Transmission vibration?

The hard shift is probably 3rd to 2nd. Around 15mph? Your throttle lever is set a little advanced. Meaning it is not returning to the full forward position when you let off the throttle. (I like this setting for a firmer shift and better clutch apply under light throttle.) Could be it needs a return spring or adjusting. With the throttle wide open the lever on the trans should just reach its rear most point. No resistance on the throttle rod. As for the vibration I have a similar problem. Have not been able to pin point but check your drive shaft length. should have 3/4 to 1 inch available slide into trans. Any more either way is too much. Could also be the gear setup in differential is not a match for the torque of the engine. example back lash is too tight or too loose. An experienced transmission/drive shaft shop should be able to help diagnose. As mentioned before check the u-joints for binding and proper centering. doesn't cost anything to take it out an check the joint vs diag time. PM me for more throttle rod adjusting questions.