A bad dampener is a bad dampener. Once they dry up they will not work again no matter how long anything warms up. The only cure is cganging it.
Common causes of a constant vibration are tires, imbalanced driveshaft, bad dampener, fuel injection system, bearings. Start with the tires and...
That is generally damaged belts in the steer tires. Insoect the steers or have them inspected by a shop.
