Had that issue with bouncing and noise. New Mopar cable, new gear in trans and all.
Two things that fixed it for me. A good cleaning to start with and light rust removal and silicon lube on the unit. Dunked my input side only in evaporust then lubed. 90% better. Last part was the cable pushing hard on the unit. Re-adjusted the cable posistion to not press so hard on the back of the unit. Not sure if your 66 has the same platstic push type connection my 69 does but mine is quiet and smooth now.
