If the alignment was/is not correct the tires may be cupping, it will shake one wheel in one direction then the other wheel in the opposite direction.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy