaft, look for dents, undercoating or buildup,
or driveshaft or companion flange out of balance, check for missing
weights on shaft. Try removing driveshaft and reinstalling 180