Any wear/play/slop in the drive train will show up to a certain degree as you describe. I would check universal joints, splined shafts, ring/pinion backlash, transmission wear.


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